G3 - Insufficient gap between chaincase and gearbox sprocket

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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G3 - Insufficient gap between chaincase and gearbox sprocket

Postby tippi11 » Tue Dec 11, 2018 11:02 am

Hello,
I have a problem with the back half of the primary drive chain case on my G3 (engine 1956, AMC gearbox): the gap between the gearbox sprocket and the chain case is quite narrow. There isn’t sufficient clearance for the rear chain – the rear chain massively touches/scratches the back of the chain case. When I put the spring clip (chain connection link) in, I can rotate the sprocket a little bit until the whole thing locks up. I removed the front half of the chain case and found that there is enough room between the inner side of the back half and the clutch body allowing to move the back half further outwards. But would this be the correct way to solve the problem? Or are there different variants of the back half (I found two part nos 022237 and 022575, MS and MCT/MCS respectively).
I am a bit lost on what to do next. What do you think and recommend …?
Thank you very much. Regards, Peter
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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby Pharisee » Tue Dec 11, 2018 11:21 am

I had the same problem when I put together my G3L basket case. I think that over the years and with a few different owners, the chain case had become a little distorted. The rear half mating face didn't match the front half particularly well, either. Subtle adjustment with a hammer sorted it.

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby clive » Tue Dec 11, 2018 2:06 pm

Could be the wrong size spacer behind the inner chaincase (between that and the engine plate). As you do up the stud that would pull the whole case across too far at the back as tge front is fixed.
clive
if it ain't broke don't fix

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby Expat » Tue Dec 11, 2018 2:57 pm

Pharisee wrote: Subtle adjustment with a hammer sorted it.


Surely you mean ‘tapometer’ ?

:)
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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby oldandsmelly » Tue Dec 11, 2018 5:13 pm

I had the same problem when putting my G80 together. Mine wasn't so bad that the chain locked but it made a nasty scratchy clunky noise as the back wheel was rotated. You can gain a few thou extra clearance by having the split link fitted on the gearbox side of the chain but that won't help here I suspect.

I tried extra washers behind the centre spacer but that caused problems with the chain rubbing somewhere else.

In the end, I fitted the back chaincase and pulled it out hard until it stopped rubbing. Not a pretty solution, but it worked and the chaincase doesn't leak oil afterwards.

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby Duncan » Tue Dec 11, 2018 5:44 pm

I believe that there is a different rear pressed steel chaincase for the AMC gearbox, 1957 only as the alloy case was introduced in 1958.

Edit:

Strike that statement, Twins are different but road singles both list 022237 for 1956 and 1957

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby raffles » Tue Dec 11, 2018 7:05 pm

It could just be the thickness of the side plates on the chain. The original chain would have been Reynolds 5/8": 3/8".
Some of the metric and the American chains although they match in size and will fit, have much thicker side plates and
of course longer link connectors making the whole chain wider on the outside overall thickness. I have had this problem
a couple of times and fitting the correct chain solved it
Tony

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby tippi11 » Tue Dec 11, 2018 9:55 pm

Tony, can you please provide the name/source where you bought the correct chain (just in case I cant get this Reynolds one over here in Germany...).
I already tried a chain other than the one shown on the images. It was a DID Japan, also 5/8 x 3/8, but this had even thicker side plates - the result was worse, worse ... immediate lock-up.
Thank you. Regards, Peter

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Re: G3 - Insufficient gap between chaincase and gearbox spro

Postby tippi11 » Tue Dec 11, 2018 10:14 pm

Tony, is it Reynolds or Renold?
Regards, Peter

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