So my piston got chewed up on the front by the exhaust port looking like a lean condition occurred. Before pulling off the cylinder I did a leak down to see if it was pulling air from somewhere else and it held pressure fairly well. When it quit I was in some tall grass riding the power band in 4th or 5th gear, so under a good amount of load. The fuel tank was also running very low. When I got home I pulled off the line and it only had an ounce or two of fuel left in the on position. Could it have blown because I was riding it too hard while it was running out of fuel?
Blown topend.. Thoughts?
- Thread starter N2oExpresS2k
- Start date
i vote you've figured out how it blew....
high rpms under load while starving it for the fuel needed to cool it and oil needed for lubrication, while still providing it a wide open throttle full of air = boom
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This sounds like it could have helped as well, small air leak + fuel starvation= BOOM. 2 strokes must be airtight, period.....
Gotta be sure I know what killed it before I go out again. Thanks for confirming guys.
I'm running a 330 jet with a CPI BB pipe. Piston was a 67.5 wiseco. Looked like it was running rich when I checked the plug..
Just how long did it hold 7psi for?
What plug did you use for the plug chop?
Not terribly long, but much longer than it did when I tested the first time. Probably about a minute or so. I know that's not ideal but that's also why i'm running a pretty big jet for my mods (cpi pipe w/ no lid).
br8es
The air leak would have been the main contributor to the problem.
Compensating for an air leak with a larger main jet just does not work, as the motor would have been running a lean mixture over the full range of throttle opening.
Everything up to 3/4 throttle would have been affected, as the main jet only comes into play at between 3/4 to WOT.
The motor will perform extremly well with a slightly leaner mixture, but will slowly but surely eat the top of the piston close to the exhaust port.
The straw that broke the camels back and finally killed the piston would have been the intermittant, very lean mixture delivered as the carby ran out of gas.
Compensating for an air leak with a larger main jet just does not work, as the motor would have been running a lean mixture over the full range of throttle opening.
Everything up to 3/4 throttle would have been affected, as the main jet only comes into play at between 3/4 to WOT.
The motor will perform extremly well with a slightly leaner mixture, but will slowly but surely eat the top of the piston close to the exhaust port.
The straw that broke the camels back and finally killed the piston would have been the intermittant, very lean mixture delivered as the carby ran out of gas.
Wiseco piston huh? Could you please post a few pictures of the piston? Do you warm up the engine before riding?
my edu. guess as well only shorter
lean mix. and not a filled tank will starve the motor of it's precious coolant the gas and oil mixture my friend
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