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

Helpful information and requests for assitance and advice
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

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

Post by Mick D »

Hi

It sounds like a weak mixture - partially blocked pilot jet or leaking inlet tract - check the spark plug colour, if it's a light grey this sort of confirms the diagnosis.

My first port of call would be the pilot jet.

Regards Mick
bikeserv
Posts: 5
Joined: Thu Jun 01, 2017 4:45 pm
Location: Cyprus

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

Post by bikeserv »

I already did most of what you guys say:
Pilot circuit is clean(checked it more than 3 times)
Checked cam timing twice
Checked valve clearance both cold and hot
Adjusted ignition with a dial gauge to find more accurately the ignition point
Checked spark strength
Sprayed carb cleaner to the intake spacer for any leaks
The plug is always dark and oily,on any setting of needle,pilot screw or even main jet.
Will not start without choke,even though our weather here is pretty hot now.
Adjusted points gap and rechecked them multiple times
I have tried all the jets and cutouts that come with the carb.
My theory now is that the cylinder/piston or valve guides seep oil,and maybe that is a reason that i might have good compression even if i might have a leaky intake or both valves,and an oily spark plug.Also,i dont know how difficult the kickstart have to be but i can start it with my hand if i push it a bit hard,i dont feel that much of a compression.But my point of reference is newer bikes so...
Thank you guys for all the replies.Will keep working on it and see what i might find,i have this thing to always find what is wrong because i love my job :)
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

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

Post by Rob Harknett »

Am I correct in understanding, you can start the bike with your hand without using the decompression lever? You said compression was good, I would say that is very bad. Could be broken rings, head gasket blown so plug is always oily. The bike may also backfire starting with the AR lever fully advanced. The bike needs to warm up before the lever is fully advanced. If you start fully advanced, then just ride off, if you close the throttle to slow down, the will engine will probably stop.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

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

Post by SPRIDDLER »

Hmm, well you've done all the right things so I think we need to go back to basics as it's difficult to visualise/diagnose problems remotely and without knowing any history.....

1. Has it ever run satisfactorily for the owner or for you?
2. Why did the owner find it necessary to 'take the top off'?
3. Did the owner replace the previous carb with the Concentric? If so, does he still have the old one?
4. How did you or he know how to check the cams/valves timing?
5. Did you set the ignition timing at 3/8" BTDC (which is o.k.) with the handlebar Advance/Retard lever set to 'Full Advance'?
6. Is the inlet valve oiling screw set to a max of about 1/6th of a turn open?
7. Have you or the owner had the cylinder barrel off and/or checked the piston/rings?

It's concerning that nothing changes regardless of which set of carb internals are used and that it will only run on full choke and the plug becomes heavily fouled (with oil it seems).

Ref the 100psi. It may be a bit low but don't think this is the main problem, (especially at kickstart speeds). These bikes are low compression (c. 6:1) and made to run on low octane wartime petrol. There is a guy in our club whose party trick is to start his 1952 G3L by hand. In any case you mentioned that you had 'done the valves'.

On the well-known basis that many carb problems turn out to be ignition and vice-versa, and since you haven't yet managed to get th'engine running other than slowly and very roughly, a couple of quick (and probably irrelevant) things are worth checking...

a) By now the plug will have been thoroughly contaminated and maybe you've cleaned it a few times so as a matter of course I would fit a new one. Modern plugs do not respond well to cleaning (certainly not with even a soft wire brush) as nowadays the insulator around the central electrode isn't glazed and becomes scratched so that when under compression in th'engine the spark tracks all over the place or shorts internally or fails to spark at all.

b) The plug cap should not be one with a suppressor and the H.T. lead copper cored, not the modern carbon cored type.

That'll do for now.

Hope you're still loving your job ;)
'There is a tide in the affairs of men
Which taken at the flood............'
bikeserv
Posts: 5
Joined: Thu Jun 01, 2017 4:45 pm
Location: Cyprus

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

Post by bikeserv »

Goodmorning,Monday was a holiday so today i got back to it.
Read your replies and:
the owner is of third generation,and he innitally took it apart to build it himself.Bike didn`t run,so he took it to another mechanic at first,were the carb was replaced and the bike was adjusted to work with the air valve closed.Still it didn`t run ok so he brought it to me.
I adjusted ignition timing(with lever fully inwards-advanced) and valve clearance per the manual
Opened the right cover and checked cam timing per the manual
Only thing i havent done anything with it is the inlet oiling screw,which i will check today,along with a new spark and also check the plug cap.
This is a nice and difficult situation with this bike,so am looking forward to find out what is wrong with it.Its really interesting :)
Thank you for your advices
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

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

Post by SPRIDDLER »

bikeserv wrote:Goodmorning,Monday was a holiday so today i got back to it.
Welcome back to the challenge.

1.
the owner is of third generation,and he innitally took it apart to build it himself.
Did he strip and rebuild the engine or just the cycle parts - frame, tinware etc?

2.
Bike didn`t run,so he took it to another mechanic at first,were the carb was replaced and the bike was adjusted to work with the air valve closed.
This would seem to suggest a carburation issue - jets, float height (i.e. it could be that the fuel level in the float bowl is too low).

3.
I adjusted ignition timing(with lever fully inwards-advanced
To advance the ignition operate the handlebar lever so that the cam plate (behind the c/b points) moves in the opposite direction to that which the points rotate.

4.
Opened the right cover and checked cam timing per the manual
Which manual do you have?

5.
Only thing i havent done anything with it is the inlet oiling screw,which i will check today,along with a new spark and also check the plug cap.
The oil screw and plug cap are unlikely to be the cause of the non-running but at this point it's worth eliminating anything which may exacerbate the problem.

--------------------------

It's frustrating at this distance from you. We have a contact in Cyprus: C Constantinou Alasias 21, Limassol, who may be able to put you in contact with a local owner who may be able to discuss the problem with you. Unfortunately I have no phone number for him.

Alternatively, I notice that there are three WD G3L machines in the Classic Motorcycle Museum in Nicosia.
Image


Perhaps someone there has experience of these machines or may let you check them or could put you in touch with their owner(s)
http://museum.motocy.net/

Rest assured we're not giving up on you (!) but diagnosis by crystal ball is not ideal, especially with so much unknown. No offence intended but I know from my own senior moments :oops: that when checking your own work it's easy to overlook a basic mistake which is obvious to someone at your shoulder.

Of course you are using fresh petrol ;)
Last edited by SPRIDDLER on Tue Jun 06, 2017 5:55 pm, edited 5 times in total.
'There is a tide in the affairs of men
Which taken at the flood............'
User avatar
1608
Member
Posts: 2493
Joined: Mon Oct 05, 2009 1:00 am
Location: ESSEX UK

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

Post by 1608 »

I had the same thought as Spriddler, re the A/R. Are you sure that a tight ( pulled ) cable is advancing and not retarding the ignition. It does differ on different models and years I believe.
Bruno
Posts: 48
Joined: Tue Jul 07, 2015 9:42 am
Location: ABERDEENSHIRE UK

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

Post by Bruno »

Hello Constantinos,

This suggestion is so obvious that it may sound ridiculous ... but it might just be your problem. Is your ignition switch possibly set on the 'emergency' position instead of the 'ignition' position? I had very similar running problems and symptoms that you describe with my G3 when I initially got it. Wouldn't idle or run evenly, backfired and died when giving it throttle.

I eventually discovered that the wiring to the ignition switch was the wrong way round! Re-wiring it correctly eliminated all the problems.

I appreciate you are an experienced 'spanners man' and hope you are not offended by my suggestion - at this stage it's either something so simple you'd never think of it, or something pretty serious (hopefully not the later).

Cheers, Bruno
User avatar
dave16mct
Member
Posts: 3234
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

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

Post by dave16mct »

No ignition switch on a WD Bruno. It's got a magneto.
Dave.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

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

Post by SPRIDDLER »

Bruno wrote: Is your ignition switch possibly set on the 'emergency' position instead of the 'ignition' position?
I'm with you that we're getting to the stage of having exhausted all logical possibilities.
However, the '41 G3 would have had a magneto and dynamo and whilst I'm very familiar with all civvy singles I've not had much to do with the specifics of the WD version, but I'm pretty sure that the 'EMG' facility was only available on later alternator and coil models. Happy to be corrected and learn though.
All thoughts, daft or otherwise are very welcome. Keep 'em coming :beer:

EDIT
Thanks Dave - our posts crossed.
'There is a tide in the affairs of men
Which taken at the flood............'
Locked