normalario Posted November 20, 2003 Report Posted November 20, 2003 Just smoked a piston and I am pretty sure it wasn't a carburetion issue. Burned a whole right through the top on one cylinder. Could the culprit be faulty reeds? How would I go about testing my bottom end for leaks? Thanks! Quote
Patriot Racing Posted November 20, 2003 Report Posted November 20, 2003 Could have been old/bad fuel....sounds like a solid case of detonation.... Are you sure it couldnt be a carburation issue? A clogged main jet can send things south in a hurry! Quote
boonman Posted November 20, 2003 Report Posted November 20, 2003 Improper squish, too low of octane, (like bad/old fuel as suggested), too much advance on the timing, or a combination of things. But, a hole in the piston is almost a dead giveaway that some sort of detonation was going on. A clogged main jet, can add heat to the problem, and accelerate it's showing, but I don't think a clogged main would blow a hole on it's own. What was your squish set up at? Timing? What other mods are done to it? Quote
normalario Posted November 21, 2003 Author Report Posted November 21, 2003 Filled up with fresh 91 before I ran her. Engine was about 9 pounds off on the cylinder that went but I figured I could get on more weekend on it before a rebuild. Ran great at the hill but crapped out on the way back to camp. The head work was done by D&M. Mill, re chamber, & correct squish. Ran good for a season on the new head. How do I check my timing? Thanks again! Quote
boonman Posted November 21, 2003 Report Posted November 21, 2003 You could check it with a timing light, but I am not sure where the marks are.... Quote
Banchetta Posted November 22, 2003 Report Posted November 22, 2003 What did D&M set the head mods for??? 90 octane?? 93octane??? 100 octane?? Too much compression and not enough octane and walla!!! That would be my first guess.....Your timing would be stock unless you put a timing key or adjustable timing plate in.... Quote
normalario Posted November 23, 2003 Author Report Posted November 23, 2003 I am pretty sure it was set for 92. I ran it for a whole season problem free. Will be running 100% 110 on the rebuild. I assume the timing has been adjusted with all the other mods. Can timing go out of adjustment?? Quote
boonman Posted November 24, 2003 Report Posted November 24, 2003 Can timing go out of adjustment?? Not unless you shear the key or the timing plate has been modded and it comes loose. Or a faulty CDI, but I have never heard of the latter causing improper timing, only a dead CDI... I am thinking that you had slightly lean jetting, and this heated up the situation, and made an improperly set up head design show it's ugly face... Quote
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