piston sizing

98blaster+4

Member
Oct 12, 2008
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vermont
so if you read my other post "help needed bad" you know im having troubles
what i now need to know is what does +4 mean refering to piston
it is a wiseco
any recommendations on whether to leave it the size it is or go bigger are greatly appreciated
 
not sure about a +4 piston never heard of it before. usually on here +4 is refering to a stroker crank or a swingarm. as far as boring it to a bigger size it should only be done when absolutly necessairy because it doesn't add any real power at least none that you would ever feel. and each cylinder can only be bored over so many times so no reason to waste them if you dont have to.
 
not sure about a +4 piston never heard of it before. usually on here +4 is refering to a stroker crank or a swingarm. as far as boring it to a bigger size it should only be done when absolutly necessairy because it doesn't add any real power at least none that you would ever feel. and each cylinder can only be bored over so many times so no reason to waste them if you dont have to.

Agreed. Your only gaining a few cc's with every over-bore.
I guessing +4 means the 4th over-bore or 1mm over.
 
i disagree. i think you should go to the next over bore w/ every new top end rebuild for a couple reasons.
1.) you've got like 7 or 8 overbores in any stock sleeve anyway. you only need to go 0.010" every time.
2.) a hone on top of the already broken in cylinder will put too much clearance between the sleeve and the piston and the piston will flap around. this happened to me cuz i was lazy w/ my last set of rings and the piston got completely chewed up on the exhaust side by the exhaust port. that meant a bottom end rebuild and a new piston anyway!
3.) you'll lose compression if you just try to put a new set of rings in w/o a hone. and a deglazing bit is usually not good enough.
4.) it's a good opportunity to replace the worn top end bearing and wrist pin. and top end gaskets.
5.) it's a good opportunity to de-coke the head.
 
If you have the money a CT Racing 240 kit is the way to go a little over 1500 bucks but it comes with everything new jug, new carb, new pipe. if not the vitos 12-port is ok, about 500 bucks. But it deffinantly needs porting the stock porting sucks. if you want to go a little cheaper then just send your jug to Flotek he can get more power out of your stock jug by just porting it than you will get out of the stock vitos 240 kit. I got the vitos kit and had Flotek port it and am very happy with it. but keep in mind that any of these options is probably going to mean a new carb, pipe, and reeds.

As far as boring goes the only way to tell is to measure the cylinder and call the piston maker to find out the excact size of the piston. I believe most cylinders require .0015" to .003" of piston to cylinderwall clearance and at .005" it usually time to bore but remember after a hone and break-in cycle the cylinder will gain about .001" so if its .004" before you hone it, it will be .005" after its broke-in and thus loose enough that it may cause the skirt to catch a port.
 
its already got boyseen reeds on it along with a powercore 2 silencer
i was planning on a new pipe anyways
winter is when the tourists come up here to killington so i will be makin some good loot im gonna go through this whole bike,especially now that its broken

what is the best way to go as far as boring it out should i stay with only one size up or should i wait and go big?

i like speed
what would be a good reliable setup for somewheres under 2 G's?
whole quad not just the engine