Where do I go, where do I go, where do I go now?

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Joker_Bones
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Re: Where do I go, where do I go, where do I go now?

Post by Joker_Bones »

Way to Go!
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spookefoote1956
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Re: Where do I go, where do I go, where do I go now?

Post by spookefoote1956 »

Here's an update. Started tuning and she didn't want to start, not with the same reliability. Put the fuel tank back on with fresh fuel and still wouldn't start with any desirable frequency. Reset carb and cleaned. Checked timing. Spot on. Valves fine, pushrods rotating at tdc. Points gap fine. Plug gap fine. Occasional firing but with no regularity. Goes bang fully advanced. Checked the compression 90psi ooer. Put a bit of oil in the barrel went up to 120psi. OMG had I damaged a ring when rebuilding. Took the head and barrel off. No damage to the cylinder, piston or rings.

I'm off to buy an Ariel3!
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
SPRIDDLER
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Re: Where do I go, where do I go, where do I go now?

Post by SPRIDDLER »

spookefoote1956 wrote: Sun Sep 04, 2022 4:12 pm Reset carb and cleaned. Checked timing. Spot on. Valves fine, pushrods rotating at tdc. Points gap fine. Plug gap fine. Occasional firing but with no regularity. ...........

I'm off to buy an Ariel3!
You read my mind, Spooky.

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spookefoote1956
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Re: Where do I go, where do I go, where do I go now?

Post by spookefoote1956 »

Forgot to add. I did a spark test with the plug tip cut off. Great spark. The mag is a reconditioned one from the club spares.
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
Andy51
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Re: Where do I go, where do I go, where do I go now?

Post by Andy51 »

I have had a JP 8.5 to 1 piston in my 18S for some years and it has never given me any problems. I have recently had lack of compression on the bike after a long lay-up and top end rebuild, but a fellow club member came round with his paddock starter (thanks, Roger!), spun the motor, indentified timing was out, put the timing right and spun it again, started instantly and compression returned. The rings must have been 'glued' in their grooves by old oil and just needed a quick blast to loosen them off and return to normal compression. I assume you have taken your barrel off and looked at the rings, were they fully free in their grooves? Andy
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spookefoote1956
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Re: Where do I go, where do I go, where do I go now?

Post by spookefoote1956 »

Thanks for that Andy. Food for thought
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
Cupoftee
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Re: Where do I go, where do I go, where do I go now?

Post by Cupoftee »

Have you a decent carb on the bike?
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spookefoote1956
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Re: Where do I go, where do I go, where do I go now?

Post by spookefoote1956 »

Hello again. Sorry for the late reply Cupoftee. I've been away and all manner of diversions have taken place. The carb is a "new" Amal 389, set up by Surrey Cycles. Worked fine for the past three years.

The stage I am at is that the Beast fires but not with reliable regularity. Sometimes by kicking over with the decompressor in to get momentum then dropping it; sometimes giving it the boot. However, this does not happen reliably enough to go for a razz. To my mind it is now carb related. I will do another compression test just to confirm that everything is ok. Can't see why it shouldn't be.
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
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spookefoote1956
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Re: Where do I go, where do I go, where do I go now?

Post by spookefoote1956 »

Just tested again. Between 90 - 100 psi depending on the boot. Throttle wide open.
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
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Taid
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Re: Where do I go, where do I go, where do I go now?

Post by Taid »

Are you sure ignition insulation isn't breaking down when trying to fire the plug at high pressureswe .. in RAF plug bay we had a plug tester where we could increase the pressure and see what pressure the plug failed at .. below a set value, plug was scrap .. if you could get an oscilloscope that can take high voltage you can see if the plug fails to fire ..

I
___

Now sold ... 1956 AJS 16MS Bitsa .. HSU 414 .. rebuilt/re-registered 1987
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