- Location
- New Jersey
Sucks, trying to figure out what happened. 93octane and 50:1 Premix, had been riding great all week long until this!
Fx1 motor blew up!
- Thread starter Stavissimo
- Start date
- Location
- Granbury, TX
I'll go out on a limb and say you went lean. There's no visible piston wash... Check your carb filter and your fuel filter. You might have also sucked air through a fuel selector or primer. Also check your crank seals. What was your jetting?
- Location
- New Jersey
very low hrs on the motor, fogging every season. Have always changed the fuel filter but not carb filter actually. Fuel selector was deleted but I do have a primer hooked up. Always give it a few pumps on a cold start and let it warm up. Not sure of jetting will report back
Myself
manic mechanic
- Location
- Twin Lakes AR
That's from water ingestion. Probably a leaky head or base gasket.
- Location
- New Jersey
Damn really? Thanks for the info!
- Location
- Granbury, TX
Wouldn't the piston tops be a bit cleaner? No trying to argue, but to learn. What's your reasoning?
- Location
- Charlotte, NC
What's the other piston look like?
- Location
- New Jersey
Myself
manic mechanic
- Location
- Twin Lakes AR
LOTS of water ingestion/intrusion will steam clean the piston top and dome, and keep all the lube washed off the piston so that it scores and usually locks up. A little bit at a time leaves that sludgy grey substance you see on the piston. All the while causing detonation and eating away at the squish area of the piston as you see on this one. I'd also like to see a bit more wash on that other piston. Not lean enough to damage things but a little fatter sure wouldn't hurt.
- Location
- Long Beach, CA
Single carb and one bad piston would at least rule out the carb. Has the idle changed lately? Could be be a bad crank seal. My piston had been getting washed now for the whole year and found one dome wore a ridge in the head shell allowing the Oring to lift off the cylinder shooting water in at higher speeds but never caused what happened to yours. The things that I've had that caused detonation (pits on the exhaust side of the piston) have been bad crank seals and too much compression.
- Location
- Charlotte, NC
This is why you always do a leakdown before you disassemble the engine after it blows up. Now you're just guessing as to if you had an air leak at this point. The other piston honestly looks lean to me. It's easy to.not think about the leakdown after you drop a cylinder. When it happens you can hear it down a cylinder.. at that point it's best to get it home where you can do a proper leakdown before teardown. I always do a leakdown after rebuild as well.