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[Tim Hurst]

Hi
Need help with my son's '01 500 bullet. After a long ride to the peak District the bike eventually stopped. A white plug and the bike acted like the decompression lever was being used when he tried kicking it over. would a leaky decompression valve cause this (or cylinder head gasket??)
Any help as ever greatly appreciated

[ric]

Tight exhaust push rod.

[PeteF]

Yes, a leak at the decompressor would do it. You'd likely hear it wheezing into the exhaust port.
If the head gasket had blown it would be pretty obvious by the mass. Also, as Ric says, tight pushrod would hold a valve open.
The white plug is concerning, I'd get to the bottom of that. Ignition timing? carb tune?

[Tim Hurst]

yeah probably carb, he said there was a bit of fuel weepage when he turned the bike off.(don't worry dad its fine, Kids!!). The other 2 seem a reasonably easy check. Thanks both.

[Beezabryan]

Leaky decompressor valve is very unlikely.
First check exhaust valve clearance. If it has tightened up there may be valve seat recession. If clearance OK then I'd pull off the head & barrel to check piston for damage. White plug is ominous, carburation would be the next job after after sorting the lack of compression

[Beezabryan]

On further thought, not valve seat recession. White plug, burnt exhaust valve & seat?