piston problems

vintage srx

vintage srx

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Joined
Sep 3, 2007
Messages
91
Location
harrow ontario
I was cleaning power valves in my brothers 01 srx and i was looking threw the power valve port with a flashlight. This is what i found in the center cylinder.What do you think caused this .
 

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This past summer we did change the reed peddles did find one bad i think it was the middle cyl.The thermostat also was in pieces replaced it .But she ran fine and strong all last winter no cyl damage.Just the top of the piston was damaged head was also fine.We already fixed it,all new rings and 1 piston.
 
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Definitely was leaned out at some time,a piece of dirt in the main jet or a little ice?Hard to say but it's good that you caught it before any further damage was done,whenever I had a piston go as a result off a lean burn down it always took the cylinder with it and once or twice the head got banged up.
 
better find the problem, just replacing the parts it will happen again. Check the carbs over good, that center one anyway. I once rode with a guy that kept burning down over & over, just kept rebuilding it, never found the problem & corrected it. He no longer has that sled.
 
snomofo said:
Looks like lean burn down (fuel delivery or unmetered air), not detonation.
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I know what it looks like yea but if it's a srx(waz held to the bar i bet) there was detonation from the 87 i bet he was using.
 
Yes i did check everthing over carbs are also clean, boots are good.Just a bad reed pedal and thermostat.Yes he did run 91 but you never know what you are actualy geting.
 
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modsrx said:
make sure he run the right jetting ,and needle clip
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150 main pto, 148.8 center and mag, w/clip in middle position and both washers underneath, and 42.5 pilots and fuel screws @ 1-1/4. this jetting is for a stock unmodded engine.
 
i would say that its detination posibly from that cylinder running hotter with borderline fuel just my opinion
 
just a point of interest, but if you hadn't cleaned the piston before taking the pics people could try to help read the piston wash, cleaning it removed any evidence of how your jetting was
 
Hey if you can't find anything wrong on the intake side then make SURE you have NO EXHAUST leaks.

Exhaust system is just as important as proper carburetion on a two stroke, if there are leaks it will run lean for sure.

Also, it was not you thermostat as a bad thermostat would cause the engine to run cold and probably the scoring would be on the intake side in the case.

Hope this helps.
 
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