black sunshine Posted June 22, 2011 Report Share Posted June 22, 2011 (edited) http://rides.webshots.com/photo/2336150050104901534HbxeQj What do you think would cause this after 2 seasons of riding with no compression loss? The only clue I have is the fire went out in that cylinder a few sporadic times before this happened. I also did a leakdown test before dismantling and found that side's carb top was leaking. Was also told that gas went to shit and it finally caught up with my 160psi +4 timing motor on pump gas. You can still see the crosshatch in the good cylinder and that side never lost a single pound of compression. let's have it!!! Edited June 22, 2011 by black sunshine Quote Link to comment Share on other sites More sharing options...
coryv4 Posted June 22, 2011 Report Share Posted June 22, 2011 i dont really think it was gas i cant see any sign of pre det. it seems like it was running lean and melted the piston maybe the air leak caused the lean condition also what do your plugs look like? Quote Link to comment Share on other sites More sharing options...
banshee_R1 Posted June 22, 2011 Report Share Posted June 22, 2011 X2= way lean the piston is spotless. Looks to me like your lucky though.... could have been alot worse!! Quote Link to comment Share on other sites More sharing options...
crash&burn Posted June 23, 2011 Report Share Posted June 23, 2011 Air leak on the damaged side. If it was fuel i would have thought to see the other piston damaged as well. Quote Link to comment Share on other sites More sharing options...
camatv Posted June 23, 2011 Report Share Posted June 23, 2011 big time lean out. maybe you ran it down a road topped out and it fuel starved on that side or got some shit in t he main.. OOPS!! that had to have sounded really bad Quote Link to comment Share on other sites More sharing options...
black sunshine Posted June 23, 2011 Author Report Share Posted June 23, 2011 big time lean out. maybe you ran it down a road topped out and it fuel starved on that side or got some shit in t he main.. OOPS!! that had to have sounded really bad Well, I wasn't riding it at the time so I don't know what it sounded like! Was on my 250 that wasn't running worth shit (turned out to be a plugged gas cap vent), my girlfriend was on the banshee for the first time. She was having trouble keeping it running. Checked the plug on that side and it looked fine, not fouled. Threw my buddy on it as we hit a long stretch of gravel road. I went back to camp to get a spare motorbike, by the time I got there he was calling me to say she was locked up. He then "got it running" again when I showed up. Looked at the plug and it was silver. I should have known something was up with the sporadic smoke out of that sides pipe. I was just so disappointed at the 250 and the fact we were going on a 100 mile ride and I was holding everyone up, looking like a jackass. Checked the carbs, never found any blockage or crud, the only thing weird was the leaking carb top on that side. I remember Dagejr(sp) saying that could fuck a motor up, but no one else seems to agree. Everyone seems to think too much compression and timing for the current gas at the pumps. I thought the other side would have shown some ill effects if that was the case. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted June 23, 2011 Report Share Posted June 23, 2011 if you blow up the picture you can kind of see what looks to be small pitting on the piston from detonation.....does it look like that up close in person or am i just seeing things black sunshine? if it were bad fuel i'd expect to see it on both sides......and i agree....it went WAY lean. The carb cap was leaking? how did you plug the carbs to do a leak down with the carbs on? i've NEVER done a leakdown with the carbs on. You said you checked that plug to see if you had anything wrong with it.....are you sure you didnt have a fouled plug and by mistake created a leak with the spark plug? either that or your buddy had it pinned wide open for a LONG time and the jetting may have been a tad lean on top.....causing it to lean out and melt through the piston. what was your jetting on the bike? Quote Link to comment Share on other sites More sharing options...
FASTOYS Posted June 23, 2011 Report Share Posted June 23, 2011 "Long stretch of gravel road" ...... hole in piston = DEFINETLY ran low on fuel and leaned it out!! (Right side usually goes first in this situtation) Send them back to us and i will hone them for free if needed and get you going. Quote Link to comment Share on other sites More sharing options...
black sunshine Posted June 23, 2011 Author Report Share Posted June 23, 2011 "Long stretch of gravel road" ...... hole in piston = DEFINETLY ran low on fuel and leaned it out!! (Right side usually goes first in this situtation) Send them back to us and i will hone them for free if needed and get you going. Already had them bored locally, thanks anyways, Jeff. Actually cleaned up the cylinder with some muriatic, then bought a 4 mil crank and had to get them bored to fit the pistons cause they don't make one for .010"!! The slag ate up the crank bearings. I guess what was really puzzling me is that side was intermittently working correctly at different throttle positions, including idle. I just didn't take it seriously because the thing was so bulletproof. Must have had a blockage of some sort in the jets. I was running 380 mains, 27.5 pilots. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted June 24, 2011 Report Share Posted June 24, 2011 If running stock carbs, that was enough main jet, so I would say that carb was starved of fuel. Maybe time to gut that gas cap and get a pingel dual outlet fuel valve? Quote Link to comment Share on other sites More sharing options...
coryv4 Posted June 25, 2011 Report Share Posted June 25, 2011 i had a problem with my stock gas cap getting plugged and starving it of fuel past half throttle Quote Link to comment Share on other sites More sharing options...
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