Ok here's what I have so far. I pulled the jug off the bike and measured everything. Out of round, taper, size of piston, compared everything. From what i can tell the cylinder needs to be bored. The largest measurement of the cylinder was 68.12mm and the average was 67.80 so im assuming that is what it was bored to???. and the piston that my buddy put in the jug is a wiseco 66.75mm.It seems like this is the wrong piston for this bore. The out-of-round measurement is out of the service limit which is why im assuming it should be bored. Now here is my question!!!!If i were to have my machine shop bore the cylinder what size should it be bored to??? And what piston size should go along with it??? Wiseco is pretty plain and simple .25mm bigger as you go up, so is that about the same for the bore?? Will the machine shop know what size to bore to if i just buy the next size wiseco??? Somebody with some knowledge hook me up!!!!
Buddy's rebuild gone wrong continued!!
- Thread starter BlasterJ7380
- Start date
well if your biggest measurement was a 68.12 it looks like you need to order a .090 over piston 68.25. unfortunatly that is ur last bore on a stock cylinder
well, to say any machine shop will know what to bore it at is a stretch, my local shop, which has done numerous auto engines for me, overbored my cylinder, it was .008 bigger than the piston, which should have been around .004 max, i would have never caught that, except for when i sent my cylinder to ken oconnor for porting, he immediatly found it, so there went $120 wiseco piston down the drain
thats why ken is the only one to ever touch my chit again.
but you could look at the instructions when you buy the piston, as shee stated earlier, and insist that they bore it to that size
how reputable is the machine shop you plan on using ??? do they normally go bikes and atv motors ????
thats why ken is the only one to ever touch my chit again.
but you could look at the instructions when you buy the piston, as shee stated earlier, and insist that they bore it to that size
how reputable is the machine shop you plan on using ??? do they normally go bikes and atv motors ????
Its a buddies machine shop, they know what they are doing, but they also only work on aircraft parts. I can trust they will bore cylinder to the size that i tell them to, i just need to know what size that will be. Last bore size means time to sell!!!!
Last bore size means time to sell...not worried bout it. Do they make any kind of cylinder sleeve or anything along those lines?
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Absolutely, you could also have the stock bore punched out and a 72mm sleeve installed for a big bore kit.
Top ends aren't that expensive. You can find them pop up on here every now and then. A cylinder which has been bored only a few times usually goes for ~$100 a bore should be ~$50 and a new piston should be about another $100.
Top ends aren't that expensive. You can find them pop up on here every now and then. A cylinder which has been bored only a few times usually goes for ~$100 a bore should be ~$50 and a new piston should be about another $100.
I think i've got it all figured out now guys. Machine shop shoppin tomorrow to get a good price on the bore. My plan is to get a second opinion on all the measurements, just because I'm not perfect all the time...and ill have to get another top end kit and go for it again, with all the right parts and sizes this time lol.
Get the piston before you bore it. That way it will be a perfect fit. Do to production differences a piston may be a "little" big or small , + - .005 , just a number but you get the idea.
I have a top end at Ken O'Connor's right now getting it bored the last bore, 68.25mm
It's the last one but one more good one before something has to be done about a sleeve...
Piston diameters should NEVER vary .005" the specificied cylinder to piston clearance on a wiseco forged piston is .0022" or 2.2 thousandths of an inch. If the machining process left an uncertainty of .005", you'd have siezed up engines and broken intake skirts running all over town.
It's the last one but one more good one before something has to be done about a sleeve...
Piston diameters should NEVER vary .005" the specificied cylinder to piston clearance on a wiseco forged piston is .0022" or 2.2 thousandths of an inch. If the machining process left an uncertainty of .005", you'd have siezed up engines and broken intake skirts running all over town.
