BansheeRider87 Posted March 16, 2009 Report Posted March 16, 2009 Heres the numbers Piston 1- Front-back top - 2.5068 Front back bottom - 2.5150 Side-side top - 2.5093 Side-side bottom - 2.5120 Piston 2- Front-back top- 2.5066 Front-back bottom - 2.5150 Side-side top - 2.5092 Side-side bottom - 2.5121 Cylinder 1- Front-back top - 2.5210 Front-back bottom - 2.5228 Side-side top - 2.5210 Side-side bottom - 2.5210 Cylinder 2- Front-back top - 2.5208 Front-back bottom - 2.5228 Side-side top - 2.5208 Side-side bottom - 2.5206 Wondering if I need a bore? if i need new pistons? Or can I still run it the way it is and just put it back together The motor never had any problems just doing a complete bike rebuild and want to be sure. Thanks in advance, Todd Quote
blowit Posted March 16, 2009 Report Posted March 16, 2009 (edited) Heres the numbers Piston 1- Front-back top - 2.5068 Front back bottom - 2.5150 Side-side top - 2.5093 Side-side bottom - 2.5120 Piston 2- Front-back top- 2.5066 Front-back bottom - 2.5150 Side-side top - 2.5092 Side-side bottom - 2.5121 Cylinder 1- Front-back top - 2.5210 Front-back bottom - 2.5228 Side-side top - 2.5210 Side-side bottom - 2.5210 Cylinder 2- Front-back top - 2.5208 Front-back bottom - 2.5228 Side-side top - 2.5208 Side-side bottom - 2.5206 Wondering if I need a bore? if i need new pistons? Or can I still run it the way it is and just put it back together The motor never had any problems just doing a complete bike rebuild and want to be sure. Thanks in advance, Todd Yes, bore em. Bores are eccentric at the top by .002. That is unacceptable and needs correctly. First punch is .020 over. Pistons are about .006 clearance right now which is not horrible. If you want to push the envelope, do not waste your money on new pistons for those bores and run the old ones. You have obvious piston slap though and that is causing your excessive wear at the top normal to the wrist pin. Piston cocks in the hole. I will bet the rings are pretty worn. Check the end gap and report back. How are you measuring this stuff? Brandon Edited March 16, 2009 by blowit Quote
BansheeRider87 Posted March 16, 2009 Author Report Posted March 16, 2009 Machine shop in town. There closed now so I cant get the ring measurements. Quote
blowit Posted March 16, 2009 Report Posted March 16, 2009 Bump anyone else? You don't believe me?? :biggrin: Quote
BansheeRider87 Posted March 16, 2009 Author Report Posted March 16, 2009 You don't believe me?? :biggrin: I do.. Just like to see what others can say about it. Quote
BansheeRider87 Posted March 17, 2009 Author Report Posted March 17, 2009 I guess what I am asking is, Can i hone these cylinders and buy new pistons and rings and have it work? Quote
sleeper06 Posted March 17, 2009 Report Posted March 17, 2009 It will run,but it wont last long,and you might have caught major failure before it happened here,you will start to collapse the skirts of pistons and they wont stay straight in the bore Quote
blowit Posted March 17, 2009 Report Posted March 17, 2009 (edited) I guess what I am asking is, Can i hone these cylinders and buy new pistons and rings and have it work? Can you? Absolutely......BUT, per my experience (around 500 Banshee motors now), I would advise against it. I could explain it in as much detail as you care to listen to but the fact is, you WILL be wasting your money but hey, if everyone listened, all us builders would be out of jobs... I know you are waiting on the one reply that will indicate you are "good to go" but the fact is, the bore has a problem. I am going totally off your measurements though and assuming they are accurate. To put this in a nutshell, round ring, oval hole, how does that seal? It does not. Add to this that the eccentricity is at the top of the barrel and will see combustion pressures, the blow by will cause excessive piston heating, carbon fouling of the rings which will lead to more blowby and heat, and then you get to do it the right way, all over again. I guess I rarely explain myself and always come off sounding like an arrogant ass with a keyboard but I guess I have been there, done that. Round rings are made for round holes. Your pistons are not too far out but the bores are the issue. I commend you on getting numbers because it really does take all the guess work out if it. I have no idea how many people come on asking if they need bored because they have 90psi comp. I would say, "ask your builder". With measurements though, we can offer much better advise and mine stands. Bore and do it right or ride it as is for a while longer and roll the dice. Either way, new pistons in those bores is a waste of money. Brandon Edited March 17, 2009 by blowit Quote
deckheight Posted March 17, 2009 Report Posted March 17, 2009 Listen to blowit. I do.. Just like to see what others can say about it. Quote
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