Jaystre Posted June 1, 2010 Report Share Posted June 1, 2010 hey i just blew a piston on the right side a first i thought it was a plug because it was only running on one cylinder so i shut it down and unscrewed the right plug first and it was white . put my thumb on the hole and crank it over by hand to see if the compression was there and on the second crank it wouldnt turn no more . so ill be taking it apart very soon to see what happened in there . what could of cause one cylinder to be running very lean . ill keep you up to date when i tear it down . thx in advance Quote Link to comment Share on other sites More sharing options...
fastbanshee8 Posted June 1, 2010 Report Share Posted June 1, 2010 Sounds like an air leak on the right side, somewhere. Quote Link to comment Share on other sites More sharing options...
Jaystre Posted June 6, 2010 Author Report Share Posted June 6, 2010 ok here is a litle update of where im at after tearing it down i found a broken piston skirt on the intake side of the right cylinder .I retrieve a small piece of the skirt in the base which was stoping it from turning there wasnt any obvious signs of an air leak . a sligtly torn boot but not all the way trough . the right piston has a litlle more slack in the cylinder than the other one 0.005 mm to be exact i believe that is the limit on the left side it was closer to 0.004 . could a lean condition break a piston skirt or was it the slack that could of cause it . hope someone can help me out dont know if i throw new pistons in or go one size bigger in the cylinder im already at 0.020 over thx Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 6, 2010 Report Share Posted June 6, 2010 (edited) You need to mic cylinders to measure out of round and taper. Skirt probably broke from piston slap . IMO, tolerances would have to be less than half before I'd just put new slugs in. The biggest cost will be pistons, gaskets , bout 3-350. Cyl bore maybe 100. You might also have to split cases to remove all debrei , if you do use new crank seals, 20. JMHO, your results may vary. Btw, piston oversizes are in .010 increments, unless you have bad gouges, you should be able to go .030 oversize, still leaves you five more overbore sizes to go. Edited June 6, 2010 by Larry's Shee Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 6, 2010 Report Share Posted June 6, 2010 (edited) http://cgi.ebay.com/ebaymotors/YAMAHA-YFM350-BANSHEE-TOP-END-KIT-CYLINDER-BORING-/320539852991?cmd=ViewItem&pt=Motors_ATV_Parts_Accessories&hash=item4aa1aa00bf . Decent deal right here. Have dealt with Mike on several different bikes. Lakes Motorsports , Waterford ,Mich Edited June 6, 2010 by Larry's Shee Quote Link to comment Share on other sites More sharing options...
Jaystre Posted June 6, 2010 Author Report Share Posted June 6, 2010 http://cgi.ebay.com/ebaymotors/YAMAHA-YFM350-BANSHEE-TOP-END-KIT-CYLINDER-BORING-/320539852991?cmd=ViewItem&pt=Motors_ATV_Parts_Accessories&hash=item4aa1aa00bf . Decent deal right here. Have dealt with Mike on several different bikes. Lakes Motorsports , Waterford ,Mich ok seem like a good deal but i have a 4mil stroker kit so it wouldnt be the same pistons right ...thx for the advice i think im gonna go the safer way and bore it out to 0.030 Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 6, 2010 Report Share Posted June 6, 2010 Lots of good deals ,hit up site sponsers , or whoever. You tell them what you have and they'll set you up. Just be sure you use someone that is familular with 2 strokes. Quote Link to comment Share on other sites More sharing options...
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