cgamla Posted May 15, 2004 Report Posted May 15, 2004 I have one cylinder that has a .040 over bore but the other I have to have sleeved now my question is . Do I have to have the new cylinder bored out to .040 over to match the other or can I leave it at stock bore. I would like to leave it there if I could just because it would have more rebuilds left on it. i don't think the difference in displacement would be in an issue I was more concerned about the difference in weight and balance aspects between the two pistons. I am going to use Wiseco pistons. I feel like I'm splitting hairs here so just tell me if there is some major reason not to do this. My machinest seems to think all will be just fine. Has anyone else out there done this? Quote
BenBB Posted May 15, 2004 Report Posted May 15, 2004 Never heard of it being done, and I damn sure wouldn't do it on mine. The thought of that seemingly insignificant weight difference moving that fast at 9000+ RPM just has too much potential for catastrophic failure... Besides, why take the chance when you're gonna reach the limit on the other cylinder eventually anyway. Quote
cgamla Posted May 15, 2004 Author Report Posted May 15, 2004 Unsure of what you meant by reaching the limit on the other cylinder anyway. I wonder what the difference is in weight between two different sized pistons. My machinest said that using different sized pistons was common practice when he built two stroke snow mobile engines. I really did not want to bore a brand new sleeve .040 over . Surely did not want to pay to have the other cylinder sleeved. I'm just bleeding out cash like crazy here. Any other opinions anyone.? Quote
MotulMonsta Posted May 15, 2004 Report Posted May 15, 2004 I wouldn't run 2 diffrent sized pistons...You'll have ballance issues and jetting woes. Quote
picco26 Posted May 15, 2004 Report Posted May 15, 2004 some chicks have a boob bigger than the other and it just ant rite i wouldnt do that if it was mine Quote
BrokeStonedBiker Posted May 15, 2004 Report Posted May 15, 2004 shee with different size jugs are weird looking i wouldnt do that if i were you. Quote
Cotton eyed Joe Posted May 15, 2004 Report Posted May 15, 2004 (edited) I hope I did this right. Forces is equal to the mass times the acceleration. If one piston doesn't weigh what the other weighs at a low rpm you won't notice. Now spin it REAL REAL FAST!! The force will be significantly different in the other cylinder since the reciprocating mass will have more force than the other. That could be hell on a crank and crank bearings. Edited May 15, 2004 by Cotton eyed Joe Quote
BrokeStonedBiker Posted May 15, 2004 Report Posted May 15, 2004 yes, what i would do it ditch the .40 over. i would go with the stock bore and get the other resleaved. some like more power some like stock bore. if you have he extra money i would r sleave the biger bore. Quote
Justintoxicated Posted May 15, 2004 Report Posted May 15, 2004 If you want the most life, definately have them both re-sleeved...Is't it great having a Twin Engine? heh. Might as well get them ported while your at it if you have not, more difference with porting than over bore Quote
FoxBansheeRacing Posted May 15, 2004 Report Posted May 15, 2004 I would definitely not do it either. Another thing to think about is your going to be rebuilding your top end twice as much, because you will have to do both cylinders seperately. You do a top end rebuild on one cylinder, sometime in the near future the other one is going to need it. I say do them both now, so you can keep doing them both at the same time in the future. Quote
nickxc Posted May 15, 2004 Report Posted May 15, 2004 I agree that the smartest move would be to re sleve both jugs and have them both at stock bore. But if you dont want to spend that kind of money resleve the one you have to and bore it to match the other. .040 still leaves lots of room for more bores if you need them. But I would definately not put it together with two different size pistons. Quote
frocashmoney24 Posted May 15, 2004 Report Posted May 15, 2004 i asked this question awhile back, people only do it in a pinch, for a quick run, its nto wroth it, the crank keeps itself in balance with the weight of the 2 pistons, i'd keep emt he same if i was you Quote
cgamla Posted May 15, 2004 Author Report Posted May 15, 2004 thanks for the input guys. I'll just eat the bill and get em both resleeved. Found a deal on some Wiseco 64.25 mm pistons on the bay today anyways. After these things are bored and honed to match the pistons will the ports have to be chamfered so as not to catch a ring or anything? Seems to me the last time I had one done the edges were so sharp. If so whats the best method? I just dropped in a new Wiseco welded hot rods crank from TDR yesterday and I swear if this thing blows up again I'll burn it to the ground in my front yard while signing a loan on my new yfz. Between the crank and the parts and labor for the top end I got 900+ bucks sunk into the damn thing. This is the third crank this year and the 4th set of pistons. Oh my aching wallet!!!!!! Oh and on the boobs thing if you get real real close you can't tell if they're diffferent sizes and they look really big too. Quote
MotulMonsta Posted May 15, 2004 Report Posted May 15, 2004 Why re-sleeve? Just bore them to match. Quote
cgamla Posted May 16, 2004 Author Report Posted May 16, 2004 because the one that need resleeved in the beginning was damaged beyond repair due to debris from a broken skirt . The other beleive it or not was originally bored with a slight offset which made the sleeve extremely thin on one side. It wasn't much maybe 60-80 thousandths but definately enough to effect cooling on larger bores. How much can you take a stock cylinder out to anyways. Every thing has it's limits. Quote
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