classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: john11668 on October 23, 2019, 11:20:25 PM
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This is about the bike we converted to electric start, which for about a year has run sweetly with no significant problems. http://classicmotorcycleforum.com/index.php?topic=5722.msg26756#msg26756
Recently it started spluttering while out on a run and had to be recovered to the workshop .
We found that the clamp retaining the dynamo and Mag had worked loose allowing the dynamo to move, and we wondered if the timing might have jumped a tooth and set about checking.
It asks for 7/16” before TDC at full advance . We found it at about 1.7” so adjusted back to 7/16". It then would not start at all. Changed the plug and got it to fire but was still running rough and popping back through the carb. No matter where we set the advance lever , it still backfired when we eased the choke back to normal running position.
Then tried at 7/16” btdc with full retard, (on the basis that we could advance it on the lever to find a sweet spot.) We were unable to find a point where it would run without choke, yet without popping and flashing back through the carb. Full advance takes it to about the 1.7” btdc figure , which is where we found it.
Turning to carburettor we tried all the needle positions of the carb ( Amal 928) and no improvement. Just a bit more smoke at highest needle position
Even tried a new carb which does exactly the same . I know the proper carb should be Amal 276 but the bike had always had this one and it has run well since we recommissioned it .
We have checked compression (115-120 psi cranking). We have tried a couple of new plugs too. Contact breaker points gap is 0.012”
Despondency is starting to take hold of us .
Can anyone point us in the right direction. If we are going wrong we just cant see where.
Any assistance will be much appreciated
John
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Sounds like you got a blockage in the fuel somewhere.....is there a fine gauze strainer in the threaded connection to the tank.......might be blocked........anyway ,check the fuel flow to the carby ,with the cap on the tank(sometimes cap breathers cause problems).....also possible the capacitor in the mag has given up ....or even the windings ....but replace the capacitor first.
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Yes, are you sure that a flush of rust particles hasn't come down through the fuel system,
this creates problems like you describe - and it can take a significant amount of cleaning
to ensure they are all gone and all the jets are clear. Particularly on the idle side of things.
Did that 1.7" inches of advance correspond to one tooth out on the timing chain ?
I'd triple check that your spark advance is still where it is quoted it should be, too much spark
advance can't be tuned out and could present as if it was too lean.
So might it be if it was too retarded too ?
Remember, 90% of electrical problems are carburettor, and vice versa !!
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Gear train to mag.....if it has "jumped" one tooth ,then the gears will be a mess.......must say Ive been inundated with silly timing claims by newbies who dont know how to remove backlash before checking the timing........One even asking about his car,I could clearly hear the clatter of valves hitting pistons ,cambelt timing one tooth out.......he says he cant do it any better......must be the engines fault.............Good story tho....millenial says "can you have a look at my car?".......No ,I dont know nothin about cars....."What kind of mechanic are you ,doesnt know about cars"......".A bl**dy smart one." sez I.
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Tank has a new tap and filter , and we have been testing on a seperate (lawn mower) tank. Much easier to to measure 7/16" Btdc with tank off the bike .
Clear plastic pipe and new banjo filter so pretty certain we have got control of the muck. Added to new carb which is also spotless and behaves just the same.
Am now wondering whether to go back to 7/16" on full advance and another new plug just in case we had a duff one .
What is the best plug for a B31
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By fannying around with the carb settings you've introduced a lot more variables though.
If the problem was slipped timing then that's the area you should have concentrated on especially if the fuelling wasn't giving concerns before. Don't know the settings for a B31 but 7/16 sounds a lot. Just set my Star Twin at 5/16 as per the book.
I'd recheck the timing personally. BTW have you done the timing successfully in the past, or is this a first time for you?
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Gear train to mag.....if it has "jumped" one tooth ,then the gears will be a mess.......must say Ive been inundated with silly timing claims by newbies who dont know how to remove backlash before checking the timing........One even asking about his car,I could clearly hear the clatter of valves hitting pistons ,cambelt timing one tooth out.......he says he cant do it any better......must be the engines fault.............Good story tho....millenial says "can you have a look at my car?".......No ,I dont know nothin about cars....."What kind of mechanic are you ,doesnt know about cars"......".A bl**dy smart one." sez I.
As you say John K , B31 has a gear train . but there were no signs of damage. I dont think the mag pinion would have slipped on the taper seat either as it was pretty tight, but when the books say 7/16" and we were looking at 1.7 inches something must have moved. I inderstand 7/16 equates to about 38 degrees (which seems a lot) , no Idea what 1.7 " equates to but must be close to half the stroke so say 90 degrees , so something has to be well out of kilter .
The mag on these is held down on shims by the dynamo clamp and even with all tight there can be lateral movement between the gears which can be seen if you Jam the gears with a screwdriver blade for final tightening . Under normal circumstances the backlash is low so wouldnt expect it to give more than a couple of degrees error btdc. We did however try to ensure that the backlash was "taken up " as we clamped the pinion back on.
We are not really newbies , but would own up to being unfamiliar with B31 mainly because we have had no trouble up to press.
Is the figure of 7/16" btdc correct ? and should this be a full advance figure? If so with the range of movement on the plate cam this would take us well into the retard range if AR lever is at full retard .
I think we are back to original carb settings Rex but I tend to agree with the fannying around remark. Being honest it was other "experts" who introduced that element. Timing (on this bike) was a first for us cos it gave no problems previously and I have to say I was a bit rusty, but we made a proper puller for the pinion and the fag paper is released at the 7/16" point. .
Will go back to that figure at full advance , and try again with a new plug.
Were working to the following docs , but started to wonder whem the bike would not start after this procedure
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The backlash in the timing gears for this single cylinder mag (MO1L?) has always been it's problem, and I'm sure there used to be shims available to put under the mag base to reduce it.
That said, as long as you wind the engine backwards far enough, then forwards to the correct timing point (always full advance) the backlash shouldn't matter. It's not a track Goldie after all.. ;)
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Hi All,
Check for any end play or vertical movement of the magneto armature in its housing, running with a loose mag will damage the bearing insulators
If the armature has movement timing is impossible without first getting this sorted
B31 has usually a tight wire for full advance magdyno, so the timing must be set with the cable pulled all the way
then set points opening to 7/16in BTDC
If the mag has been left run loose it will damage the fixing dowel location slots in the crankcase
then tightening the strap will pull the unit towards the engine causing too tight a mesh and a gear "whine" when running
A dodge is to wedge the mag body back so the shaft is central in its oil seal housing by fitting an alloy strip of suitable thickness between the mag and strap at the base of the mag
run a strip of paper through between the mag and idler gear while turning the engine, it should be deformed but not cut into tiny strips
Then if necessary place shims as required to correct the gear mesh between crankcase and mag body
£1 to penny the mag is in trouble
John
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I think that extra shims would increase the backlash Rex, but backlash seems fine here so will try again at 7/16" , then turn it onward (manually) a few revs to check that it is releasing the rizla at the correct point each turn. That should make sure the backlash is taken up properly. I have a "C" spanner which allows me to turn it directly (on the crank) and fairly precisely . Then will try starting with new plug and report back. May even add a degree wheel onto the attached stub shaft so we can see what is going on.
Thanks for all the input . Am sure we will get there in the end .
I think one of the great things about a forum discussion is that it really does help you to get your own thoughts in order
Thanks for your recent contribution chaterlea. While we do the above will take the mag pinnion right out and have a close look. The backlash seems reasonable and there is no discernable whine but will have a close look at the mesh with the strip of paper. As I said before there appears to be a small amount of flex apparent when you jam the gears to tighten the pinion onto its taper. As you say it is tight wire .
After timing is it reasonable to start with full retard, and then advance a bit once running?
If it turns out that mag is damaged are parts available for DIY repair
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Not knowing what sort of ignition you actually have, as a general rule, a lot of Lucas type magnetos and magdynos
won't give a decent spark if you give it FULL retard.
Best try half retarded, unless that causes some kickback.
In which case you need to kick it harder !!, after decompressing of course.
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We dont do kicking R.
Bike has electric start . It usually starts with no problems just coughs and splutters back.
Are we generally of the opinion that running with more than the 7/16" BTDC advance will cause the spluttering and popping back which the thread is all about
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mention of jamming a screwdriver between gear teeth to tighten/loosen the nut,then mention of "flexing" of the magneto shaft............hopefully .being aware that the mag shaft is a stub press fitted into a brass armature end,and quite easy to bend /make loose in the brass piece.......the catch being the brass piece is a matched assy with the rest of the armature,and wont be amenable to individual parts swapping........moral of the story being you cant fix cuckoo clocks with a pipe wrench,not very well anyway.
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Valid remark john K but instructions do say that you should not hold the CB rotor with a spanner due to weaknesses in the shaft .
So how else do you stop the mag shaft from rotating while you nip the pinnion onto the taper .
We are engineers! We are not talking about swinging on a Stilson wrench here, and the clamp holding the mag dow in is hardly the most positive fixing so a bit of flexing was not a surprise!
Please tell us the correct way so that we avoid future mistakes as this pinion may have to be pulled off a time or two yet.
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Personally I loosely fit the timing pinion, and with the engine at it's correct firing point BTDC and the lever at full advance (plus points just opening obviously) use a suitably large socket to give the timing pinion (not the shaft!) a light tap to lock it onto the shaft, recheck the settings and if all OK then tighten the mag pinion.
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Likewise rex .
We made the puller but with the puller in place in the pinion and the jacking screw backed off a light tap on the end beds the pinion onto the cone. But how would you suggest to prevent the pinnion frpm turning while you nip it up.
Ours was prettty tight when we first came to pull the pinnion and while we havent "strangled" the nut up since it is natural to ensure it is tight ,
I have insstructions which say not to hold with a spanner at the contacts end so jamming the gears would seem to be the only other option???
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The nut doesn't need to be bar-tight as once nipped up the taper should hold everything together. I agree a sharp tap with a socket usually seats the taper. I would use some sort of sprag on the timing geas rather than holding the contact breaker end as that is feeble and easily damaged as said.
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If the taper is "grabbing" like it should then there should be no need to jam any gears for the tightening, but of you really must then use the time-honoured method of a piece of rag balled into the inward nip of the gears.
I prefer to give the end of the spanner or socket and tommy bar a whack with a dead-blow hammer for the final tightening.
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Thanks all
Will let you know the outcome
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Hi ALl
I would not and do not use anything to wedge the gears
You already said you have a spanner to hold the crank, Uses It!! or top gear and apply the brake
The mag nut does not need a long spanner or socket/ratchet to tighten it
A short ring spanner and hand tight is enough
Degrease the tapers with some brake cleaner or acetone, some sprinkle a tiny amount of chalk dust on the taper
if it tends to slip while tightening
John
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Have you removed the kickstart mechanism entirely though ?
Being able to easily start an old single is a good yardstick of testing if its in good tune.
Leccy starters often hide such details.
The ole pencil-down-the-plughole is also a simple yardstick of finding where the ignition timing is at,
and finding the tdc mark should likewise not be too difficult.
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We still have the kickstart and it does function. Will give it a kick when we get it timed properly
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Right !
So found TDC and marked it on the sprag wheel with a scribed line and pops .
Then did likewise for 7/16" before TDC and did likewise (See pic 1)
Then timed it as per instructions above at 7/16 before and checked on a couple of forward rotations before locking it up . Then fitted a brand new plug , and started it , (did not start easily) but got it running at a fastish idle, and checked with a timing light.
Quite happy that it is near as dammit . See pic 2 showing the TDC mark under the strobe at ful retard.
Advancing the lever brings the 7/16 mark onto the reference with a strobe reading of about 35 degrees advance and the idle picks up (sorry but I did not have a tacho with me )
All then sounds pretty reasonable until you try to reduce choke and all the popping spluttering and backfiring starts again. Will not run at all without full choke.
Does this whether you have the old carb on , or the new one which was supplied by "draganfly" and said to be set up for this bike. of course we have adjusted slow running and idle screws and checked that needle is in the same (mid) groove in each case.
See pic 3 . Bike has run happily for months on the old one until it started to play up. New one is no better.
Of course carburation is now the suspect but I am not sure :(
Any other suggestions please? Can valve timing be known to move on these.
What else could it be ?
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Full retard has no role in the timing process. In fact, on some bikes full retard is ATDC. It's the fully advanced figure you need to concentrate on here.
I don't get the bit about marks and pops on the sprag wheel. I prefer the time-honoured method of a pencil/lolly stick/cocktail stick down the plug 'ole, then there's no need to account for lash etc.
If there was a fault with the carb(s) like a blocked pilot jet, then no amount of timing resets etc would cure it, but it seems a bit coincidental that both carbs show the same symptoms.
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Hi All,
Can valve timing be known to move on these.
Not unless something jammed the timing gears and sheared the key in the crank pinion
Remove the tappet cover, wind the engine to TDC, if both tappets are free (the pushrods should be free to rotate at TDC on compression stroke) then turn the crank one more complete turn
As the piston rocks over TDC you should be able to see the exhaust tappet dropping and inlet rising this should happen equal amounts either side of TDC
I now see you have a a concentric, The pilot passage bush within the body gets blocked, a 16 thou guitar string or a no. 78 drill can be used to poke through the pressed in pilot bush
It has happened that new concentrics are not set up properly or have swarf and so on inside
John
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Few engines even fully retarded would get right back to a tdc spark, the range of movement is usually limited to prevent that.
And as mentioned previously, many magdynos won't even spark if fully retarded.
If the engine will run with lots of choke on, then mechanically there can't be too much wrong with it. ?
Its either got a massive air leak, or perhaps the ignition source got shoogled up and isn't in the best of health.
Or the jetting for these concentrics is way out, but somehow it contrived to run earlier ??
Note that there have been reports of new concentrics where the drillings weren't entirely completed,
or had swarf in the passageways - so a new carb isn't entirely above suspicion ?
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I see your point about full retard Rex but similarly I am presuming that full advance only comes into play once you get motoring.
We timed it in the "time honoured fashion" with bamboo coffee stirrer and turned a couple of revs to ensure we had consistencey at the 7/16" point before starting.
Only used the timing light and pop marks so we could observe that mothing was really changing on fire up, and we see the advance lever alter the timing from around TDC at full retard, to the 7/16" BTDC at full advance, so timing would seem to be spot on.
As you say, carburation is maybe unlikely to be suspect when a proven carburettor exhibits the same symptoms as a new one.
So what else could be affecting this ? Is there anything in the gear train which can go wrong which might (for example) knock valve timing out of kilter ? We havent yet looked at the cam gears but maybe have to go there next . Would help though if we could find out if there are any known problems in this area.
We intend to look at Valve timing next Chaterlea. I understand the crankshaft gear is on a woodruff key so will look at that first then follow your instructions on the valve positions . The new concentric now has a removable pilot jet which we have checked and seems clean.
The fact that both behave in the same manner seems more than a coincidence . Would a duff pilot jet cause the bike to splutter and die with a small reduction from full choke?
We are not aware that gears ever jammed and from first sight there is no sign of damage . but will look further
R, The AR lever shifts the cam plate quite a long way, so I was not surprised to see full retard taking it back to TDC. Full advance speeds the engine up quite a lot on full choke but only brings firing point to our 7/16" mark and no further so we dont think timing is moving as we start to run. Bike got quite well warmed up but reducing choke even a little caused spluttering and dieing so well puzzled really. Seems to run best at about 1/3 advance but still dies if choke is reduced
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If you give it a big handfull of throttle while reducing the choke, what happens. ?
Even if the idle circuitry is all blocked up, and it runs happily on a big handfull, its a blocked up
carb on the low speed side of things (VERY common in amals left unused for a good while)
It sounds like the mixture is woefully weak - or there is a massive air leak someplace.
Broken valve spring(s) can produce the same symptoms - but with double (or triple ?) springs,
shouldn't be so drastic. Cracked cylinderhead is also possible = big air leak - seems unlikely in
combination with the magdyno coming loose.
You still haven't said ? if its got a magdyno (or electronic ignition ?), but ailing ignition where the
plug can't deal with sparking under pressure isn't unknown.
Magneto can do this to you, but they generally fail slowly and give you a bit of warning.
Dirty points in a magdyno also will do this, you inspected/cleaned the points lately ?
Its there someplace, you just need to find it.
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Sorry I missed the question but it is Magdyno . Points have been throughly cleaned and adjusted (0.012")
Had been running regularly and sweetly for months( rather than left unused) and just suddenly went pear shaped on a short local run at which point it was noticed that the Dynamo was loose. Spark seems strong but cant tell what is going on when it is in the cylinder. Have tried several plugs two of which were new . If spark was week would the strobe operate reliably?
I Dont think that increasing revs improves the situation regarding the choke . We dont rev the guts out of this old lady. it seldom excedds 45 mph on a run , Maybe 50 downhill but will try the process just to eliminate that possibility.
Will start looking closely this week for air leaks, valve timing ptoblems , etc
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Hi Again,
Try squiring some petrol with a spray bottle into the intake with the engine running as you open the throttle
If the engine revs up as you do this then its a carb problem
A quick check of the valve springs can be done by levering up the tappets through the inspection cover
Both should have equal pressure
A sticky inlet valve is another possibility
I had an A10 in for repair that showed great compression but would only run on one cylinder when started
one cylinder's inlet valve springs were soft as putty ::)
John
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Supressed ignition componenets?.....a mag should have a copper wire cored spark lead,the plug and/or plug cap must not be supressed,or the mag windings will break down from overvoltage..................I would also point out the well known fact that its virtually impossible to accurately locate TDC,with stick in plughole,and hard enough with a dial gauge .......therefore ,the full advance point is used as a reference.
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True, but then we're talking about a mass-produced rudimentary iron-head commuter than was designed 70 or so years ago. So many manufacturing variables and so many rebuild variables since that that the figure is only ever a guide or starting point.
The point is that accidentally moving the mag lever too far would make it too advanced, and that's harmful.
I have read on the Net about riders who claim to time to TDC and then jigger with the lever constantly to keep it in the advanced "sweet spot", but I don't think I've ever met someone who advocates that on an old British work-a-day bike.
Dial gauge? A little OTT on a manual mag-equipped B31. This ain't a GP racer... ;)
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Supressed ignition componenets?.....a mag should have a copper wire cored spark lead,the plug and/or plug cap must not be supressed,or the mag windings will break down from overvoltage..................I would also point out the well known fact that its virtually impossible to accurately locate TDC,with stick in plughole,and hard enough with a dial gauge .......therefore ,the full advance point is used as a reference.
There is a suppressor cap so will remove that to eliminate. Not sure what core the lead has but will check , cant imagine that it wont be copper. As you say TDC is hard to find accurately so the logic in using 7/16" figure is easy to accept .
I fully concur with what you have to say too Rex Even if you are a bit out on timing then the lever gives you about 35 degrees of "adjustment" but using that adjustment does not seem to improve the problem, and as you say it is an old iron work a day bike .
Will check through the valve gear again for any mishap and maybe see where tappet clearances disappear ( relative to tdc ) check for soft springs, and see that the crankshaft pinion woodruff key is in good order and not allowing any movement .
We dont have a lot of experience with old bikes, but I was pretty adept with british car engines in the sixties so just have to dig in the annals for the skills, but have to say that this is being a bit of a trial :(
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Just as a follow up:-
HT lead is copper but did not have non suppressor cap so will get one and replace .
Checked drive to valve gear and all sound. Keyway good and timing marks allign so valve timing ok , clearances fine at 0.003". No noticeably soft springs so not much further on really.
Did find a misdemeanor on the carb we removed . Fuel in the float so bouyancy reduced , but not flooding so I presume still holding level OK . But as I said before , new carb behaves just the same .
Not quite sure where to go next.
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If the float has fuel in it, then the fuel level will be higher than it should be, and the mixture will be richer than it should be.
Not sure how that sits with not being able to run without the choke on.
Does it (exhaust) smell noticeably of petrol ?
Did you try someones suggestion of spraying a bit of petrol down its throat while reducing the applied choke. ?
(watch that it doesn't flash back while doing this, so keep an extinguisher or garden hose handy - and be outside)
Not quite sure where to go next.
Magneto.
You can work the advance/retard lever back and forward, and hear the difference ??
It revs up a bit when you advance it ?
You can pull the decompress lever, and it kills the engine ?
If the spark isn't strong enough to spark under compression, then that may be your trouble.
If you had a spare maggie on the shelf, now would be a good time to test it !
Know anyone you can borrow one from ?
When you examined the carb, the needle was lifting up with the slide, all the jets were screwed into place
and the choke slide was lifting up clear out of the way ??
Its in there somewhere, and it should be fairly obvious with such blatant symptoms...
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A sticking valve does sound like a possibility. You usually get increased tappet noise when that happens.
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""If the float has fuel in it, then the fuel level will be higher than it should be, and the mixture will be richer than it should be.
Not sure how that sits with not being able to run without the choke on.
Does it (exhaust) smell noticeably of petrol ?
Did you try someones suggestion of spraying a bit of petrol down its throat while reducing the applied choke. ?
(watch that it doesn't flash back while doing this, so keep an extinguisher or garden hose handy - and be outside)
I thought that but the carb is not flooding so I am presuming ther is enough bouyancy to close the needle valve . We will change the float though
Magneto.
You can work the advance/retard lever back and forward, and hear the difference ??
It revs up a bit when you advance it ?
You can pull the decompress lever, and it kills the engine ?
yes yes and yes
If the spark isn't strong enough to spark under compression, then that may be your trouble.
If you had a spare maggie on the shelf, now would be a good time to test it !
Know anyone you can borrow one from ?
there is a growing wealth of opinion on this being the main suspect . We have a recond mag on an ariel red hunter but it is MO1 (rather than MO1L) Not sure id this would fit. Dont seem to have a local lending library for mags ;) and they seem to be as rare as RHS.
One guy wondered abour electronic conversion so am exploring, but gona try to find a safe way of testing spark strength without the jolt up the arm which I dont enjoy.
When you examined the carb, the needle was lifting up with the slide, all the jets were screwed into place
and the choke slide was lifting up clear out of the way ??
All working as they should , needle in mid groove , new carb has a removable pilot jet which appears to be adjustable but no info or guidanceIt is a Wassel 928 similar to this one . https://www.ebay.co.uk/itm/113753033071
Its in there somewhere, and it should be fairly obvious with such blatant symptoms...""
We must be getting close
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Unfortunately,no other mag will "fit" a BSA ,due to the unique base location setup.... the Ariel mag has the standard" Bosch " four bolt mounting......There used to be lots of WW2 surplus NOS BSA M20 mags around,cant imagine they ve all been used up.
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Looks like the going rate is about £300-400 and in some cases condition is in doubt so looks like a minefield.
If we dont seem to be getting a decent and consistent spark out of this one we may send it to the refurb shop.
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Hi All,
Unfortunately,no other mag will "fit" a BSA ,due to the unique base location setup.
A small amount of work will make it fit
Make some short dowels with 3/8 Whit threads and the other end turned down to the BSA dowel size, (5/16in from memory) screw them into the mag base to replicate the BSA dowels
John
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Doesn't the magdyno on BSAs have the 4 pegs to locate it, and the strap clamps it down.
https://i.ebayimg.com/images/g/PCwAAOSwdIZdrrhu/s-l1600.jpg
BSA's were numerous enough that this doesn't exactly make them rare.
Enfields used the same locating/clamping system ?
Always watch the rotation direction....
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If we dont seem to be getting a decent and consistent spark out of this one
That can be very difficult to judge - apart from taking it for a run, and seeing how it performs.
Yours doesn't currently seem to be doing too good.
(Difficult hot starting is often the 1st sign of trouble, condensor wise)
If you don't know the history of this maggie, that may be a wise move anyway.
Reliable motoring starts with reliable ignition....
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Where I worked as a kid,the old foreman had a simple way of checking timing and spark........remove plug,hold in your hand,place thumb over plug hole,kick motor over.......you can judge ignition timing ,spark,and compression by the bite at the same time as your thumb blows off the plughole.
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I thought the Lucas MO1 series of mags were all essentially the same. If the DoR and spindle height is compatible then you should be good to go.
I wouldn't jump too soon on the mag conversion though...snap diagnostic "repair by replacement" can be expensive and futile.
What was the starting and running like before all this started? For a mag to fail electrically at the same moment that the sprocket came loose stretches coincidence a bit..
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Prior to adding our electric start, the bike could be a pig to start hot, which was awfully inconvenient if it stalled at a junction. Electric start overcame this but I can see how it might mask a basic problem.
Are we saying that the addition of some screwed dowels into the base of our Ariel Mag might make it fit ? Nice if it would as that would be a relatively low cost way for us to prove the mag..
Not much chance of taking this bike for a run untill we can get it to run better though.
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Hi John1168,
Are we saying that the addition of some screwed dowels into the base of our Ariel Mag might make it fit ?
Not might it will fit
Some mags I have removed from BSA's had screw in dowels in place, rather than the more common pressed or cast in ones
I have both Ariels and BSA's and worked on more mags and bikes than I care to remember
Ariel's use a third bolt that goes into the fifth hole in the centre of the "four in a square" on more usually found mags
So if fitting a "normal" mag to an Ariel the extra hole will need to be drilled and tapped
John
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mention of difficult hot start....... a sure sign of mag windings breaking down......a mini capacitor(aka Thorspark) will restore spark for a time ,and for the price is worth trying.........You should note that mag repairers specifically state that any supressed components in the ignition void the warranty on rewinds.....because these supressed components double the voltage at the mag coil and cause insulation failure.
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Yes a difficult hot start is a sure sign of an ailing condensor, and now it sounds like something has further gone bad.
A refurbed maggie will likely make it a one kick starter, hot or cold, no need even for the leccy boot.
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mention of difficult hot start....... a sure sign of mag windings breaking down......a mini capacitor(aka Thorspark)
Do you mean Easy-Cap? Thorspark is the replacement points assembly system.
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https://youtu.be/bUXfzANRKdU
This is a video of a test on the bikes mag, taken off and driven by an electric drill. Spark is jumping a gap of about 12mm
Then we tried a spare mag which was on the shelf and it was difficult to judge but maybe that one seems marginally better , so we have made the dowels for it and hopefully on monday will be in the position to give it a go.
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Spark is jumping a gap of about 12mm
That doesn't sound all that faulty !
This will be interesting to hear the result, I thought we had it nailed, for a while.
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Hopefully will get a chance to test the replacement (on the bike ) on Monday afternoon.
Have to say though that I approach each each "test" with increasing trepidation :-[
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I agree, if it will give a decent spark across 1/2" (for our older members!) there can't be much amiss. Is it a nice blue one with an audible crack?
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It is but the spare from the shelf has a fatter spark. so worth a try changingthat.
If it comes down to just a bad suppressor cap, we will sure be kicking ourselves .
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If it comes down to just a bad suppressor cap, we will sure be kicking ourselves .
Make sure that it doesn't have a suppressor cap at all - direct connection (0 ohms) only for magneto ignition.
Leon
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Fitted spare mag with no suppressor and gave it a whirl.
With new carb in place it fired but would not run. Tickled some fuel up and try again , and same , a short burst then petered out.
Switched back to the original carb (albeit with new float) and we got her to keep running and warm up, not bad but not brilliant still pops back in the exhaust when you reduce the throttle , odd spit back at the carb. Takes quite a time before it is hot enough to reduce the choke, and on a short run up the road it seemed to produce a fair bit of blue smoke.
Will try to upload some videos
Not sure where to go next, Just feel we need someone with an experienced ear to have a look at it .
None of you guys anywhere near Cumbria are You??? :)
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The blue smoke could be from doing a lot of non-running.
A few miles under its belt might clear it out, don't do anything rash.
With the old carb it will run, and with the new it will not.
So we are back to the quality/jetting/cleanliness of the carbs again !
Obviously something is not right, seriously not right, with the new carb.
Be interesting to know if it would run OK with the old magneto.
With the amount of work involved, best you keep the current one in service until all the unknowns become good knowns.
It is permissible to set off down the road with the choke partly on.
That way the engine warms up quicker, and you can judge when the choke can be reduced.
And if it baulks give it back some choke, on the move it shouldn't conk out while doing this.
Ain't old bikes fun !
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P.S. What was the source of your new amal.
As mentioned earlier, recent manufacture of new amals has had some initial terrible quality control problems,
including swarf in some of the passages and even some of the drillings not entirely completely drilled.
Needless to say, this did not make for very reliable running !!!, especially in the low engine speed side of things.
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Not Amal but Wassel . Supplied by Draganfly as direct replacement .
I can see your point about the quality control , but it is out if the reckoning now as she is back on her original proven carb.
Had just topped up with fuel when the problem started but at our usual regular station, and have changed fuel a couple of times since.
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I believe that Amal tightened up on it's quality control some years back, and certainly the last two I've bough have been perfect, unlike those bought over ten years ago which were full of swarf.
The irony here is that the Wasell stuff has a bad name now, but in this case that would appear irrelevant.
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Hi All,
Can valve timing be known to move on these.
Not unless something jammed the timing gears and sheared the key in the crank pinion
Remove the tappet cover, wind the engine to TDC, if both tappets are free (the pushrods should be free to rotate at TDC on compression stroke) then turn the crank one more complete turn
As the piston rocks over TDC you should be able to see the exhaust tappet dropping and inlet rising this should happen equal amounts either side of TDC
I now see you have a a concentric, The pilot passage bush within the body gets blocked, a 16 thou guitar string or a no. 78 drill can be used to poke through the pressed in pilot bush
It has happened that new concentrics are not set up properly or have swarf and so on inside
John
Hi all ,
Sorry i have not been back on this but other things (and the weather) have kept us tied up elsewhere and it is not really biking weather anyway.
So runs best on old carb , timing spot on as far as we know , yet still spluttering a bit .
I am trying to understand the pilot jet function in this . As we look at the Amal catalogue it shows a pilot jet which can be varied yet looks to be a screw in item. We dont have that! just a threaded hole in the underside of the body corresponding with a gallery which seems to draw from the bottom of the float chamber. Where do we find the so called pilot bush?
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Hi
Where do we find the so called pilot bush?
Remove the horizontal pilot air adjusting screw. shine a light into the hole and the bush should be visible
0,016in dia hole in it, suitable guitar string or no78 drill on an extension
Carb aerosol cleaner or similar when squirted in there should also escape up the tiny hole on the engine side of the slide
I cannot believe you have been swopping mags and carbs and all the rest without first of all cleaning the Fu**king carb
:o :o
John
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[ As we look at the Amal catalogue it shows a pilot jet which can be varied yet looks to be a screw in item.
I'm confused. The Amal Premier carb has both a fixed size but removable pilot jet (screwed in horizontally into the body) and a mixture adjusting screw. Maybe you're looking at a diagram of this type, though I thought your carb was a Wassell.
According to Hitchcocks it's been common with the new Premier carbs for people to get these two items confused. The pilot jet should remain tight in the body.
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We have been confused too! By the information in the parts books
See https://www.hitchcocksmotorcycles.com/partsbook-pages/3375
Item 20 is clearly a screw fitted into the underside of the carburettor body hence a threaded tapping in the underside .
Carb has been ultasonically cleaned , washed in brake cleaner , blown through with Hi pressure air so no reason to suspect it not clean.
It is not a premier carb.
The wassel carb however does have the premier type adjustable pilot jet but fares no better (worse in fact) hence it was taken off again and the original refitted.
And remember from the start of this thread that the problems started when Dynamo worked loose and we found that the contacts were breaking at about 1.5" Btdc. Is that in itself not sufficient reason to suspect timing over carburation.
And we have studied a number of manuals , none of which tell us that the pilot jet is hidden away behind the pilot air screw.
You guys may well have lots of experience with big old singles which is why we come here for help. We on the other hand are learning still.
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We have been confused too! By the information in the parts books
Item 20 is clearly a screw fitted into the underside of the carburettor body hence a threaded tapping in the underside.
And we have studied a number of manuals , none of which tell us that the pilot jet is hidden away behind the pilot air screw.
Unless it's a 2-stroke or very early 4-stroke Mk1 Concentric then it would normally have the pressed in pilot bush which can be seen when the pilot air screw has been removed (RH image, below and which often becomes blocked see Bushman's link) and NOT the item 20 pilot jet.
http://accessories.hitchcocksmotorcycles.com/Amal-Carburettors/Amal-MK1-Concentric-Hints-and-Tips/How-it-Works-and-Part-Names
"On most 4 stroke models no pilot jet is fitted, but a pilot bush is inserted in the continuation of the pilot air adjusting screw passage."
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter
(http://amalcarb.co.uk/media/wysiwyg/Amal/24-pilot-circuit.jpg)
http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html
It is not a premier carb.
The wassel carb however does have the premier type adjustable pilot jet but fares no better (worse in fact) hence it was taken off again and the original refitted.
The Amal Premier and Wassell Evolution carbs have removable pilot jets in the same position as the pilot bush which can be adjusted by fitting either a larger or smaller jet.
There is no screw adjustment so they should be screwed fully home and the idle mixture adjusted using the pilot air screw.
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Lot of usefull stuff there L.A.B.
Will have a good read tomorrow night
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Just taken the screw out this evening and there is no Brass pilot bush behind it. The paths are all clear to the tiny holes in the the body and also to the hole below the intake aperture . so no crud or obstructions and this carb would seem to be as it was when the bike was bought and bearing in mind it has run perfectly well on this carb for well over a year.
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and this carb would seem to be as it was when the bike was bought and bearing in mind it has run perfectly well on this carb for well over a year.
And it runs perfectly well on it now - not !!!
Can you tickle the float while this is happening, and the low speed running improves.
Could be your fuel flow or float height might need some attention.
As was suggested earlier in this thread, if the low speed running deteriorates,
then the carb needs cleaning cleaning cleaning cleaning cleaning - until it runs well again.
Ask me (and a million+ other owners) how we know this....
Sounds like you have an earlier version of amal, with fixed pilot jet.
I forget the finer details, but you can't really do anything to it,
just clean clean clean everything until its good again...
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Most concentrics have a filter screen on the fuel inlet thingy under the floatbowl,
have you checked that is sparkling clean ?
Have you drained a sample of fuel through the fuel tap into say a glass jar,
and checked that its sparkling clean. Any rust particles or water globules
are a disaster for carby cleanliness, and could well contribute to such problems ...
Some amals have a drain plug under the base of the floatbowl. If you are sure the gasket
is in good condition, you can remove that and examine what comes out for rust or water.
Anything other than sparkling clean fuel is a potential problem...
White corroded crud in particular.
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Carburettor is spotlessly clean, and all the filters including the banjo.. But will go through it all again to satisfy ourselves.
Were there models of this carb specified with no pilot jet at all . And in such a case am I correct in presuming that the mixture screw is the only regulaion for pilot fuel
When the bike started to play up there was no doubt that the timing was seriously over-advanced. (points breaking 1.5 " btdc ) . What if anything might be damaged by this. It is now spot on at 7/16" and can be seen to be with a timing light and we can see the effect of retarding to fire at TDC, but none of these adjustments seem to produce better running.
The carb as far as we can see is as it was when it was running well, yet it is running like a chip machine and no adjustments seem to improve on that.
Tappet clearances are ok and there is no visible damage seen using an endoscope in the cylinder ( although we cant see all corners )
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Has fitting the correct carb. occurred. It S/B a Monobloc. I haven't read the full saga, so excuse me if this has been covered.
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Hi John,
A pilot jet must be fitted either the bush or a screw in one shown in this rebuild guide
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter
John
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There are versions of this carb with a fixed pilot jet (non-removeable).
If you screw the idle adjustment screw in or out, does it change the idle characteristics ?
The idle adjustment screw (pilot air adjustment screw) alters the AIR supply getting drawn into the cylinder at low speeds (rpms).
If you screw it all the way in, it cuts off the air supply - and the engine should falter and die.
If you screw it out too far, it gives too much air, and the engine will start to falter and even die.
Ihis tells you everything is intact and functioning though, and petrol is being metered through the idle circuits.
Perfect idling is somewhere midway between these 2 extremes.
If there is any (white) corrosion in the idle passages anywhere, things can be blocked off.
And this can be hard to detect and even harder to clean out...
A trace of moisture can cause such corrosion.
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So I am now back after having tried what we considered was everything . Cleaned carbs , prodded carbs , blew carbs out with air ( and carb cleaner ). No trace of even a spec of dust in the fuel filters. Spoke to Amal technical (who suggested Mag) .
Checked timing again and again, tried a bit less advance , a bit more advance , simple when you have made a proper tool.
Checked full timing gear train (all fine ).
Tested mags on the bench but then swopped anyway ,
Swopped carbs,
Spoke to couple of local experts. One said the only other thing left to check is the valves . The other said it would definitely be the valves so off off with its head . All fine but ground valves in anyway and reassembled it all .
And all still the same . Starts at first push of the button or kick but wont run without spluttering and flashing back unless on full choke.
So! What have we missed? we ask ourselves.
Could it be fuel ????
Went and got five litres of fresh 95 ron and put it in the tank
Tried again and Voila! Runs like a dream, after a couple of minutes warming we could ease the choke back to wide open and it still ran sweet and revved freely. No flashing back.
So after an hour or two of self flagellation, we came to the conclusion that in future clean new petrol will be step one .
But we have learned quite a lot in the meantime, both from you guys and from practical experience. So thanks to you all :D
Not quite sure how to sum this up really.
Gonna change the carb anyway cos a 928 is not the correct throat for the machine and there is significant wear . Amal say 626 /300 with 210 main jet , .106 needle jet , and 3 1/2" slide .
Any comments please?????
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All I can say is your fuel must go off mighty quick.....I buy 5 gallon drum of petrol for the mower etc when its cheapest ,about once every six months,dont have the lid tight so the drum doesnt bang with temp changes,and Ive never seen the slightest deterioration of the fuel......Mind ,I never buy alcohol fuel,cause the chainsaw specifically warns about it,and in any case alcohol fuel is actually more expensive than straight unleaded......by about 4 c per litre,even tho the pump price is 2c less /l.(less energy content)......I might add .I can clearly smell the alcohol in 10%,and also the exhaust smell of the mower is obvious with alcohol,so there is no chance of having it by mistake......Not that Im doing a lot of mowing with the drought......with bikes ,I always drain and remove the tank if Im not using the bike regularly,and swill out with 2 stroke mix.This stops the rust forming around the inside near the cap.
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We dont have those options at our pumps . The troublesome fuel was just bought at a local station shortly before this thread started . BP ultimate.
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Well I've never had a problem with ordinary unleaded whether with or without ethanol - sometimes left for 6 months and then starts first kick. Maybe I'm just lucky.
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Seems to depend on the engine. My V-twin and lawn mower are both low comp SV's and they need new fuel before they'll start in the Spring. The OHV bikes on the other hand, do fire up on old juice.
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Juice was no more than three months old yet apparently clean , New stuff sorted the bike (and made us look like a pair of Idiots) .
Old juice was yellowish . New stuff virtually clear .
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I once bought a tankfull of fuel for my regular roadbike (at a small servicestation)
and the the performance going up the next hill was so woefull I stopped and checked
my bike was still all present and intact.
I don't know what was in that fuel, but some of it was less than burnable. ?
The next tankfull restored the zip....
Modern fuels seemed geared more towards fuel injection, and are more diesel-like in constituents,
and the more volatile components may be less in evidence - which will affect carbureted engines ?
Fuels apparently are also made to summer and winter formulas, so out-of-season fuel performance
may be less than ideal perhaps.
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There was a chain of cut price fuel outlets here that were notorious for fuel problems and engine damage........run by gentlemen of middle eastern appearance--as the cops say--anyhoo,eventually fined $8 million by the consumer protection for selling recycled paint thinner as fuel,and still on the Customs & Excise wanted list for non payment of fuel excise. ----the proprietor has decided to return to Iran.....Despite the recycled thinner fuel being common knowlege ,it took the feds several years to act.....and in typical government fashion they just stuck fuel excise on all paint thinners...problem solved.
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The problem fuel came from a local station , one of a chain , run by a local cumbrian family and all of their stations sell BP product.
I believe the original problem stuff was their BP "ultimate " whereas the bike is now running fine on 95 Ron regular fuel .
My last runabout was a BMW K100 but I was told by the guy who sold it to me that he found it did not run well on ultimate fuel, and to ensure I used regular .
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There's a seller of "Stay-Up" floats for Indians etc in the US, and he monitors fuel quality on a regular basis simply by soaking his floats in fuel for a month or so and monitoring the varying reactions.
His findings seem to match the post above in that he believes industrial solvents are being "disposed of" via the petrol supply chain. Modern vehicles aren't unduly affected due to engine management systems, but our old clunkers can be.
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Interesting
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On the other hand,I use unleaded as thinner for spraying red oxide......any alcohol ,and the paint curdles and blocks the gun.....Fraction of the price of paint shop supplied thinner...