Bigger piston, more compression?

[sidecase]

I had my cylinder at a local machine shop. He screwed up the bore. His set my cylinder up wrong in his boring machine and now my bore is a little off center. He calls me at work and say the .020 wiseco piston is too small, I better call and order a .040 over piston. 15 minutes later, He calls again and say " did you order that .040 piston yet?". I told him no and he said " good, your going to need a .050 over piston" . I'm thinking what the hell is going on here? So I rushed over there and told Him that obviously he doesn't now what the hell he is doing. He says my machine is only a year old and tried to tell me that it was crooked from the factory. I told him he was full of **** and I thought he was trying to cover up the fact that he bored it of center by mistake. The bike was on the stock bore. Long story short, I got my cylinder and my money back and have since found a repitable shop. The shop told me that they can correct the other guys mistake but the final bore will be .060 over stock. The last bore for this cylinder is .080. My question is does wiseco compensate the thickness of the dome of the piston to offset the a compression increase from the larger bore diameter? Or will I have to modify the head to keep the compression stock? The compression reliefs that were ground in from the factory above the exhaust ports are now ground completely out by going .060 over the stock bore. Should I expect any changes in power delivery. Any help or comments would be greatly appreciated. Thanks, Larry

 

[Jake T]

Sorry this doesn't answer your question but why the heck
would you bore out a CR500? Cripes, I'm scared of my dad's 250....

 

[atc3434`]

Man, what the hell was that guy doing? Geez, I'd have made him pay up for a new jug. I wish I could help you with your actual question... maybe a thicker head gasket would relieve a little compression if your afraid it'll be too much. Sorry I could help more... but hey, at least its a bump back to the top. ;)

 

[Rcannon]

If your cylinder was being boored, was it due to damage? If so, the machinist may have had to overbore more to fix it? 

 

Is this possibl eor was the guy drinking too much? I am very curious. Erics book did make mention of head mods being needed if the bore became larger. I imagine you could ride it for a short time and see if the larger bore caused any problems.

 

[Faded]

Reassemble after getting your cyl back. Gently tighten the head down. Put a piece of solder (bent into an 'L' shape) in through the spark plug hole, like if you were going to measure squish. Let the end contact the side of the bore. Hold it there while cycling the motor with the kick starter. After the piston has past TDC pull out your solder and see how thick the end is (measure it with calipers). If there isn't enough relief (i.e. piston hits head) and you run it you risk damaging your motor. Or give Eric a quick call ( www.eric-gorr.com ) and ask him, he'd know. If it needs the head mod he does a sweet job for not a lot of $$$.

 

[sidecase]

Thanks for the info guys. I guess the the cylinder is a total loss because the first machinist bored it off center. I got the phone call fron the second machinist at a reputable bike shop and he said that the bore was so far off center that he would have to go to an .080 piston to get it straight. I think that I am going to explore my options of small claims court. I really don't know what my chances are because I never received a receipt from the first machinist. I did get my money back though. So I guess it would boil down to his word versus mine. I have all ready ordered a new cylinder from service honda. Wow, what a costly lesson I have just learned. I guess I can always hurt this lowsey machinist by word of mouth. What hurts really is that a local suzuki dealer sends all their work to him and thats who they recomended.

 

[Glitch]

Why dont you just go to an .080 over piston, thats alot cheaper than buying a new cylinder?

 

[Studboy]

Or you could resleeve the one you already have.