Maintenance & Technical > KX500 Original

blown up any ideas

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holeshot buddy:
riding my af500 last week in a race
locked up on second corner and spat me off
took it home pulled off barrel
piston disintergrated not even on rod
bore gouged conrod bent  (not happy)
engine about 30 hours old genuine piston
no power valve damage
looks like piston has  maybe cracked through gudgeon boss
and broke off a big piece which made a mess
no warning no noise no pinging
no coolant loss etc
anyone struck this i have been racing kx500s for 25 years
never done this
running at 32 to 1 motul 800
any ideas

BDI:
I have seen stock cast KX500 pistons with cracks in the skirt at twenty hours. Cast pistons should be replaced once a season or every twenty hours as preventive maintenance. You got lucky the rod didn't come out the bottom of the cases.

stewart:
cast dont last

oic0:
Yikes, cast pistons really go to pieces don't they!

Differen't bike, but I broke a piston in an RD engine. It was a forged wiseco. The guy who ported it went to big on the intake and the piston could rock and hit the bottom of its skirt on the bottom of the intake. The piston broke the bottom of the sleeve and cylinder off. Didn't shatter though, it bent and had one crack at the base of the windows (it was a banshee piston with two big windows cut into it). Completely destroyed my cylinder though :(. I have much faith in the strength of wiseceo pistons now though! the stinkin thin windowed skirt broke my cylinder to pieces without sustaining all that much damage its self.
I was thinking about trying cast but not after seeing that!

kxraptor:
Never seen a piston fragment  so much.

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