sheerider11 Posted February 16, 2014 Report Share Posted February 16, 2014 A very respected builder once told me that wrist pin grooves do not effect performance, since they are below the exhaust port opening height and therefore do not effect compression. I have no experience with that. Just what I was told.God damn it, it does make sense. Quote Link to comment Share on other sites More sharing options...
joey83 Posted February 16, 2014 Report Share Posted February 16, 2014 The wrist pin groove will be on an area of the cylinder that the skirt rides on. So it could rough up the skirt. The skirt hits 90% of the upper cylinder and the rings are now sliding on a grooved cylinder. ? Quote Link to comment Share on other sites More sharing options...
joey83 Posted February 16, 2014 Report Share Posted February 16, 2014 I have a 64.5 or 65 cylinder. Just cant remember which side it is. PM if you dont find what youre looking for and I will go dig around. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted February 18, 2014 Report Share Posted February 18, 2014 I came upon the same situation 4 yrs ago on a friends machine factory piston lost clip and wrist pin chewed cylinder. I ported it bored and ran it, he is very cheap and understood the reprocutions . Needless to say he has been spraying the death outta this motor for three yrs and still have acceptable compression it dropped 3 psi . Wrist pin ate the sleeve and bottom of one transf inlet Quote Link to comment Share on other sites More sharing options...
Young Guns Racing Posted February 20, 2014 Report Share Posted February 20, 2014 I could see where it might not effect compression as much but to have the rings and skirt travel on an uneven / grooved surface is asking for trouble. I would never recommend doing such a thing, but everyone is different and if it makes that individual happy - then ride on lol. Its one of those situations that could work for 5 minutes or 5 years. Is what it is. Your going the right route sleeving both. Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted February 20, 2014 Report Share Posted February 20, 2014 ive been riding on a cylinder that had the cir-clip pop out and make two grooves on the cylinder wall, pretty deep. I bored to the next size(not because of that but because they needed to be). the two grooves look awful but they are below the exhaust port and doesn't affect compression or ring life. take a picture of the damage OP, maybe its way worse then what you describe, maybe its not that bad at all? Quote Link to comment Share on other sites More sharing options...
Starwriter Posted February 20, 2014 Report Share Posted February 20, 2014 People think that the rings traveling over the wrist pin grooves is harder on them than traveling across the ports? Really? Not even. Quote Link to comment Share on other sites More sharing options...
camatv Posted February 20, 2014 Report Share Posted February 20, 2014 yup and a multiple bore size engine is going to twist a crank out of phase........ the transfers might be bleeding some off and doing a lil bit of weird stuff on the intake charge. but hey if your cheap and just want to ride..... again. if your going to go through all the trouble of getting new cylinders or sleeving both used ones then match boring and new pistons probably be the same price as a cleaned up serval or cub.... if your ok with running 66mm then run it. its out there on a stock cylinder and your chances of skirts breaking are pretty high. or not.. depends on the ride time.. i have had people tell me their motors built by bla bla have lasted over 6 years. but they ride the bike 2 times a year at festivals. and basically just put out the the big dunes and down to the bathrooms.. it can get really easy to way overthink these kinds of situaions... rember K. I. S. S. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted February 20, 2014 Report Share Posted February 20, 2014 If your considering sleeving one cylinder then I'd do both with big bore sleeves. Why not gain some cc's while your at it? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted February 20, 2014 Report Share Posted February 20, 2014 If your considering sleeving one cylinder then I'd do both with big bore sleeves. Why not gain some cc's while your at it?Ok, if we've made it this far. I have to agree with booker even though I'm not a big fan of the big bore sleeves these days. They bring on complications of sealing issues as well as the cost involved to correct them. But if you are already set on sleeving them, might as well make it bigger. The trick is to have the transfers worked over while the sleeves are out. Only problem I see at that point is that every detail to set up a proper big bore stock cylinder will probably cost as much as an aftermarket jug set up. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted February 21, 2014 Report Share Posted February 21, 2014 It also depends on what sleeves you go with. I had a set of patriot racing cylinders resleeved with 66-68mm bore sleeves. They were not the huge ones where the lip of the sleeve goes clear in to the head bolts. They also didn't make the transfer ports any narrower because there was still aluminum against the new sleeves. Some of the larger big bore sleeves make the transfers narrower because they go in to them. I just ran blaster pistons, and big bore blaster piston domes on a 4mill long rod crank. I didn't have any sealing issues. I ended up selling them because the power delivery of a stock cylinder drag ported 4mill didn't go good with where I ride. I had Patriot Racing do the resleeve because they know their porting and would be best to match up the new sleeves to the cylinders. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.