G80CS timing... with 600 crank?

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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G80CS timing... with 600 crank?

Postby Braaap » Mon Jul 16, 2018 8:33 pm

I posted recently re spares availability for G80CS.
Well i've bought the bike 😊

Turns out it has a 600 crank in it... but due to the engine shop making a hash of boring the cylinder... it has been put back to a standard 86mm piston with a new barrel. (89mm for 600).
Does anyone have timing and mag setting info for a 600 single... and for the BTH Mag please?
The 600 has 96mm stroke. I need to know the degrees of full advance... i can calculate the distance

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Re: G80CS timing... with 600 crank?

Postby Braaap » Mon Jul 16, 2018 9:03 pm

Calcs suggest about 560cc.

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Re: G80CS timing... with 600 crank?

Postby SPRIDDLER » Wed Jul 18, 2018 4:02 pm

Edit.
If you haven't seen them these articles may be of interest. No ign timing info though.
http://archives.jampot.dk/editorial/Scr ... ne_Feb.pdf

another one here

http://archives.jampot.dk/editorial/Scr ... l_1959.pdf

EDIT:
The second link doesn't seem to work so you can view both of those above and other stuff from the index here:

http://archives.jampot.dk/editorial/Scramblers/
I poke badgers with spoons.

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Re: G80CS timing... with 600 crank?

Postby Braaap » Thu Jul 19, 2018 2:37 am

Thanks Chap. I read the first one earlier.
I'm in NZ. Some tuning info would be handy ☺

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Re: G80CS timing... with 600 crank?

Postby SPRIDDLER » Thu Jul 19, 2018 7:14 am

Stuart.
I've been in contact with a pal in U.K. who has a Typhoon (and rides it ;) ) among his collection of AMC bikes. He has suggested that you contact him direct as he has 'some bits and pieces of information that may help'.
I don't want to disclose his email address in public and since you are not a subscribing member I cannot send you a private message so have emailed it to you.
Sprid.
I poke badgers with spoons.

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Re: G80CS timing... with 600 crank?

Postby Braaap » Sat Jul 21, 2018 9:37 pm

Advice from the experienced Typhoon owner: Time at 7/16" BTDC.
See how she goes

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Re: G80CS timing... with 600 crank?

Postby mdt-son » Wed Aug 08, 2018 7:48 am

Braaap wrote:I posted recently re spares availability for G80CS.
Well i've bought the bike 😊

Turns out it has a 600 crank in it... but due to the engine shop making a hash of boring the cylinder... it has been put back to a standard 86mm piston with a new barrel. (89mm for 600).
Does anyone have timing and mag setting info for a 600 single... and for the BTH Mag please?
The 600 has 96mm stroke. I need to know the degrees of full advance... i can calculate the distance


So you've got a long stroke G80CS ... :-) What kind of piston is fitted?? None of the standard pistons will fit (C/R will be way too high due to the combo short barrel & long throw). Actually I suspect your combo will not mate up at all unless you revert to the proper crankshaft.

You are probably aware of the fact that new 500 crankshafts are available from Australia? I got mine from Ken deGroome years ago (nicely made out of EN32) and he may be able to serve you.
ABSAF also makes them. Since the same conrod was used for 500 & 600 engines, all you need is a pair of new flywheels.

-Knut

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Re: G80CS timing... with 600 crank?

Postby Braaap » Tue Aug 14, 2018 11:41 pm

It has a spacer under th barrel to get th long throw crank working
600 crank is even longer stroke than the longstroke 500... my calcs suggest 560cc.
Piston is rumoured to be a JP

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Re: G80CS timing... with 600 crank?

Postby Braaap » Wed Aug 15, 2018 6:06 am

There is an oil leak from the head/barrel pushrod area, and has a gasket fitted ( should be metal to metal ), so i will be pulling the head off.
I will have a measure up then.
Piston is standard size with new barrel bought when it was fitted... but what standard size... 86 or 82.5 ?
I do know the stroke @ 96mm

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Re: G80CS timing... with 600 crank?

Postby Braaap » Wed Aug 15, 2018 6:49 am

I have just had a look at th spacer under barrel. 3mm.
Therefore it has a long stroke barrel CS barrel. For 513cc.
An extra-long stroke G80CS ☺

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