Boring a 2 stroke.

[Jim mac]

I posted earlier Im going to take my cylinder to have it checked out at a machine shop. its a 84 250R Piston came apart, and left aluminum on the cylinder.
Okay, what do I ask the machinist to make sure we're on the same page when we are talking machine work? Ive done chevy V8s but never a 2 stroke. I read about chamfering the ports, so the rings don't catch. Is there anything I may be missing. I found the guys number in the phone book for motorcycle machinework. Im just looking to do a stock top end.
Again thanks all for any and all info. Jim

[Erics350x]

you'll need to look on top of your piston to see if its standard or over bore. then check with the machine shop and see what size piston kit to get before you have it machined .

[InPiEcEs]

Just make sure he follows the piston maker's clearance specs,if it is not an OEM piston, and don't go too tight, it's air-cooled. If it has an exhaust bridge, maybe relieve it a little , or at the very least drill the oiling holes in the piston. The aluminum in the jug will come out with a hone or a bore. Just make sure you have him check the cylinder to make sure you actually need a bore. You may just need a hone, and a fresh piston/rings.

[Jim mac]

piston says 1.25mm on it. where do you drill oil holes? Jim

[MTS]

piston says 1.25mm on it. where do you drill oil holes? Jim

No need to on a air-coold R they have no exaust bridge, You using a wiseco orf a stock Honda piston? cause if you use wiseco Make sure the machinest Bores it out to run .0035-.004 piston/cyl Clearnce, Wiseco only calls for .003 but its not enough they expand alot more.

[Jim mac]

I just dropped it off tonight, he's hoping it'll clean up at 1.5 but may have to go to 2mm. And its a wiseco piston.
He's charging me $40 for the bore
15 for the top end gaskets
12 for the connecting rod bearing
140 for the piston kit with pin.
I priced it around and can save a few bucks on the net but I can pick this up at his shop next week and everything will be good to go.
Does the extra .0005 make that much difference? thanks Jim

[don250r]

the Wiseco pistons have more silicone in them than the Honda pistons.
experienced 2-stroke machinists know that the wiseco's expand more than the honda's because of this.