classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: Rockburner on April 11, 2023, 12:27:31 PM
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I've inherited my father's JAP engined, Featherbed framed 'special', and I'm trying to get it setup for road-riding, it's registered and has been used in the past for road-riding and display events (eg Kop Hill), but since he died in 2021, it hasn't been used (in fact it wasn't used much before then), and I'm struggling to get it running right.
The engine is a a ~400cc* JAP 4-stud motor, with a Cooper ally small fin barrel (ie, from a Cooper race car), running an AMAL Monobloc, and a BTH Magneto.
Frame is a Slimline Norton Featherbed.
Gearbox is a 1950s Norton 4-speed.
Akront wheels, brakes are Grimeca 4-ls front, Norton rear.
So far I've got it 'running' after cleaning out the Monobloc carb and reassembling.
It starts easily and fires up fine - in the workshop**. Previous to cleaning up the carb it wouldn't tick over, now it ticks over fine and responds to revving fine when on the stands.
However - I've taken it out on the road (round the block) a couple of times, and it always does the same thing: It'll run fine for a couple of minutes - up through the gears to about 60mph or so, a couple of times, but then, within 5 minutes of starting, the power just dies away completely and it'll barely run, although it does seem to be able to tickover still.
I thought it might be running rich, so I lowered the needle in the carb (to the lowest option, from the 2nd lowest option), and that didn't seem to make much difference - although it did seem a little 'weak' at full throttle - so I'm slightly concerned I've gone too far the other way and made it lean, OR the problem is something else completely. It goes to full throttle very easily: fitted witha Tomaselli Quick Action twist-grip - only about 1/4 turn from closed to WOT.
The first time I took it out, and it started playing up, the plug came out very black and oily (but dry).
Then I checked it two days later prior to my second test-run, and the plug was actually wet with oil.
After the 2nd test-run, the plug was again black and oily, but dry (ie not sooty black, but oily black).
The engine is also pushing about twice as much oil to the head as it should - I've read (somewhere) that the Pilgrim pump should be pushing oil to the head at a rate of 1 drop every 5 seconds at tickover. Currently it's running about 2 drops every 5 seconds, so I'm going to adjust that, but before I do - would running R30 instead of R40 be the cause of a doubling in the oil feed rate? IIRC Dad ran it on R40, but I was adviced that R30 might be better during the cooler days at present (and switch to R40 during high summer or for faster riding).
The worry I now have is that oil seemed to be getting into the combustion chamber - would that indicate a leak from a valve-stem? I'm not even sure if these motors run valve-stem-seals (in the modern sense), or could it just be the 'over-oilling' overwhelming the valve-stem?
Very grateful for any advice that anyone can give!
(https://live.staticflickr.com/65535/52801072462_8604e158db_z.jpg)
* It's a mix of 500 and 350 parts which come out at around 400cc.
** Starts fine sitting on a paddock stand.... pull the bike out into the fresh air and it takes 10-15 kicks.... could this be due to the fact that I'm starting it on an angle? on the paddock stand it's pointing slightly 'downwards' (rear wheel is raised a couple of inches), but outside the uneven ground means it's leaning 'backwards' slightly (pointing 'upwards', rear wheel is a couple of inches below front) ???
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I've found monoblocks can cause difficult starting when on side stand. One of my bikes is a pig on the side stand but stand it upright and it's fine. Isn't that one of the reasons Amal went to the concentric carb ?
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That it runs fine when it goes vindicates the carb set up. That it plays up hot suggests the magneto. An open circuit within the mag windings arcs to form a carbon track. This is of low resistance when cold, but high resistance once it warms up, reducing magneto output.
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Hi
Have you checked the fuel tank vent? / fuel tap flow, it sounds as though it is running out of fuel after 5 min but still enough flows to keep it ticking over ?
John
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That it runs fine when it goes vindicates the carb set up. That it plays up hot suggests the magneto. An open circuit within the mag windings arcs to form a carbon track. This is of low resistance when cold, but high resistance once it warms up, reducing magneto output.
Hmm - yes - that could be the issue, I've seen it before (we had a Comet that would do that - it would run fine when running, but if it stalled then you had to wait for it to cool down before it would fire again! Very annoying if you stalled it on a long rideout!).
What's the best way to test this??
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Hi
Have you checked the fuel tank vent? / fuel tap flow, it sounds as though it is running out of fuel after 5 min but still enough flows to keep it ticking over ?
John
Good thought - I'll check that as well.
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I've found monoblocks can cause difficult starting when on side stand. One of my bikes is a pig on the side stand but stand it upright and it's fine. Isn't that one of the reasons Amal went to the concentric carb ?
Just on this point - when kicking the bike outside, it was upright, not on the side-stand, although I suppose it be leaning slightly when I kick, but not much.
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What's the best way to test this??
Take it on a long rideout - and see if it will restart hot !
I'm going to add that this often indicates a problem with the condensor.
Buried within the armature windings, on many magneto types.
Starts easily when cold, difficult or utterly refuses to start when hot.
The opposite with bad or failing wiring really.
Some such ailments can be cured with those little Brightspark Easycaps,
as a condensor replacement. For some magneto types.
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If you look at a monobloc - or the earlier 276 type - you'll see why starting on the prop stand can be problematic. The level of petrol seen at the jets will drop as the float chamber is on the left of the carb thus weakening the mixture.
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What's the best way to test this??
Take it on a long rideout - and see if it will restart hot !
i would if it ran for more than 3 minutes!
I'm going to add that this often indicates a problem with the condensor.
Buried within the armature windings, on many magneto types.
Starts easily when cold, difficult or utterly refuses to start when hot.
The opposite with bad or failing wiring really.
Some such ailments can be cured with those little Brightspark Easycaps,
as a condensor replacement. For some magneto types.
I'm looking into people for that now
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In the same vein as blocked petrol tank breather, it's worth checking that you still have tappet clearance as the motor warms up.
Leon
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Are you sure the carb isnt worn out........I had similar trouble with an Ariel,the monobloc had been fitted new,but the slide was completely worn out ,as was the slide bore.......monoblocs had a bad name for being rubbish alloy,but then so did concentrics.
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Hi
Have you checked the fuel tank vent? / fuel tap flow, it sounds as though it is running out of fuel after 5 min but still enough flows to keep it ticking over ?
John
Fuel flow looks ok to me:
https://youtu.be/7I_E-CXGeMY
And now I need more fibre washers: the brand new one from Burlen has gone hard already and won't seal. Might try making one out of Viton....
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Hi,
I would run the flow test for at least 5 min or as long time wise to simulate when the trouble happens ??
John
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Hi,
I would run the flow test for at least 5 min or as long time wise to simulate when the trouble happens ??
John
I've got to replace the seal anyway so I'll have another go.
But pretty sure it's fine.
The filler cap is Monza type and i stripped it to check the breather bikes and they were fine.
I'm going to get the Mag rewound so will be stripping the bike down. But irritating as i was hoping to be riding it this summer.
Dies anyone have a link that explains how to setup timing and contacts for someone who's never seen a cintact breaker before? I've never done it and never seen it done. :(
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Try this http://classicmotorcycleforum.com/index.php?topic=6299.msg31348#msg31348
It didn't work for the person who needed it...
Leon
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A failing mag coil needs to get hot before causing problems.......typically this takes 1/2 hour running.............while one of the film capacitors (and remagnetizing) will improve a failing mag,it will also accelerate its demise with the higher voltage in the coil.
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A failing mag coil needs to get hot before causing problems.......typically this takes 1/2 hour running.............while one of the film capacitors (and remagnetizing) will improve a failing mag,it will also accelerate its demise with the higher voltage in the coil.
It's a fair point. Can you suggest any other cause for the bike dying after 5 minutes? I'm pretty sure it's not fuel flow, but will be checking that again.
What other causes might there be for a JAP engine to die after 5 minutes of running?
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Some things are easy to check. Just lift the fuel cap after a few minutes and you'll know it's not that. Check the tappet clearance when the bike stops - you need some. Check that the valves aren't tightening in the guides at things warm up, and so not closing properly - check that there is some compression immediately the bike stops. Beyond that, maybe the magneto is tired.
Leon
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Checked the fuel flow again last night, it's fine.
Also pulled the rocker cover off and rotated the engine using the kickstart (not ideal), but with that cursory inspection, it looks like the inlet valve has closed up completely.
Hopefully it's just the gap closed up and it's not a case of getting the valve seats redone. I think the head has already had phosphor-bronze seats put in, but not sure.
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From what you say it hasn't run much so I doubt whether valve seat recession is the problem. Either the clearance was incorrect from the start or has somehow tightened up - although they usually slacken rather than tighten. Are you sure you're checking at the right point?
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From what you say it hasn't run much so I doubt whether valve seat recession is the problem. Either the clearance was incorrect from the start or has somehow tightened up - although they usually slacken rather than tighten. Are you sure you're checking at the right point?
Not yet!
Need to get the chain case off to rotate the engine properly, and then expose the valves fully to see what's going on
I also need to find a clearance measurement.
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Need to get the chain case off to rotate the engine properly, and then expose the valves fully to see what's going on
Just remove the spark plug, put it in gear and either rotate the back wheel or wheel it
along the floor to get the engine to where the valves are closed.
You'd probably want to be seeing 5 or 6 thou.
But don't quote me on that, or hold me to it.
I haven't seen your engine...
Much less than that is likely to be a problem though.
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If you do as suggested by R and use a pencil or such through the plug hole you'll find that there are 2 top dead centres. One of these should have a clearance on both valves (the end of the compression stroke), the other should have no clearance (end of the exhaust stroke). Make sure you're checking on the right one.
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If you do as suggested by R and use a pencil or such through the plug hole you'll find that there are 2 top dead centres. One of these should have a clearance on both valves (the end of the compression stroke), the other should have no clearance (end of the exhaust stroke). Make sure you're checking on the right one.
Yes - I know how to do valve clearances, ;) (been doing them on my 1150 BMW for 20 years)
I just didn't know 'where' on the JAP engine the clearance was measured, or what the clearances should be. I also don't know if there's paper gaskets that need to be bought first before I dive in.
Luckily I've got a copy of "The Book of the JAP Engine", and I've now found the info I need. Apparantly the clearances are 0.002" when cold, measured directly between the tappet and the valve-stem.
Which is what I expected, kinda, but I was confused by the multiple covers over the valve-gear: it would have made sense to me if the measurement was made somewhere in the rocker box because then it's 1 cover to remove and reseal, rather than 3 (or more).
I'm also slightly concerned about re-sealing the covers, the rocker cover contains 2 'bosses', which act on the rocker end-faces to maintain the 'end-float'. So adding a gasket of some sort would affect that end-float. (the rocker cover plate is also cracked, which doesn't make me happy either!)
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It's one thing that a particular JAP engine needed 2 thou of tappet clearance, another to know what is required in a hybrid engine made from an unknown collection of bits half a century on. Who knows what the push rods are made of? The key thing relevant to your problem is that there is some valve clearance when the engine stops running. When the engine stops stand on the kick start lever and see if the compression is still there.
Leon
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It's one thing that a particular JAP engine needed 2 thou of tappet clearance, another to know what is required in a hybrid engine made from an unknown collection of bits half a century on. Who knows what the push rods are made of? The key thing relevant to your problem is that there is some valve clearance when the engine stops running. When the engine stops stand on the kick start lever and see if the compression is still there.
Leon
There's definitely compression. If anything I think the exhaust valve clearance has come loose. There was a lot more movement on it when I made my cursory check than there was on the inlet.
You're right of course that it's a 'made-up' engine, but I've found some notations made in my father's inimical manner within the books that make me pretty confident that this was what he understood to be 'right' for the engine.
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If its a cast iron engine,then inlet just free and exhaust at 002 will be correct...........I wouldnt assume anything drastic has happened ,but concentrate on the faults likely to develop with out of use .......Fuel and magneto.......The symptoms sound like fuel ........check the monobloc float valve ....there is a small spacer on the float spindle sometimes left out.....or maybe the needle valve is blocking fuel flow ........this was a fault with the nylon ones ..........if thats OK for sure ....then Id take off the mag chain,spin it and see if it has a fat blue spark.........any trace of red spark will be condenser problem from moisture pickup.
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If its a cast iron engine,then inlet just free and exhaust at 002 will be correct...........I wouldnt assume anything drastic has happened ,but concentrate on the faults likely to develop with out of use .......Fuel and magneto.......The symptoms sound like fuel ........check the monobloc float valve ....there is a small spacer on the float spindle sometimes left out.....or maybe the needle valve is blocking fuel flow ........this was a fault with the nylon ones ..........if thats OK for sure ....then Id take off the mag chain,spin it and see if it has a fat blue spark.........any trace of red spark will be condenser problem from moisture pickup.
To the best of my knowledge, the engine is predominantly standard JAP parts, apart from the alloy barrel (as used in Cooper race-cars).
I've done everything I can with the carb, it flows fuel fine, but might be jetted or set slightly off - I'm not sure how to check it further because I can't currently run the engine for more than 5 minutes (ie to get it hot), because it loses all power and will barely run at that point. Hence moving on to things like valves and timings.
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May we enquire what spark plug it currently has in it ?
(you have tried a NEW plug, haven't you ?)
The wrong heat range may see the plug overheat OR be too cold to keep running,
even in those few minutes.
A bit unlikely, given how general purpose plug types of old were, but you don't know until you try it ...
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Hi R,
There is no need to pull off all the valve covers to check the tappets
Just make sure there is a little movement at the pushrod adjusters, pushrod free to rotate and a smidgin more on the exhaust side.
No gasket needed on the inspection cover, a light smear of Hylomar if you must
John
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Not my bike John !
My JAP is of the sidevalve persuasion.
You can SEE the valve clearances !
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May we enquire what spark plug it currently has in it ?
(you have tried a NEW plug, haven't you ?)
The wrong heat range may see the plug overheat OR be too cold to keep running,
even in those few minutes.
A bit unlikely, given how general purpose plug types of old were, but you don't know until you try it ...
It's a Champion L86C. From I've found to read online about the plug itself, it seems about right.
But a new one is a good idea. I meant to order one a week or so ago and forgot, Thanks for the reminder!
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Hi,
Sorry R I was abbreviating Rockburner ::)
John
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Heyhey, I resemble that remark .........
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Hi,
Sorry R I was abbreviating Rockburner ::)
John
I've been called worse..... :D
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What sort of compression should i be getting?
I realise that it's a hard question to answer given that the engine is a bitsa with 350 and 500 internals rounding out to about 400cc, but any educated guesses would be appreciated.
Currently getting about 75psi.
https://flic.kr/p/2ozWQPH
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Compressions are ALWAYS tested hot, with the throttle wide open.
Otherwise the results are a little haphazard.
Any idea/inkling of the compression ratio ?
75psi seems a little low - for a healthy ohv hotrod. ?
Tipping a teaspoonful of oil down the plughole, kicking over a few times and retesting is advised.
If the number jumps upwards, then the ring seal is not so good.
Either new rings or more running in is required.
Or testing hot, with that throttle wide open ...
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So, some health issues have kept me out of the garage recently, but recovery is under way.
I've checked the valve clearances and they seem to be ok, ie there is play at tdc on both rockers when cold!
I've ultrasonicly cleaned the Monobloc and reassembled it with the upgraded Viton tipped float needle and the rest of the refurb kit from Burlen.
I stuck some petrol in the tank and opened the taps.
No leaks was the first win!
I tickled it up but instead of fuel coming out of the tickler, it eventually started dribbling from the manifold, bit odd, but the fuel is flowing.
Kicked it a few times and eventually it fired up, bit rough at tickover, but some small adjustments fixed that.
Opening the throttle though and there's a lot of spitting and backfiring, flames from the open bell mouth. Not good. I'm now worried that the inlet valve isn't shutting correctly, with the throttle fully open you can look down the manifold and see the flame front!
Nevertheless I took some time to adjust the oil feed to the head which wasn't running, now running at (roughly) a drop every 5 seconds on tickover, just like the book says.
I'm going to try a smaller main jet in case it's just a case of over-fuelling, but if it's still backfiring I'm going to have to have another look at the valves.
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The main jet doesn't come into play until the throttle is more than about 3/4 open,
so you can probably omit that step.
Dropping the needle a notch would achieve less fuelling, at lower engine speeds.
It does sound more like cam timing though.
Unless the inlet valve isn't seating too well ??
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I have never understood why the Amal tuning procedure starts with the main jet, which as you say isn't used until wide open throttle. I always start with a main jet I know to be too big and go through the process of setting up idle mixture screw, cutaway and needle in that order before even considering main jet.
People wlays talk about increasing main jet size when they fit a less restrictive exhaust system but unless they go everywhere with the twistgrip on the stop - and by the sound of it many do round here - that seems a bit pointless to me.
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The main jet doesn't come into play until the throttle is more than about 3/4 open,
so you can probably omit that step.
Dropping the needle a notch would achieve less fuelling, at lower engine speeds.
It does sound more like cam timing though.
Unless the inlet valve isn't seating too well ??
Good point about the needle - I"ll try that (not sure what it's on at the moment tbh)
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It appears to be a race bike ,so its going to have a pretty radical cam in it..........this may make it hard to check the valve timing ..........and spitting back at slow revs may be a side effect of very early inlet opening.
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It appears to be a race bike ,so its going to have a pretty radical cam in it..........this may make it hard to check the valve timing ..........and spitting back at slow revs may be a side effect of very early inlet opening.
Its a fair point, I've no idea what cam is in there. Just looking in the cam bix is an engineer out of the frame job (i think), and knowing my Dad, it may well have a "hot" cam.
What can be done to alleviate that situation?
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What kind of motor is it..........I assume its a 4B or similar .....in which case someone like Cameron Engineering will be able to supply a milder cam......at a price,mind you.
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What carb is it ......the pic seems to indicate a Type 27 speedway carb ,or maybe a 10TT
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What kind of motor is it..........I assume its a 4B or similar .....in which case someone like Cameron Engineering will be able to supply a milder cam......at a price,mind you.
It's a 4-stud, with a Cooper barrel (lightweight, small fins), and the internals are a mix of 350 and 500 that equate to 400cc (approx). I keep forgetting how Dad actually managed that.
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What carb is it ......the pic seems to indicate a Type 27 speedway carb ,or maybe a 10TT
Amal Monobloc 389.
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I tinkered with the JAPton last night. (Life is busy at the moment, so I don't often get into the workshop).
It's all back together but wasn't running properly - lots of spitting back and backfiring in the exhaust.
Got it running, and spent about an hour going back and forth between the ancient Monobloc "Notes" leaflet (Dad had some photocopies so at least I wasn't getting the original filthy!)* Eventually got my head around it and realised that the damn thing was running "weak" in the mid-range and so pulled the needle up a notch (the first thing I'd done was lower it a notch to the "top" notch, it refused to run on that setting). Now it's in the middle of the needle's range its actually running pretty well (once it's hot). The occasional spit back or backfire, but I think I can live with that for now.
Happy bunny!
During the course of the session I'd spotted a couple of nuts that had fallen on the floor - one was an engine bolt that (in hindsight) I know was loose - the primary chase mounting lug is held in place by it and I'd simply forgotten it was loose.
The other was the nut off the forward connection for the gear linkage.... it's a nyloc, but I discovered that Dad had cut the bolt for it down so short that the threads aren't actually engaging the nylon locking collar! ( ffs). Couldn't be arsed at that point to root around for a better bolt so I just pushed the nut on upside down. Hardly ideal but it'll do to hold it all together while I figure out another issue.
I was wiping some oil off the top of the crankcase when I discovered something that terrifies me...
(https://live.staticflickr.com/65535/53099362614_00d00c9d8f_z.jpg)
That bolt, the one between the push-rod tubes, is loose, and it won't go tight. :o
It just revolves.
Now - I may be wrong.... but, to me, that indicates that there's a friggin NUT on the other side of the case, that is loose, and is hanging on the threads of the bolt.
I may be wrong, and the loose bolt is caused by the threads on either the bolt or the casing being thoroughly knackered.
But - either way, the mininum work needed before I can do anything with the bike is to strip the entire right side of the engine away to check what's going on in the timing box. :roll:
I can't take a chance on the probability of a nut dropping into the timing box.
So - The JAPton is unlikely to see tarmac again this side of Easter, simply because I know that I've never done any of this stuff before and I'll be taking things very slow and thoroughly checking it all, and researching how it all works. Oddly, for all the tinkering I've done over the years, this is the first time I've ever had to actually do the timing on anything.
I also seem to have been thrown off / barred from the JAP Engine Facebook group I was on - so also need to find a J.A.P. specialist source of further information.
Dagnabbit.
* I must get a copy of that leaflet blown up and laminated. I did the same with the exploded diagram for the carb and it's an invaluable reference sheet).
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Most likely the thread in the crankcase is stripped. I think it unlikely there's a nut underneath. Getting the head & barrel off will only take half an hour or so.
Re the spitting back - I had a similar problem with my ES2 fitted with a monobloc and found that a richer slide cutaway (lower number) sorted it out, as the cutaway controls the mixture on transition between idle and the point that the needle jet takes over. The slide was kindly donated by someone on here but sadly I can't remember who.
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Most likely the thread in the crankcase is stripped. I think it unlikely there's a nut underneath. Getting the head & barrel off will only take half an hour or so.
Re the spitting back - I had a similar problem with my ES2 fitted with a monobloc and found that a richer slide cutaway (lower number) sorted it out, as the cutaway controls the mixture on transition between idle and the point that the needle jet takes over. The slide was kindly donated by someone on here but sadly I can't remember who.
I "believe" that I need to get into the timing chest, rather than the crank case volume itself - so need to get the timing apparatus off the rhs, rather than the head and barrel off, but need to find some internal schematics first to check that.
It looks to me like the pushrods are actuated by the cam-followers in a side-chest.
(https://live.staticflickr.com/65535/53099753484_77ea83342b_z.jpg)
Would be seriously useful to have a 2nd engine to play with and see where everything goes!
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Yes, it's just like 99% of old motorcycle engines.
I don't know what the problem bolt does: I assume that holding the head and cylinder down is left to the four main studs, which are suitably symmetric, in which case is the problem bolt just filling a hole used for an oil inlet or breather? If it turns, what happens if you turn it and pull it up? There is no way it has a nut underneath inside the timing chest.
Leon
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I'm with Leon.
Although I no longer have a JAP engine, I'm sure that there is no actual function from a bolt there between the pushrods. I suspect that it is a breather someone has added at some point, and that brass "bolt" is actually a plug. As Leon suggests, try lifting and un-doing it; it will probably screw out to reveal an ill-fitting plug.
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Yeah - that's the first thing I'm going to try when I'm next in the workshop. The engine was very hot when I first observed the issue so I was struggling to get at the thing!
I seriously hope that there isn't a nut underneath it... but knowing my Dad..... there's a possibility....
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oh yeah - there's one other weird thing...happening:
On the Monobloc carb, although I've cleaned it all up, when I use the tickler to push the float down, it "works" - but the fuel doesn't overflow through the ticker - it eventually overflows out of the bellmouth! (or possibly a tiny hole in the inlet manifold).
The tickler is imply a metal tube, closed at the top end, but with a small hole on the side about a mm down from the top. The bottom of the tube is squared off, but not closed up, and it's completely clean - it's not blocked in anyway.
The top of the float - which the tickler pushes down on, is rounded, so there's no "flat plane" on which the end of the tickler could possibly "seal".
So I'm highly confused as to why the fuel isn't exiting out of the tickler!
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Managed to unscrew the bolt this evening.
The threads on both the bolt and the case are "tired". But i found a bolt in my grab bag of Imperial bolts that actually screws in and will go "tight".
https://flic.kr/p/2oUxRsd
https://flic.kr/p/2oUwLGC
Old bolt on left....
So I'm going to cut it a bit shorter (both bolts are twice as long as they need to be), and smother the top end of the threads with silicon and put it in with an ally crush washer (unless i can find a suitable fibre, but i detest fibre washers).
Before that though, I'm going to stuff an endoscope into the hole!
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Ive sort of wanted a copy of "The JAP Engine " by Fenner for years ,but never going to pay a silly price .........then I just happened to see an as new copy with the red dust cover intact for $10 at a flea market .........anyhoo,this book includes a section by Wal Phillips on the speedway engines .........and thats where the photo of the timing gear comes from .
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Ive sort of wanted a copy of "The JAP Engine " by Fenner for years ,but never going to pay a silly price .........then I just happened to see an as new copy with the red dust cover intact for $10 at a flea market .........anyhoo,this book includes a section by Wal Phillips on the speedway engines .........and thats where the photo of the timing gear comes from .
Wow! That's an excellent find!
I have both the Fenner, and 2 copies of the Pitman "The Book of the J.A.P. Engine" (2nd and 3rd editions). My Dad always like to check the definitive sources as much as he could. The problem is that I think a lot of his notations were for his other J.A.P engined bike... a 1930 HRD Vincent, which had an earlier J.A.P. engine in it, than the one in the special I've got.
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last week I "fixed" the hole in the JAPtons crank cases (timing chest actually).
I did stick an endoscope down it, but there wasn't a lot to see!
I cut down the new bolt so that it was roughly the length required to fill the cases, with a crush washer on top:
(https://live.staticflickr.com/65535/53124941883_658a497e38_z.jpg)
Then fitted it in with a good amount of Soudall Fix-All smeared into the threads and around the crushwasher and head. With any luck that will act as a seal and thread-lock even though the bolt isn't done up that tight. I tried very hard NOT to strip the threads so only did it up as tight as I dared....
(https://live.staticflickr.com/65535/53123859002_d901c0f550_z.jpg)
Obviously will be keeping an eye on it, but I can't move it with my fingers... so it's an improvement
I had an idea that the issue with the carb tickler might have been the paper gasket between the jet block and the main body (the surfaces this gasket mates to are not the smoothest....). So I stripped the carb down and put a small amount of blue-hylomar on each face of the gasket and reassembled it.
No difference. Whatever is preventing the tickler working correctly is still evading me. Next attempt will mean going into the float bowl itself and seeing there's something odd about the interface between the tickler and the float. I've been doing some reading up and it seems that the new nylon floats sometimes cause minor problems so it's worth taking a look.
(https://live.staticflickr.com/65535/53125829705_e846708bb1_z.jpg)
Took the JAPton out for a spin round the block this evening.
It might run ok at less than 1/4 throttle, but any more than that and it starts bogging down, won't fire at all, then after 2 or 3 deafening explosions from the exhaust it'll pick up and run well for about 10 seconds before it starts bogging down again.
Rinse and repeat again and again if I try to ride it anything more than 1/4 throttle (ish).
And obviously it's still pissing oil....
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So... Back to to the tuning leaflets....
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I wonder if the bolt should be a breather? Earlier JAPs were very clever in how their engines breathed, and the timing chest was vented directly to the atmosphere. Oil will be forced out randomly if there is no method to relieve excess pressure from the cases/timing chest. I know all about the early engines (where venting the crankcase will cause the entire oiling system to fail), but unfortunately I don't know the details of the later oiling systems, other than to say "be careful of what you vent and what you don't".
Leon
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JAPs traditionally breathe only through the oilbox ......if you put breathers anywhere else ,you upset the lubrication system,and may even cut off the big end feed
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No difference. Whatever is preventing the tickler working correctly is still evading me. Next attempt will mean going into the float bowl itself and seeing there's something odd about the interface between the tickler and the float. I've been doing some reading up and it seems that the new nylon floats sometimes cause minor problems so it's worth taking a look.
I seem to recall that the tickler on Monoblocs can be "adjusted" slightly by tapping the central tube down or up in the carb body. Maybe the current position is too high for juice to appear at the tickler before it drips from the carb itself?
Or maybe I'm thinking of another carb... ???
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JAPs traditionally breathe only through the oilbox ......if you put breathers anywhere else ,you upset the lubrication system,and may even cut off the big end feed
That's pretty much my understanding too.
This bike "has" run well in the past, but was parked up for a few years (my Dad's health deteriorated and he died in '21, it took me a year or two to be ready for looking after the bike).
Last Friday I Took the JAPton out for a spin round the block:
It might run ok at less than 1/4 throttle, but any more than that and it starts bogging down, won't fire at all, then after 2 or 3 deafening explosions from the exhaust it'll pick up and run well for about 10 seconds or so before it starts bogging down again.
Rinse and repeat again and again if I try to ride it anything more than 1/4 throttle (ish).
I've been pouring over the literature I've got (the JAP books, and the AMAL tuning leaflet) and I still can't get my head around whether these symptoms are the carb set too rich, too weak, or something else completely.
The Amal booklet seems to suggest that issues with firing in the exhaust are ignition related.... But that doesn't balance with the fact that the engine WILL run properly for a few seconds before it bogs again, so I'm somewhat confused.
As I say, it'll run ok for a bit, then it seems as if something "builds up" and it stops firing, until the fuel in the exhaust detonates, and it clears up and runs again.... Until the "blockage" builds up again. That's what makes me think it's not ignition or timing - because presumably it wouldn't run at all at lower throttle openings etc if the timing had shifted?
Next thing I'm going to do is go over the inlet manifold and exhaust joins and check there's not gaps or holes in the system.
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Well, I've still not figured out what's wrong with the JAPton. Did some checks last week and fuel flow is good ( more than half a litre per minute, which ought to be fine).
Raised the needle by one because i thought it might be a bit weak, and tried starting it up and although it started easily enough, its still spitting back and backfiring.
I'm beginning to think the ignition timing has slipped, so i took a cover over the magneto drive sprocket to check it.
Seemed fine so went to put the little cover back on, and bugger me if the sodding thread didn't strip.
GAH!
So I'm going to put the JAPton aside for a bit and concentrate on the other projects i need to get done before winter, and will very likely spend the winter stripping the thing down and learning more of its foibles.
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That'll be fun.....
I am considering a Chinese pitbike carb for my Tri-Greeves. I have the correct monobloc but it's missing bits and is in poor shape. For £15 must be worth a punt......
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Have you tried tickling it while its running.
The amal, the amal.
(Not while riding it either.)(could be a risk to life and linb)
If its fuel related, this should tell if its starving for fuel.
There is some chat about viton tipped fuel needles, or not, in monoblocs.
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The obvious answer is to fit another carb that is known to work OK.
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There is some chat about viton tipped fuel needles, or not, in monoblocs.
Yep, some claim that the Viton needles are prone to sticking "up" and shutting the supply of juice off.
Re the pit bike Choagy carbs, an old boy I know paid £14 for one off Ebay, and stuck it on his reluctant Tiger Cub. Apparently it started second kick and even ticks over fresh out the box.
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The obvious answer is to fit another carb that is known to work OK.
Its certainty a thought.
Do you have one to lend? ;)
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There is some chat about viton tipped fuel needles, or not, in monoblocs.
Yep, some claim that the Viton needles are prone to sticking "up" and shutting the supply of juice off.
Re the pit bike Choagy carbs, an old boy I know paid £14 for one off Ebay, and stuck it on his reluctant Tiger Cub. Apparently it started second kick and even ticks over fresh out the box.
I've heard this myself which is why I'm considering it. Ebay also has sets of main & idle jets for a couple of quid or so. I've never had the experience if viton needles sticking despite using them for decades.
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There is some chat about viton tipped fuel needles, or not, in monoblocs.
Yep, some claim that the Viton needles are prone to sticking "up" and shutting the supply of juice off.
Re the pit bike Choagy carbs, an old boy I know paid £14 for one off Ebay, and stuck it on his reluctant Tiger Cub. Apparently it started second kick and even ticks over fresh out the box.
I've heard this myself which is why I'm considering it. Ebay also has sets of main & idle jets for a couple of quid or so. I've never had the experience if viton needles sticking despite using them for decades.
Got any links for the jets?
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https://www.ebay.co.uk/itm/404463872342
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Yes ,im tossing up whether to get a 28mm RE carb ,which will be jetted correctly ,or a cheapy PWK a bit bigger ...maybe 30mm.........from what Im told ,if the cheapy isnt jetted right ...or at all......buying bigger jets is a no go ,and the jets are different thread from mainstream carbs that the Chinese ones are copied from.
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I've bitten the bullet and ordered a 20mm device (equivalent to the standard 3TA monobloc). I'm emboldened by the fact I just bought a complete CDI / coil package for my Honda XBR500 and it seems to work as well as the Dutch one I paid £110 for. How much for the ebay item? £10.56. And it arrived today after ordering on Sunday......
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Just seen a very tidy 1971 Triumph Daytona with a few bits missing (mufflers ,covers ,speedo/tach) go for $5000..........reckon some dealers will be sweating a bit............see some auction results from UK too .......owners here asking $20k + for Velo Venoms far of the mark.....UK auction sales of tidy Velos and Gold Stars around $10k A.
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I've just seen on a F-B group I'm on a tidy running Venom in the unusual red and black colour scheme on sale at £5750. No idea how that relates to Oz dollars but I'll bet it's less than 10k's worth.
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A bit over $10k on todays rate......the card co gave me 49 p when I bought the valves .........anyhoo,you wont find any kind of 500 Velocette here under $25k (12k GBP).........there is a 350 AJS on ebay now with a start of $16k/8000GBP.....and no ,its not a 7R.
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.there is a 350 AJS on ebay now with a start of $16k/8000GBP.....and no ,its not a 7R.
Imported from the UK. !
That alone would have cost him an arm and a leg.
The "1938" Norton there for $25k would take some beating. ?
The days of pirates about may not be be over....
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You should check out the results achieved for old British bangers in the latest Shannons sale that finished a week ago.
Lot 108, 1950 Matchless G80, $7,200. Lot 109, 1953 Matchless G9 500cc twin, $5,100. Lot 115, 1952 Triumph Thunderbird,$14,500. Lot 116, 1953 Ariel Square Four$17,000. Lot 121 Triumph X-75 Hurricane, $40,500.
The other eight Brit bikes didn’t sell
Those are actual sale prices, not eBay dreamer stuff. $16,000 for a 350 Ajay! Tell’im ‘e’s dreamin’.
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Anyone know what Shannons sellers comission is? ...........have to be at least 10% ,Id imagine ,possibly more .