BannedCR500Riders.com

my jug is at the machine shop right now getting honed. as i guessed, it didn't need boring at all, just a little honing and i'm gonna throw a new set of rings in there. it ran fine in the 94 chassis. i just wanted to get them to check it while i had everything out before i start the AF swap. the question is, how do i tell what brand piston it is so i can get the right rings? wiseco says their rings only fit wiseco pistons. i need to call and see what size rings to order too. before i call, does he measure the piston, or the cylinder to find the piston/ring size? i'm sure he knows since he's been building dirt track/ATV/dirtbike engines and been a machinist for 30+ years. i just like to make sure before asking, since i know for sure from the previous owner that it has been bored before a while back. i ordered a wiseco wristpin, wristpin bearings, and a set of wiseco and proX circlips already.

on a side note, what is this i keep seeing about drilling holes in the piston skirt? what is the reason for this, and do i need to do it?

You should never have a cylinder bored without measuring the piston that your going to use. Just because it says 90mm on the box, doesn't mean its exactly 90mm.

Wiseco's need to have the holes drilled along the skirt to prevent cracking and seizure along the exhaust bridge.

Heres some more info:

http://bannedcr500riders.com/board/viewtopic.php?t=200

Post a picture of it and someone will know what brand it is. To order rings, you just need the nominal size of the piston.

Cam_Ron wrote:You should never have a cylinder bored without measuring the piston that your going to use. Just because it says 90mm on the box, doesn't mean its exactly 90mm.

it's not being bored. it's being honed. the piston that was in it when i tore it down is the same one going back in. there was nothing wrong with the rings that were on the piston when i took the jug off, and it ran perfectly fine. i just wanted to replace the rings when i put it back together. the only reason i took it apart was because it's going in a bike that will be driven on the street 95+% of the time, and i'd rather check everthing before i put the engine in the bike. i've read that thread, but it doesn't mention the piston holes

i'll take a picture of the piston when i get the jug/piston back from the machinist. i'm guessing that will be this week or next.

if your piston is forged, drill the holes and relieve the bridge. if its cast don't drill anything, just clean up the bridge and run it.

just ordered a Honda OEM standard bore piston. do i need to relieve anything on it or drill any holes? after honing the cylinder, does anything else need to be done to it?

the OEM piston is cast. don't drill it. make sure the exhaust bridge is relieved check, your ring gap and RIDE.

good move buying OEM.

thanks. good to know. it should be here tuesday, and i need to go pick my jug up. then i'll assemble it and might get started on the swap in the next week or two.

south central hoon wrote:the OEM piston is cast. don't drill it. make sure the exhaust bridge is relieved check, your ring gap and RIDE.

yup. if your running stock piston, do it like it was from the factory. no holes, slightly relieve the bridge, check ring gap and ride

100hp honda wrote:

south central hoon wrote:the OEM piston is cast. don't drill it. make sure the exhaust bridge is relieved check, your ring gap and RIDE.

yup. if your running stock piston, do it like it was from the factory. no holes, slightly relieve the bridge, check ring gap and ride

by relieving the bridge, you mean take a slight amount of metal off the edge of the piece running in the middle of the exhaust port, right?

LAYNFRM wrote:by relieving the bridge, you mean take a slight amount of metal off the edge of the piece running in the middle of the exhaust port, right?

not just the edges, the whole bridge