Maintenance & Technical > KX500 Original
suddenly too rich
tschisi:
~100psi, again.
Leakdown test:
The engine holds the under pressure rather good, but when i wiggle the flywheel it decreases faster.
Splitting...
btw, a ktm 144sx piston works nice for sealing the k5?s exhaust port :wink:
Goat:
With a new plating on the cylinder I wouldn't run that old piston. It has already been formed for the old plating and wont have the right clearance all the way around. probably egg shaped and causing some of your compression issues. It's best to use a new piston & rings with new cylinder plating.
tschisi:
Sure a new piston would be better, the old one is just for testing.
But i don?t think the old piston could cause my compression problem when coating and rings are new?!
I?m also afraid the seal isn?t the solution, because when i did the compression test i put a large amount of grease on the seal so it couldn?t suck (much) air.
It didn?t make any difference... :?
Motorrad:
--- Quote from: tschisi on January 22, 2011, 07:10:05 PM ---Sure a new piston would be better, the old one is just for testing.
But i don?t think the old piston could cause my compression problem when coating and rings are new?!
I?m also afraid the seal isn?t the solution, because when i did the compression test i put a large amount of grease on the seal so it couldn?t suck (much) air.
It didn?t make any difference... :?
--- End quote ---
Curious... whats your ring end gap?
are you sure the ring lands were clean? free of burs? proper spec? this could cause a re-occuring issue when using the old piston...
tschisi:
I haven?t measured the gap, can do this when i have dismantled the engine again.
I?m not planning to run the engine long with the old piston, but it has to run first...
Is it maybe possible that the 100psi are standard for not broken in coating and rings?
Guess i still won?t be able to start the engine with that value...
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