bansheeigo Posted February 19, 2004 Report Share Posted February 19, 2004 Hi guys,first time on this forum,i opened up the head of my banshee and found that the left side piston had a hole on top of it and then looked at the right side and it almost started to have a hole on that side too,my question is why did it have a hole on top of the piston,i was thinking that my water pump went out and got too hot. It needed new pistons anyways.3 1/2 years with these pistons.What do you guys think what made this happen? 97 banshee coolhead 21cc domes wiseco pistons (.020) 207 above sea level Quote Link to comment Share on other sites More sharing options...
SDD Posted February 19, 2004 Report Share Posted February 19, 2004 Your 21cc domes on regular pump gas made the piston vents. Quote Link to comment Share on other sites More sharing options...
99Red_Roostr Posted February 19, 2004 Report Share Posted February 19, 2004 Running to lean is it. Quote Link to comment Share on other sites More sharing options...
Ducman Posted February 19, 2004 Report Share Posted February 19, 2004 A hole in the piston is from detonation. With 21cc domes and a stock bore W/no porting, W/no timing advance or up to about +3 advance or so you should be able to run 91 octane pump gas without detonation issues. If you ran it with lower than 91 octane fuel or the fuel sat in the tank for too long and went bad this may have caused your detonation problem. You may have ran it too lean on the mains which could also lead to detonation, or a combination of lean and low octane/bad fuel. Make sure the case is clean of any piston fragments/debris before throwing another set in. Quote Link to comment Share on other sites More sharing options...
BansheeBrian Posted February 20, 2004 Report Share Posted February 20, 2004 Definetly check the water pump impeller.Those plastic things love to melt away. Quote Link to comment Share on other sites More sharing options...
cdw Posted February 25, 2004 Report Share Posted February 25, 2004 Too much air, not enough gas------------------------>JETTING Buddy's right about the bad old or dirty gas. It only takes a speck of dirt in your jets to pop a piston. Have someone take a looksy at your carbs. Someone who knows their shit. Quote Link to comment Share on other sites More sharing options...
96shee84z28 Posted February 28, 2004 Report Share Posted February 28, 2004 you need to run higher octane gas... i did the same thing but i was running 20cc domes with pump gas and it put a hole right through the pistons. i started running av gas it about 110 octane and it runs great now. Quote Link to comment Share on other sites More sharing options...
wesw Posted February 29, 2004 Report Share Posted February 29, 2004 i got 20 and am run 91 octane and havent had a problem. its jetting. you probably have something different than stock. and ran it wide open for a long time and smoked a hole in it. Quote Link to comment Share on other sites More sharing options...
bansheeigo Posted February 29, 2004 Author Report Share Posted February 29, 2004 I've had these wiseco pistons(.020) for three years,it was bad gas(91 octain)and it was time to change them anyways.Now that i know to check the compression so this won't happen again.I've learned alot from you guys,THANKS FOR ALL YOUR HELP. Quote Link to comment Share on other sites More sharing options...
bansheeigo Posted February 29, 2004 Author Report Share Posted February 29, 2004 CORRECTION:::::my pistons are 21cc when they blew not 20cc. Quote Link to comment Share on other sites More sharing options...
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