Matchless 41-G3L First time working on one of these..

Helpful information and requests for assitance and advice
bikeserv
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Location: Cyprus

Matchless 41-G3L First time working on one of these..

Post by bikeserv »

Hi
My name is Constantinos and I have a small motorcycle workshop located in Cyprus.I have a problem with a G3l and since i have absolutely no experience on any of these bikes i thought of asking you guys for any tips or previous experiences.
My problem is that this bike will not idle with the air open.Carb is clean,it has a AMAL 626/300,with a couple spacers to clear it from hitting the magneto.
I have good compression(nearly 100psi warm)did the valves,set ignition timing 3/8 and set the gap at 12.Bike starts easily with slight retard and close air valve.But when i open the air valve it stumbles and dies,and if i rev it it backfires through the carb.Carb settings are 160 main,0.106 pilot,slide #3,needle on 1st,pilot 1.5 turns out.
I`m out of ideas,since no matter what i do to it it does the same.Since the owner took the bike appart an rebuild it himself,i thought it would be a good idea to get some opinions from guys who know and are experienced into this sort of bikes.
And maybe learn something new from it.
Thank you in advance
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Expat
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Re: Matchless 41-G3L First time working on one of these..

Post by Expat »

Hi Constantinos,

Just a complete guess really as I have no knowledge of that year of bike but if the clip is in the top groove of the needle, the mixture may be far too weak. :(

Have you tried moving it down a couple of grooves?

Regards,

Steve
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SPRIDDLER
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Re: Matchless 41-G3L First time working on one of these..

Post by SPRIDDLER »

Welcome, Constantinos. We'll try to help you.
This was military WW 2 machine but to avoid any confusion would you advise the engine numbers which are normally at the left side of the crankcase just where the base of the cylinder joins it. The numbers may be on a brass plate in the same place or (and it's very unlikely) they may look something like this:
Image

Did the owner strip and rebuild the engine (remove the valve cams/gears etc)?

You obviously have experience but I have to ask if are you aware that to put the choke 'Off' you move the handlebar lever so that it 'pulls' the cable tight? (Don't be offended - it is a common misunderstanding!). As you are no doubt aware it now has a 'modern' AMAL Concentric carb, not the original AMAL 276 carb which had a separate float chamber but many use the Concentric which will work fine.

If it helps you can find the military workshop specifications here:
http://archives.jampot.dk/book/Workshop ... ndards.pdf

and the military 'Users Manual' for the 1941 G3L here:
http://archives.jampot.dk/book/Owners_m ... n_Book.pdf

and here's AMAL's illustrated guide to servicing the 600 series Concentric carb:
http://amalcarb.co.uk/rebuilding-mark-1 ... arburetter
Last edited by SPRIDDLER on Thu Jun 01, 2017 11:14 pm, edited 1 time in total.
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Rob Harknett
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Re: Matchless 41-G3L First time working on one of these..

Post by Rob Harknett »

I wondered what carb that number was for. I have no idea how that should be jetted out. Or how the choke works. If you had the correct carb I would have thought it jetted and set up about right. I would have then said, check you have the correct throttle slide.
http://archives.jampot.dk/technical/Car ... 54_AMC.pdf
Above are settings for the correct carb, but they are no help for you.
bikeserv
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Re: Matchless 41-G3L First time working on one of these..

Post by bikeserv »

Thank you all for your replies.The number on the engine is 40SP 8035 and has G3 written below it.The number is stamped on an aluminum plate.I have tried the needle on all 3 positions without any difference,also tried all 3 cut outs with #3 making far less backfire.I`m thinking that i might have a leaking intake valve,because the way the engine is behaving its like it would if i had a tight valve clearance.But since the valves are adjusted ok,i would think more that the valve is leaking.The owner took the top end off,so i dont know about ring end gap,piston clearance or condition of the valves/seats.So even though compressios test was ok i m leaning towards a leaky valve.
Again,thank you all for your replies,i always like to learn more about my work,either new or old machines.
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Re: Matchless 41-G3L First time working on one of these..

Post by SPRIDDLER »

The actual meaning of WD engine numbers are better known to others, maybe Rob H can throw some light on it.

Valve clearance (measured at the top of the pushrods) with a warm engine should be 'Nil' but with the pushrods free to spin. However I've always set the clearance that way on a cold engine with no problems occurring.

As far as the carb is concerned, the engine is supplied only by the pilot jet up to about a third throttle opening. The pilot jet and drillings are small and easily become blocked or gummed up so it is vital that they are checked thoroughly.

With two carb spacers (not in itself a problem) there is a risk of an air leak weakening the mixture. If you can keep the engine running try spraying some WD40 on the spacers/manifold and if the engine speed or note changes or you get a smoky zorst it may indicate a leak.

As an aside it occurred to me that at this time of year in Cyprus (30degrees?) you shouldn't need to use the choke for starting!

Let us know how you get on.
Last edited by SPRIDDLER on Fri Jun 02, 2017 11:04 am, edited 1 time in total.
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Rob Harknett
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Re: Matchless 41-G3L First time working on one of these..

Post by Rob Harknett »

There is a problem identifying numbers on WD machines, other than those stamped when the machine was first built. Many things could have happened to it. I could had been captured and re stamped. It could had been re captured and re stamped yet again. It could had been repaired or had a replacement engine, again re tamped. This would had went on for the whole time during the war. At the wars end it may had been found and parts used to repair or rebuild it. It would then need to be registered for civvy road use in, perhaps Cyprus. Again it may have been re stamped and registered to meet that countries requirements. Some bikes were sold off by the war Dept as late as the mid 1950's. These bikes were usually reconditioned. Again perhaps using replacement parts like an engine, that was again re stamped. All this history often finds a part gets a stamping that cannot be identified. To sum up, if a WD bike does not have its original stampings, which can be confirmed by surviving records. It is almost impossible to confirm its history. Some machines that did go through WD workshops even had new numbers stamped on a plate, that was riveted inside the toolbox. After 77 years, that toolbox may have survived, even with the plate still inside, on any bike other than what it was originally fitted to.
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Re: Matchless 41-G3L First time working on one of these..

Post by SPRIDDLER »

I've spoken to Burlen, the AMAL distributor who advise that the spec'n used successfully on the WD G3L for a 626 (i.e. 26mm dia throat) Mk.1 Concentric is......

Main jet: 130 This probably when the WD air filter is fitted. I guess the larger 160 jet which you have would be for a carb without a filter.
Pilot jet should be No. 20 if it's an 'early' 626 carb which has a replaceable pilot jet. In later Concentrics this jet was a fixed non-removable bush.
Needle jet: 0.106
Slide: 3
Middle notch for needle clip.

I see that the original type 275 AMAL carb had a 7/8" (22.2mm) throat diameter and you have the 626 which has a 1" (26.0mm) throat diameter but I doubt that this would be the cause of your problem. As mentioned above, the 626 has been successfully used on the WD G3L even though there may be a mismatch between the diameter of the carb spacer(s) and carb throat.

Here's AMAL's technical drawing of the 626 with parts indexed...

http://amalcarb.co.uk/downloadfiles/ama ... d_Tips.pdf
Last edited by SPRIDDLER on Fri Jun 02, 2017 11:52 am, edited 1 time in total.
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jack clegg
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Re: Matchless 41-G3L First time working on one of these..

Post by jack clegg »

Backfiring thru the carb could be a symptom caused by incorrect inlet valve timing. Best to check if it's been fiddled with/incorrectly assembled. TTFN Jack
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Re: Matchless 41-G3L First time working on one of these..

Post by SPRIDDLER »

jack clegg wrote:Backfiring thru the carb could be a symptom caused by incorrect inlet valve timing. Best to check if it's been fiddled with/incorrectly assembled. TTFN Jack
You're right, Jack. I did ask him about that in my original post but he recently said that the owner only 'took the top end off'.
Of course we don't know when or if the engine has run at all during the past 75 years or if this is a recent problem. :?
Last edited by SPRIDDLER on Fri Jun 02, 2017 6:31 pm, edited 1 time in total.
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