classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: geoff.godwin on November 30, 2023, 05:13:49 PM
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I have owned the bike for 40 years and have finally tried to get it on the road [last used in 1940] It is the twin port ohv model .with AMAC carb and Sturmy archer gbox. I have set the cam timing such that the valve overlap is equidistant either side of tdc. Set the mag to spark at about tdc. I get it to fire but not for more than about 5 seconds. The carb is 2 lever [big lever goes to big slide .little lever to little slide. I have not had a bike with two slides and am not sure of basic setting for starting .If I ever get it running properly riding will be a challenge with lever throttle and hand change! Is there any body on this forum with knowledge of model 355 or some basic settings to get it to run properly. cheers Geoff
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If you can get it to run for ~5 secs Geoff, then your basic settings must all be in the ballpark, as they say.
Without knowing this exact model, in the slightest, my advice would be to tickle it and tickle it and tickle it
some more, esp once it fires, see if that makes a difference. ?
And/or drop the air slide down some more - it will likely need a good dollop of choke for a cold start.
Esp after 80+ years of hibernation !
Might even need the air slide down to its maximum, for a short time anyway.
We assume you have inspected and thoroughly cleaned the carb at some previous point.
Any gummy deposits or traces of corrosion inside need to be banished, forthwith !
Have fun !
We look forward to a pic of its 1st outing ...
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Solid advice from R to which I will add a few comments.
1929 was the last gasp of the AMAC name. By then it was close to the then new Amal carb and was well past the continual two lever juggling of the veteran era. You may use the little lever for a cold start and warming up but will mostly ride on the big lever alone. That will come with practice.
Starting commonly needs the big lever cracked open a little.
As you need to take your hands off the bars to both give hand signals as well as change gear you will soon appreciate how practical and effective a lever throttle is. This is not the place for a self closing twist grip.
Regardless of what you ride now you will find your 1929 bike requires an entirely different technique. Not better, not worse, just different. You are starting afresh in a different world.
What are the engine lubrication arrangements? That may require discussion as well.
Welcome to the club. It’s like putting on “L” plates again. All new and exciting.
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A bit more spark advance?.........generally the 2 lever carbs needed the choke set fully on with the long and short lever closed ,and then both levers are opened together until the engine is hot ,when the choke (short) lever can be open until rapid acceleration is needed ,then the short lever can be closed slightly .
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Many thanks for the replies, The oil system seems to be total loss with an adjustable output pump mounted on the magneto chain case. It sounds as if I may be on the right track anyway. I should just mention that its not just the bike thats been off the road for a long time , I sold my velo mac when I went to uni in 1966!! and yes I know the roads are busy and yes MUM I will be careful .Geoff
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Bit of an update, I can now get it to run for longer periods But only at very fast idle or more . Any attempt to reduce and it dies ,I have tried the pilot jet screw [recommended 1/2---3/4 turn open] it affects the idle speed but not a lot, the engine runs fine at the higher speeds but as the speed reduces it hunts all over the place. I am now wondering if my valve overlap set equidistant from tdc is correct. The only possible cam settings are about 15btdc inlet/15atdc ex 5btc inlet/ 25atdc ex or25btc inlet/5atdc ex With quite a gentle cam I would expect the idle to be much slower and consistant . The other thing I find a bit odd is the size of the AMAC ita a !inch bore on a 350cc single which seems big to me . I am starting to get better at starting but still have bother trying to catch it when it fires . Geoff
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Have you explored the float height setting and fuel delivery system ?
Or tried that tickle it and tickle it suggestion.
Especially when it sounds like it is starving for fuel at low rpms...
Checking that the pilot jet system is clear and unobstructed would be #1 on my suggestion list.
Carbs left standing often need much cleaning to be put back into service.
Or is that MUCH cleaning.
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The fuel level in the carb is fixed [the valve stem has only one circlip position] I have checked the fuel level is at the top of the main jet ,which is as Amac paperwork .I have cleaned the carb several times and checked the pilot jet ways . Geoff
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Hi Geoff,
I've re-read the above, but still not sure where you're up to. Is everything OK at higher speeds - will it rev, ride down the road, accelerate etc? If so that rules out lots of things. If not, that's a better place to start than getting a good low idle.
The 1" AMAC carb is presumably a T25MDY (or X if its top feed). This is usually stamped on the body somewhere, maybe near the mounting flange. If so this is the standard touring carb, with the air adjustment with the little slide on the side of the mixing chamber. Royal Enfield went to AMAL carburettors in 1930, and the 350 ohv used 6/004 body, 15/16" bore, 130 jet, 6/5 slide, needle position 3, and 14/079 float chamber. So the 1" size is about right, if a bit on the large side. Re jet: 130 AMAL = 36 AMAC = 0.038"
Don't forget that the needle in your throttle slide may or may not be the correct needle or at the correct height. AT least check that the needle is well clear of the needle jet at full throttle.
Leon
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I would be giving the ignition system a closer look. The old remark about so many fuel problems being ignition has a lot of truth.
You wrote earlier the bike has been off the road for 40 years, old electric equipment doesn’t age well. To me it is all suspect , magneto, HT lead, etc, etc. You also wrote you had set it to fire about tdc. I think that’s far too late. Somewhere about 3/8” at full advance is a better starting point.
Resurrecting an old beast can be a quite an exercise as you are finding out. But satisfying.
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The carb is a 15mdy the jet needle is unmarked but set to mid groove . The mag is non original mo1 but gives a good 5mm spark spun by hand or drill. After the earlier advice I started to use about half range on advance,about 10/15deg . The other slightly odd symptom is that I have good compression with throttle closed but less with it cracked open? Geoff
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Hi Geoff,
Yes T15MDY sounds good - 1 1/8" throttle valve, and presumably 1" choke. The T25 I mentioned would be too small...
The compression thing is weird.
Re the ignition timing: The bike might run with all manner of timings, but it will only run properly if the spark is set at something like 35-40 degrees (probably 3/8" or so) BTDC fully advanced. There's no need to experiment.
The valve timing sounds OK at 15/15.
But is the engine in good order? It should have good compression - hard to move over TDC with the ks lever when the throttle is open. Maybe it has a burned valve? Or worn-out valve guides? Or worn out cylinder/rings? Or no valve clearance? Or no oil?
The last one worries me. Not sure how the oiling system works on a 1929 Model 355 (still total loss? or is there a scavenge pump to put the oil back in the tank? By 1929 most bikes had gone dry sump) but hope you've got it sussed out. I'd say the most important part of recommissioning any bike is to make sure nothing bad has got inside (like a wasp nest), that the oil tank is drained, cleaned and filled with new oil, and that the oil pipes and pump are clean and functioning. No compression can be a symptom of a very dry motor; maybe try a squirt of oil down the plug hole and see if the compression comes back. If the motor is still total loss, there should be at least an eggcup of petrol in the crankcase anytime it is running. If it's dry sump, make sure the oil is returning to the oil tank is a steady stream within 10-20-30 sec of the engine starting.
Leon
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I just had a look. Nice bike, but no dry sump until 1930, so do be careful it's feeding enough oil into the engine. Funny in this era when there's no hand pump to help out... Interesting that the spec says AMAL but the drawing shows AMAC MDY - 1929 was the change over period and lots of bike still used AMAC even though the AMAL was said to be available.
Once you've got compression and checked the ignition timing, it would be worth cheching for air leaks around the carb and inlet manifold as it won't idle if it leaks.
Good luck.
Leon
Edit: Or maybe a valve is sticking at low speed - make sure they're not rusty and give them a squirt of something
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Thanks for the sound advice fellas, The engine is in reasonable nick, the piston/rings are fairly worn ,but from memory it is out at +40 .I toyed with the idea of a rebore or resleeve BUT ive heard horror stories of old cast iron pots cracking as a result . Looking around there are not a lot of 1929 355 barrels about . The reason for the one month delay on this update was a buggered calf muscle from when I forgot to retard the mag on starting ,boy that hurt!! Cardan I just picked up on your earlier post about the main jet .038 is 1mm as near as the main jet fitted is unmarked but I think less than 38thou Geoff
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The main jet has very little effect, except at or near full throttle !!!
You still haven't said if you have actually ridden it on the road.
Nor said if you have tried tickling it to get a better idle.
Thats a good quick-n-dirty test to see if its suffering fuel starvation
Otherwise, that suggestion of exploring the ignition is a good un ....
Even if it does throw a good spark - outside the combustion chamber.
P.S. Getting a good idle is also generally dependent on getting the engine up to temp.
If its coughing and spluttering or hunting with the engine stone cold,
then all bets are off. Thats when it needs some choke - or extra tickling !!
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I have not ridden it yet as I cant keep it running for long enough to feel confident . I have not ridden any bike for more than 50 years ,the thought of pushing it any distance at 75 is no fun at all . Tickling does not seem to change anything apart from a puddle on the floor. The problem I am finding is the balance of the two levers against mag advance. On my old car static advance is 0 increasing to about 35 at 2k+ if I try to get the car to idle with full advance it wont. So I try to get the bike to ilde with starting advance say 10/15 btdc . I have looked into an induction leak ,but will try again ,the inlet duct is about 6in long to clear the dynamo. Geoff
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That's a super nice bike Geoff - looks very original.
I'd be happy to drop by and lend a hand, but I suspect I'm 10,000+ miles away which makes it hard. Maybe there's someone nearby with experience with vintage bikes? It would be great to get it running nicely.
Good luck.
Leon
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That is a nice bike.
I'd swap for any of my Enfields (later), any day of the week.
But I'm also 10,000+ miles away ...
A dab of grease or 2 well applied to the carby spigot may help (briefly) with any air leaks.
Just to try. And is easily removed.
A wipeover with oil on the chromy bits (nickel ?) will help prevent any further corrosion.
Will need to be wiped well dry before any heat gets to it, or may smoke a bit ...
I'm wondering if you have any later carbs you can try on it ?
Or, once warm enough, if that choke lever would be needed at all ??
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We see that someone in Switzerland is selling off this engine.
My that is a long induction pipe !
Timing cover looks a bit abbreviated ...
https://i.ebayimg.com/images/g/GHQAAOSwnMdloxES/s-l1600.jpg
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That is the 500cc version of my 350cc, the huge long inlet pipe maybe one part of my problem ,being so long it will take a long time to reach a stable temperature ,with the fuel mixture condensing out on the walls of the pipe [its bloody cold here at the moment].. Yesterday I ran the bike for a good while started to get a better feel for the many control levers. After it had warmed up i tried again to get it to ldle against all that I know from vintage cars I left it at fullish advance 30/35deg it seemed to work better like that . Still not stable at low revs hunting a lot and in the end it just died ,but a definite improvement. One other niggle is oil system ,its total loss and after running for a while dribbles oily mess into its dirt tray .I would like to check the output of the pump but cant run the engine with it disconnected ? Geoff
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There are quite a few knowledgable guys on this facebook group: https://www.facebook.com/groups/444624876468800 Only way to join is by answering ALL entry questions and agreeing to group rules.
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One other niggle is oil system ,its total loss and after running for a while dribbles oily mess into its dirt tray .I would like to check the output of the pump but cant run the engine with it disconnected ?
Hi Geoff,
You pump has an inlet and an outlet (?), so presumably you can disconnect the outlet pipe and see what comes out when the engine is running. If the bottom of the oil tank is not filled with sludge (and it probably will be if you haven't taken the tank off the bike and cleaned it out) oil should be running out the outlet withing a few seconds of starting. The pump is said to be adjustable, so you should be able to adjust it between nothing and a slow trickle. Normal running might require something like 30 drips per minute, so it would be useful to find the setting that gives this.
The oil coming out of the oil pump should look pristine and golden!
Then you need to find the sump plug and drain everything out of the engine, if you haven't done this already. Do it after the engine had run and mixed things up a bit. If everything is ok, there should be a surprisingly small amount of oil to drain out, say an egg-cup-full.
When you restart the engine there will be no oil in it. Yuk - this is a job for the hand pump in the oiling system but you don't have one! If you can't find a place to squirt in a few squirts from the oil can, at least set the oil pump to its highest setting for the first minute or so of running, and don't rev the engine, before cutting it back to the 30 drip per minute setting.
No oil should be coming from anywhere at this point. If it does, you have an oil leak. In a total loss system most excess oil is burned with only the odd drop ending up on the road. If you have oil running out, your oil pump feed might be set to "max". Is the exhaust very smokey?
Leon
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Thanks Leon, in the end I worked out a way of doing it. I removed the pump and pipes and connected a flex pipe between the tank and pump , with a short length of copper pipe flattened at one end mounted in a drill I spun the pump . Almost zilch ,so I looked at the adjuster shaft [dial missing] it was fully shut. I assume that the adjustment is on the inlet . So I undid the shaft a couple of turns and now have a reasonable output. On the basis that oil is cheap compared to bearings I will up the output till the smoke brings complaints .I have bitten the bullet and bought a helmet and inured the bike from 1st march . fingers crossed Geoff
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Hi Geoff,
Just be wary of too much oil: if the crankcase gets over-full with oil everything gets terribly hot and bothered. The trick is finding the Goldilocks flow: not too little, not too much, but just right.
Good luck!
Leon
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Clue...if it's smoking like a WW1 destroyer chasing subs it's over-oiling.. ;)
Not as fatuous as it sounds. I have a Scott (obviously also total loss oiling) and some owners think that having the oil pumps WFO is a good thing, but there's no need for it. A light blue haze when working hard is more than adequate.
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At last ,a dry day and off we go. The gearbox is described as close ratio, wow they were not kidding. No real idea of speed as no speedo or rev counter. All was going really well untill the rather dodgy thread on the gear change connector rod pulled out !! back home in 1st gear. Some smoke but not worth chasing a sub for. Geoff PS 84 years off the road for the bike 55 years for me on two wheels!!
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Congratulations !
On several counts ...
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Nice one Geoff! Hope you enjoy it.
Leon
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Hi Geoff and All,
I have only just now caught up with your posts
I have a fair amount of experience on the AMAC MDY carbs
These have a tapered neele just the same as later Amals, so after starting the bike you should open the air (choke) slide fully, (tight cable) and use the long lever just as you would a twistgrip
Most often there is no need to use the choke (air) lever just press the tickler until fuel starts to drip from the chamber top or bellmouth .
Did you remove the jet block from the carb body and clear the tiny pilot mixture drilling's ,
There is no separate pilot jet just the drilled holes, the drilling's in the block line up with others in the carb body exiting at the engine side of the throttle slide.
Not having a throttle stop on these carbs tickover must be set with the cable adjuster
This alters the speed of the engine as the handlebar is turned which can be a pain
A solution is to use the special outer cable as used on modern bicycle gear changes, this is wound on a long spiral to prevent the overall length changing as the handlebar is turned.
I have the AMAC instruction book on PDF which I can share with you if you need it
John
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Hi John,
That's interesting - I'd not thought much about the tapered needle in the MDY (1928-on), but it seems this was it's first appearance on an AMAC carb. The tapered needle (usually called "variable jet") arrangement was covered in a 1913 Brown & Barlow patent, and was first used on their 1914 model carbs. So through the 1920s, B&B had models with tapered needles, and AMAC didn't. Until 1928. I wonder if this was part of the AMAL deal, where AMAC, B&B and Binks were amalgamated to form AMAL?
B&B's tapered needle and AMAC's air control on the side on the throttle body were two features used on the AMAL carbs for years...
Anyway, good tips for Geoff.
Cheers
Leon
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Thanks John, I now have a pdf of MDY stuff and it did point me in the right direction. If I am quick enough with the air lever I can catch in one or two kicks. At the moment I am re learning how to ride ,made more difficult by excessive clutch drag. I had to put the bike into a hedge to avoid a homicidal van driver [only at crawling pace mind]. All good fun. Geoff