Engines G3 Compatibility

[chtijr]

Hello Everybody
I am new on the forum and trying to write in English from north of France .
Thank you in advance for help i hope members will give to me .
Sorry for my poor English language.

I have got a MATCHLESS G3Ls 1957 since i was 18 years old and now I am retired
and I would like put it on the road again .
The engine is not running and i found a other one not complete for sale but I need advise .

Do you think it is possible to put my 1957 Magneto witch is on the front on an older engine ,
certainely a G3 or G3L from the Forties , witch a cast iron head cylinder and decompresion
control lever on the right witch has normaly the magneto on the back ?


Thank you very much

JR

[clive]

Hi JR and welcome. Not sure I fully understand your question but here goes. The magneto for your 1957 G3LS, if correct, would be an SR1 with auto advance/retard. The magneto for the 40s or early 50s Matchless behind the barrel would be an N1 with manual advance and retard. The SR1 will not fit behind the barrel but if it did there would be no way of fitting the auto advance retard. If however you were thinking of using parts of the engine on your 1957 bike it may be possible to use the later timing cover in front of the engine with the earlier crankcase. That way you can keep the SR1 mag. You would probably need to use the later cylinderhead as the exhaust pipe angle is different on the iron and aluminium heads.
Hope you can understand the English.

[clive]

Just reread your post and seen that the decompression lever is on the crankcase. I cannot say for sure that the later timing cover would fit so you would have a problem with the magneto. What is wrong with your engine? You may be better trying to fix that.

[chtijr]

Hello Clive

Thank you for your interest

According with this picture, I think all your advises are correct .

https://www.dropbox.com/s/d0p6aga6d6zhg ... l.jpg?dl=0

It seems that this engine could run properly even the sailer is not abble to confirm that .
It would we better to set my aloy head cylinder to fit the original exhaust pipe and later carb .

I think i can buy this engine . Do you think also ?

Than you very much

JR

[clive]

if you want to get your 57 bike running I think you would be better to find out what is wrong with that engine and mend it. Although some parts are common across the years many are not. You do not say the price and your picture does not show (I think only paid up members can post images). If the seller cannot confirm the engine runs why take on a second possibly non working engine? Fix the one you have unless it has had a major disaster. so no I would not advise buying an engine of the wrong year that is not working.

[alanengineer]

Repair the origional engine unless the crankcase has serious damage that cant easily be repaired. All of the other bits that you might need can be obtained.
Why do you think the '57 engine you have will not work

[chtijr]

if you want to get your 57 bike running I think you would be better to find out what is wrong with that engine and mend it. Although some parts are common across the years many are not. You do not say the price and your picture does not show (I think only paid up members can post images). If the seller cannot confirm the engine runs why take on a second possibly non working engine? Fix the one you have unless it has had a major disaster. so no I would not advise buying an engine of the wrong year that is not working.

Ok Thank you for your message.

In fact , my 1957 bike is in very very poor condition from the front to the back .
I need imperatively also the fork with the Wheel an front brake witch are wrong on mine .
My engine has to be entirely reconditionned . The crankshaft has broken , and the engine is
dismounted in several boxes for 20 years at least .

My oportunity is to buy a quite complete bike not running in rather good condition , ( but whis this special engine )
for approx 1000 Euros .
Idéa is to have spares parts to make one running with the two .

Thank you

[alanengineer]

1000 euro is good for an almost complete donor bike, but for it to be any help at all, it needs to be similar years of manufacture. every year, something changed, so you could end up with two projects that never get done. How close to Calis are you.

Think about coming across to the Jampot rally being held in Kent this year. lots of answers to questions available all over the site

[chtijr]

fail to post a picture but hope you will be able to open the web page with an URL

https://www.dropbox.com/s/d0p6aga6d6zhg ... l.jpg?dl=0

Bye

[chtijr]

Hello everybody

Seems that it is ok now to see the picture i wanted to post .

So , i return back to my first and main question :

Do you think this engine with an older crankcase but with the 1955/57 magneto
already setted on , have a chance to run properly on day ?

I think yes from my opinion , but you are the specialist .

Thank you very much for your interest .

https://www.dropbox.com/s/d0p6aga6d6zhg ... l.jpg?dl=0