piston diognoses please

srxeater

srxeater

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Joined
Jan 29, 2008
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119
Age
40
Location
Neillsville, Wisconsin
what are your thoughts on this piston failure? the other 2 pistons were washed clean so i dont think it was a jetting issue. i've never seen a hole melted in the side like this. also there is scoring on all 4 corners, and its hard to tell but the ceter of the top is gouged out a little.
 

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Mine looked a lot like that when I didn't have any coolent in the sled!!!!! Someone else should chime in !!!!!!
 
One thing is for certain, you heated the whole piston up which takes a little time. Coolant may have been the problem. What does the plug look like?
 
i got this thing with the cyl. already removed, plugs were mia. i think it was ran for a while with the roached cyl. the head is all beat to hell.
 
jetting appears to have been really lean. air leak somewhere maybe. also, there was some deto occuring. your exhaust gas was so hot, that it started to erode away the edge of the piston crown on the exhaust side and melt that hole thru the piston skirt. my boss melted a hole like that in the side of his piston on his polaris, and it was lean jetting and air leaks which caused it.
 
i was just inspecting the crank seal. it looks smeared and there is rubber on the crank where the seal rides. looks to be the cause of this. its the pto side piston by the way.
 
ive seen water due this it half freezes shut a main jet and then its to late.Lately in new brunswick we have been getting alot of water in our fuel ive had to replace my water seperator twice all ready but it still beats a meltdown
 
How was the power valve I saw a similiar thing with a piston last year and the valve was stuck.
 
I suspect there is very little left of this engine to salvage...don't forget the metal in the carbs pumped through the boost bottle kit through the destroyed reed cages attached to the damaged crankcases by the now overheated and out of phase crankshaft!!! ...Yes I have been there on a Big Bore 800cc Mod SX...TWICE!!!
When you start over, put an airbox on it and keep the compression ratio down. My now trail mod 700cc SX runs on premium fuel all day and still beats any "stock" SRX.
 
mine looked like that ,what happened to mine is ring keeper pin broke and ring turned until it found port and BOOM broke chunk out of top of piston mine was at low speed and when i felt it i stopped right away that one looks like it was ran for awhile
 
this it not from my modded sx witch has 2700 trouble free miles on my current setup, its from a mildly ported srx with airbox and no boost bottle. the reeds and cases are perfect. the only damage to the crank was from neglect of the previous owner taking the jug off, and letting it sit for 3 months with coolant in the bottom of the case.
 
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