Clashing valves

Information relating to the Matchless G9 or AJS Model 20 500cc twin
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john kitchen
Posts: 42
Joined: Tue Dec 10, 2002 12:00 am
Location: PETERBOROUGH UK

Clashing valves

Post by john kitchen »

The valves of my 1960 G9 have been getting far too intimate with the pistons. I thought at first that I had the wrong pistons but having seen the earlier domed pistons I am less sure. My pistons are flat tops.
Any ideas why the contact?
Where there different flat tops fitted?
Getting desperate now, Yamaha`s starting to appeal.

JK
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bjork
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Posts: 1905
Joined: Wed Jan 01, 1997 12:00 am
Location: LEICESTERSHIRE UK
Location: Leicestershire

Clashing valves

Post by bjork »

have you checked the valve timing?assuming the pistons are meant for this engine,flat tops should be nowhere near the valves.Are all the valves touching or just one pair or a single valve?I'm thinking along the lines of a sticking valve stem perhaps.Have you been running this engine for a while or is it just built?
Using yesterdays technology to create tomorrows problems today
john kitchen
Posts: 42
Joined: Tue Dec 10, 2002 12:00 am
Location: PETERBOROUGH UK

Clashing valves

Post by john kitchen »

steve,
I have only owened the bike for a couple of months and know little of its history.
The valves that are clashing are the two inlets and the valve timing was OK.
The pistons for the pre-60 G9 are domed and mine as you know I described as flat topped, though they would be better described as slightly domed.
I am unsure as to if these are the correct pistons but I am having trouble getting any information on the correct pistons.

Regards

John
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bjork
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Posts: 1905
Joined: Wed Jan 01, 1997 12:00 am
Location: LEICESTERSHIRE UK
Location: Leicestershire

Clashing valves

Post by bjork »

as it's both inlets touching,I would want to check the inlet cam timing with a degree disc,rather than rely on the timing marks alone.hope you get it sorted,it's always a bit of a lottery with a 'new' bike.I always seem to end up completely rebuilding everything I buy,and I'm not THAT fussy! I think?
Using yesterdays technology to create tomorrows problems today
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