sheeban Posted March 18, 2010 Report Posted March 18, 2010 Hey guys so its finally starting to warm up so i took her out for a ride. This winter i bought small bore inframe shears, a pingle, shift star and some bling. Well i did a compression check and had 135 psi in both cylinders so i decided to run 91 this year instead of avgas. So after getting the jetting close i went for a little ride and noticed the plugs came loose so i tighten them up and the same thing happened. Tried new plugs same thing, my timing is plus 4 is this to much for 91. Ive never had this happen before so I'm getting annoyed. Can some one lead me in the right direction. Quote
SAVAGE420 Posted March 18, 2010 Report Posted March 18, 2010 Are you sure 100% that comp gauge is accurate? I would try an other quality comp tester as its deto going on. So what gauge are you using and how old s it? Quote
sheeban Posted March 18, 2010 Author Report Posted March 18, 2010 Are you sure 100% that comp gauge is accurate? I would try an other quality comp tester as its deto going on. So what gauge are you using and how old s it? Well its a brand new Lisle gauge (its what the parts store had it was like 50 bucks) but im not sure just how accurate it is i dont hear any deto but i might not know just what to listen for either Quote
00sheerzr Posted March 18, 2010 Report Posted March 18, 2010 i dont mean to get off topic but what does detonation sound like????? Quote
sheeban Posted March 18, 2010 Author Report Posted March 18, 2010 i dont mean to get off topic but what does detonation sound like????? Well i thought it made a slight knocking sound but im not 100 percent sure Quote
SAVAGE420 Posted March 18, 2010 Report Posted March 18, 2010 i dont mean to get off topic but what does detonation sound like????? D E T O N A T I O N. Knock Knock, Who's There? What plugs are you using by the way? Are you checking it properly? What size domes and altitude are you at? I would check with another gauge just to be sure! Quote
sheeban Posted March 18, 2010 Author Report Posted March 18, 2010 D E T O N A T I O N. Knock Knock, Who's There? What plugs are you using by the way? Are you checking it properly? What size domes and altitude are you at? I would check with another gauge just to be sure! NGK br8es 19cc at 4300 im gonna go buy some race fuel and see what happens you are proabaly right savage Quote
firebanshee Posted March 18, 2010 Report Posted March 18, 2010 You could back your timing off and try it and see if it still happens, or put a higher quality fuel in it and see if it still happens. 93 octane is pump gas were i live do they sell 93 there? that little bit might make a difference. Quote
sleeper06 Posted March 18, 2010 Report Posted March 18, 2010 Its not all about static compression,comp ratio has a big influence on gas needs.Depending on the porting 19cc domes should be in race gas territory.Might be time for a rebuild with those numbers on 19s so make sure your guage is good Quote
bansheesandrider Posted March 18, 2010 Report Posted March 18, 2010 A Lisle gauge should be an OK gauge. Lisle and Thexton supply diagnostic and test equipment to SnapOn, Mac, Matco, so forth to cover things that they don't make themselves. Not saying that the gauge is as good as a SnapOn or a SnapOn is the same thing, but it should be a decent gauge. You definetely have detonation going on, spark plugs backing out is the indicator for that. The quick fix is higher octane fuel. How ever with 19cc domes you should have alot more pressure than that, so realistically, the proper fix is a top end job and the correct fuel. Quote
papa_smurf49319 Posted March 18, 2010 Report Posted March 18, 2010 NGK br8es 19cc at 4300 im gonna go buy some race fuel and see what happens you are proabaly right savage He is a little ways up, i dont know how much that would effect the compression, but it may not be as low as it seems to be because of the altitude. Quote
sheeban Posted March 18, 2010 Author Report Posted March 18, 2010 Well i really dont think that my top end is ready to be rebuit yet im gonna try a diffrent gauge and see what happens. I will report back. Quote
Burt Reynolds Posted March 18, 2010 Report Posted March 18, 2010 YOU NEED HIGHER OCTANE,period. I have never seen a worn top end vibrate a plug out without making horrible noise. Or maybe a crank out of whack really bad,but with those problems the plugs backing out would be secondary to the massive vibration and hammer like knocking you would hear. You said it yourself,you tried different gas,and now the plugs are loosening up,its a no brainer. I would never run +4 timing on 91 octane. Its like removing the packing out of your silencers and then asking why your bike is so loud. Quote
jbooker82 Posted March 18, 2010 Report Posted March 18, 2010 I would bet it is pretty hard to hear on a banshee. Here is a clip. You can bearly hear it. It sounds like marbles rattling around on top of the pistons. http://www.youtube.com/watch?v=Due7mkTHMlw Quote
06specialedition Posted March 18, 2010 Report Posted March 18, 2010 YOU NEED HIGHER OCTANE,period. I have never seen a worn top end vibrate a plug out without making horrible noise. Or maybe a crank out of whack really bad,but with those problems the plugs backing out would be secondary to the massive vibration and hammer like knocking you would hear. You said it yourself,you tried different gas,and now the plugs are loosening up,its a no brainer. I would never run +4 timing on 91 octane. Its like removing the packing out of your silencers and then asking why your bike is so loud. Really? You need higher octane with +4 timing?? Quote
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