Hello all, new to the forum, hoping someone can help.

I finshed restoring a 1942 Ex RAF WD G3L towards the end of last year. I ran the bike for a while on the original Amal 275 with the spacer plate at the bottom of the barrel still in.

All seemed ok but not much power, so fitted a new 276 and removed the plate - a lot better.

Went out for a ride and she nipped up at about 50mph.I caught it quickly though. Let it cool and she started and I rode home. Decided to have a rebore to +20 with a NOS original piston.

TL engineering did the rebore and gave a clearance of 4 to 5 thou.

Took her out for a spin and the nipped up again!

The oil is returning OK, I've checked the feed to the head, thats OK too. Have whipped the oil pump and pin out and they seem OK.

I've stripped her down again and the piston is slightly marked on 4 equally spaced areas of the piston.

I've removed the cylinder oil feed valve comprising ball, plug and spring, they seem good.

I'm stumped now! The ony thing I'm wondering about is the feed to the cylinder through the ball valve. Cant see any oil coming out when cranked over. Is this critical?

Sorry for the long winded explanation!

Cheers...........Shaun.

email (option): shaunevans1409@aol.com

Hi Shaun. I would say that 4-5 thou clearance for an original piston is more than adequate. Maybe your engine is running over hot? It's very important that your ignition timing is correct and not retarded. Also have you got your carb running ok and not too weak? Ron

email (option): ronpier@talk21.com

My g3l did the same on a weak mixture the amal book will tell you the right jet somebody on this site will have one .Like ron says check timing then check it again.

email (option): cooperbaumber@yahoo.com

My A.J.S. did this a while back, so I took it apart, checked the timing, cleaned everything up, made sure the oil lines were clean and everything was working well and when I put it back together, it was fine and fingers crossed it has been ever since. I can't tell you exactly what I did to fix it, but as Ron and Stephen have suggested, it was probably the general timing and set up?

To retime engine first set points gap 012 inch both valves closed .undo mag drive nut and free of drive cog.set piston to top dead centre put a pencil in plug hole and mark pencil flush with top of spark plug hole. Take out pencil and mark 7/16th above the first mark.TURN ENGINE BACKWARDS until the top mark is level with top of plug hole.SET TO FULLY ADVANCED WITH LEVER. Get a fag paper turn points till it just lets go of paper do this slowly. without breathing tighten up the mag drive nut do not let anything move .Tip to turn engine put in gear and turn rear wheel. I run lead additive and a bit of two stroke oil with the petrol unleaded is as dry as billy whitlams dog.

email (option): cooperbaumber@yahoo.com

I used to use lead additive, but stopped and I can't see much difference with the running? I know some people use it and some don't, now there's a big discussion in itself!

Who's Billy Whitlam and what's wrong with his dog?

Lincoln Bill

I used to use lead additive, but stopped and I can't see much difference with the running? I know some people use it and some don't, now there's a big discussion in itself!

Who's Billy Whitlam and what's wrong with his dog?

email (option): cooperbaumber@yahoo.com

You've been talking to Robin!

I seem to remember something about the original pistons nipping up on them that I read in a "motorcycle" green un dating from 1944 (it was on here a year or so back). but I think the clearance was adequate at 4-5 thou. Could it be that there is muck in the threads on the barrel and when you tighten them up, it dosen't crack them open, but "bulges" them out a little which could be why you have 4 scores on the piston, do these line up with the bolts?

email (option): davmax@ntlworld.com

hi Dave,what a great thought,i was wondering why four marks.how did you get on at Telford?
cheers rick

email (option): richardholt@rocketmail.com

Rick, I bought a spare engine for my James ml, but that's another story, when I get it back you'll see some pictures of it on the for sale and wanted page. The big pain there was trying to get the stuff you bought out of the place, they wanted you to drag anything you bought through the hall up and down stairs, so I left everything I bought with my mate.

email (option): davmax@ntlworld.com

Hi all and thanks for your replies,

With regard to the carb, it is a new 276 B1J and is set up with the correct jets & needle. I'll try lifting the needle up a notch.

I've set the timing up as per Stephen's guide but set it to 3/8" as per the book I have. Should I go to 7/16"?

The 4 marks on the piston do indeed line up but the threads are as clean as a whistle and the bolts go in easily by hand.

Maybe I'm getting hung up about this ball valve feed to the cylinder, but it has been suggested to me that the timing side bush has a hole in it which supplies this assembly? I've removed the spring & ball & put some oil in the hole but it doesn't seem to go anywhere, the level stays the same.

When a timing side bush is fitted does anything have to line up?

Thanks..............Shaun.

email (option): shaunevans1409@aol.com

What year is your book mine is 41 g3l and it says 7/16th before tdc but you wont get it bang on so i would say 3/8 is ok. Is it sending oil back to the tank.Dont have it on the side stand when running it will just fill up with oil.

email (option): cooperbaumber@yahoo.com

Hi, Stephen,

My book is also 41-G3L and it says 3/8" !

It is version 101-MCI (top right hand corner of cover).

Oil returns to the tank OK and it has not been on the side stand yet!

Cheers..........Shaun.

Ed Abbott had a similar problem with his G3L initially I believe...perhaps you should mail him?...Ian

email (option): ian@wright52.plus.com

edd@abbottracing.com He's very helpful and knows his Matchless pretty well....Ian

email (option): ian@wright52.plus.com

hi shaun,i have just looked at the G3L lubrication diagram in the Matchless
manual (on line),as i thought the main lube is created by oil being thrown up
from the revolving crank.there is a supply fed to the cylinder base,is there no way of checking there is flow there? i presume the oil exits through small holes
are these situated away from where the piston is marked? obviously there is a reason these were introduced.
cheers rick

email (option): richardholt@rocketmail.com

Sent you e mail of a genuine handbook

email (option): cooperbaumber@yahoo.com

Hi Rick,

The supply fed to the cylinder base does exit through two small holes at the rear of the cylinder. I've been unable to check if there is a flow. I've removed the ball, spring & collar & filled the hole up with oil to see if it drains but it doesn't. Compressed air down the hole does nothing either, it seems blocked off.

This is why I was wondering if there could be an issue with the hole in the timing side bush not lining up?

I understand that this feature was discontinued on later models?

Cheers......Shaun.

Hi Rick,

Forgot to add, the holes in the cylinder don't line up with the marks on the piston.

Cheers.............Shaun.

The holes in the barrel do bugger all!They dropped this idea in '56.

Shaun has contacted me direct and i have explained that the problem lies fair and square with the Wellworthy piston design...an extremely light weight design...
Thanks to the slot cut under the oil ring either side of the gudgeon pin boss,that goes round the pistons midrift the skirt sort of hangs off the gudgeon pin boss area...the pistons always pick up adjacent to the gudgeon pin boss where the skirt joins the top of the piston....typically you get 4 contact patches about as big as a finger print contact area.
These will get bigger and migrate down the skirt giving the impression that all the skirt is seizing, if you keep running it...
The solution is really to keep emerying down the high spots until it stops seizing..given that the clearance is 4-5 thou and that the piston is true in the bore and not tipped slightly due to a slightly bent rod...
Boring out excessively will give rise to piston slap eventually when the piston Beds in.
Matchless introduced a "wire wound " piston in 1948 to control this wayward expansion.

Ed

email (option): edd@abbottracing.com

Hi all,

Many thanks to all who have helped with this problem. The advice has been implemented and she's nearly back together.

Will report back after a few runs.(When it's a bit warmer!).

Cheers............Shaun.

Just came across your post and it took me back to having exactly the same problem when I restored my G3L a year or so back.

I had the engine rebuilt by a professional rebuilder using all new old stock parts.. We decided to get the barrel bored out slightly to 20 thou just in case the bore was scored from years in storage. This was done at TL engineering.

When the bike was finished I had the same problem with it nipping up. I contacted the rebuilder and he went through all the usuall what might be causing it problems.

I puzzled with the problem for many weeks until the rebuilder came back to me with the story that he had a similar problem with a second bike he had just finished , again the reborn was done at TL.

Turns out that TL had an apprentice that had mixed up his calculations and bored out to the wrong dimensions. I stripped the bike and sent it back to TL for corrective action. All fine from that point.

Maybe TL have made the same mistake? It proved to be a very inconvenient!

email (option): tim100@pc-q.net

Hi Tim,

The bore & hone was done by Derek at TL. I've had work done on other bikes before by Derek with no problems. When I went back the other day for a light hone, the bore was re-measured and still at 4-5 thou before the hone.

Looks like you were unlucky but glad that the problem is now sorted.

Cheers.........Shaun.

Hi all,

To keep you updated as promised....All running OK at the moment touch wood!

I know it's early days and I've only ridden about 60-70 miles so far, but she seems free enough and has shown no signs of nipping up.

Been keeping her at about 45 mph, not stressing her too much.

I Rubbed the 4 marked areas on the piston down, and had a very light hone. I've been running on a 50:1 fully synthetic 2 stroke mix to keep things nicely lubricated.

Hopefully if I keep this up she should be OK.

Thanks again to all that gave help

Cheers...Shaun.

email (option): shaunevans1409@aol.com

i had the same problem last year on my g3,honed it out to 5 thou as it was a little tight and run it on 80 to one two stroke mix as its a new engine and is been fine

email (option): adriancrossan@tiscali.co.uk