1959 G3C ('62 Shortstoke Engine) cam problems

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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1959 G3C ('62 Shortstoke Engine) cam problems

Postby Peter Morris » Sat Dec 29, 2018 6:18 pm

Hi All,

So deciding to go over the ign timing on my G3C, I removed the magneto chain cover to find quite a lot of oil in there. It is obvious where it is coming from, around the exhaust cam.

I removed the cam to find it it quite worn (mainly between the arrows in the picture) on the the shaft as is the outer bush. When the cam is inserted into the bush it rattles around a lot. Obviously the bush needs replacing, and although I have not checked it yet, I would think the inner bush needs changing too.

Question 1: Is it possible to remove and fit a new inner bush without removing/dismantling the engine?

The cam is quite worn so I am guessing I will have to get it ground and get an oversize outer bush made, unless anyone can recognise the cam....

Problem is mainly that the engine has been built from a 1962 short stroke roadster (model 16) bottom end that has an alloy barrel fitted, so I'm not sure if it's a road cam or a comp cam..... nor if the cam is available anywhere.

The engine has a magneto, which the roadster short stroke 350's obviously didn't have, so I am guessing a comp cam?

I have someone that can take a bit off of the cam's shaft/make oversize (undersize?) bushes if necessary but I'd rather buy a new cam/bushes if they are available.

Thanks
Peter

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Last edited by Peter Morris on Sun Dec 30, 2018 8:50 am, edited 1 time in total.

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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby ajscomboman » Sat Dec 29, 2018 7:06 pm

You can replace the spindle in all AMC cams but they're bloody tight. Best thing to do is pick up the phone and have a chat with Ken De Groome he'll tell you everything you need or don't want to know.

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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby Reynard24 » Sat Dec 29, 2018 9:42 pm

Rob's right - Ken has just sorted an incredibly bodged '63 short stroke for me. He's very knowledgeable and a very nice guy to deal with.

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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby Peter Morris » Sun Dec 30, 2018 11:46 am

Thanks for your replies Rob/James, I was hoping that someone could recognise what cam it was so I could try to find one (very difficult when you don't know what you are looking for 😂)
Also would like to know if the inner bush can be changed without major disassembly.

I recalled that when I first started/ran the bike after it's rebuild, the magneto armature was bent so that has maybe done for the cam.

I'll pop a better picture of it on in a while.

Peter

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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby clanger9 » Sun Dec 30, 2018 12:07 pm

There's a nice Ken De Groome article on the archives that might help. It has some good pictures of the various cam types...
http://archives.jampot.dk/technical/Gen ... e_Dots.pdf
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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby SPRIDDLER » Sun Dec 30, 2018 1:11 pm

Peter, just as an aside, the inner bush has (should have) an anti-clock scroll cut into it in order to 'screw' the oil back into the timing chest. If this wears then oil can/will migrate along the cam axle, up the mag chain and worst case get into the mag. Some years ago I replaced that bush and I later discovered that the scroll had been incorrectly cut clockwise which actually drew oil along the axle and it fair poured out of the mag chain cover. You can't change the orientation of the scroll by turning the bush around end for end ;) I split th'engine again to replace it. :(
I doubt that it can be replaced without splitting the c/case halves as the inner end of the bush is so close to the flywheel that there isn't room for a puller or drawbolt with lips etc. You might be able to remove it with a slider extractor (a rod with the end turned up a bit) but if the turned up tip breaks off it'll drop inside the c/case. I have wondered about using a Rawlbolt to act as a puller by expanding it inside the bush but that might just expand the bush making it grip the c/case casting even tighter................ :?
Last edited by SPRIDDLER on Sun Dec 30, 2018 1:19 pm, edited 3 times in total.
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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby ajscomboman » Sun Dec 30, 2018 1:16 pm

Peter Morris wrote:Thanks for your replies Rob/James, I was hoping that someone could recognise what cam it was so I could try to find one (very difficult when you don't know what you are looking for 😂)
Also would like to know if the inner bush can be changed without major disassembly.

I recalled that when I first started/ran the bike after it's rebuild, the magneto armature was bent so that has maybe done for the cam.

I'll pop a better picture of it on in a while.

Peter


That's why I suggested calling Ken. Anyway I suspect that the cam is a bog standard lift cam from 52-53 (it's possible it's earlier but without knowing the lift I can't be certain) as it's only stamped 1&2, later HL cams are stamped 1, 2 and 3. Scrambles cams are marked SH. As for the inner bush, very difficult in situ and not really recommended. The inner bush should be scrolled to stop oil from entering the timing cover. The outer bushes are easily swapped by heating the case and pressing out and the same again for installation.

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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby G15 Roy » Sun Dec 30, 2018 2:34 pm

clanger9 wrote:There's a nice Ken De Groome article on the archives that might help. It has some good pictures of the various cam types...
http://archives.jampot.dk/technical/Gen ... e_Dots.pdf


it is now also on the clubs tech Singles pages. http://www.jampot.com/article_read.asp?id=652
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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby Peter Morris » Sun Dec 30, 2018 5:29 pm

Thanks for the all the replies guys, here is the better picture I mentioned earlier.

Not a great one for phoning people for help especially if I've not met them, but I'll see how I get on and call Mr De Groome if I have to.

Nev, Only idea I can think of re inner bush removal in situ is heating the case around the inner bush and using a large easy out screw extractor (with the sharp end cut off to suit)...... not sure what I'd use to grip the easy out with though 😂😂
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Re: 1959 G3C ('62 Shortstoke Engine) cam problems

Postby g80csp11 » Sun Dec 30, 2018 6:35 pm

Peter check out if a raw bolt will fit , it expands out to grip the bush and then you can draw out . you will still need to warm the crankcase

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