Bore Size HELP

jman2-stroke · Jun 26, 2014

So I wanted to re-ring my R to freshin it up a bit. I havent had the quad that long but dont think guy before me took great care of it.
I have a question about what size rings i will need. 66mm is supose to be stock and the guy I got it from said it was stock. But when I took a digital caliper to mesure the bore im gettin like 68.3mm. So now idk if it has been bored over a little or if its normal. I would think that the part of the cylinder would be even bigger than 68mm because I couldnt get the jaws of the caliper very deep.

Any one know what I should do.

acecarlos · Jun 26, 2014

66 MM is the stock bore...as it left the Honda factory.

68.30 MM is likely a 68.25 MM piston Kit....therefore; you would need a set of 68.25 MM rings.

You really need to have your bore checked with Bore gages to determine the actual bore size, and what piston to cylinder clearance you have. It will also tell you if the current bore is round, straight and if it can be used as is or does it need to be Honed, or go to the next bore size, in this case 68.50 MM.

Any decent local machine shop can measure your bore with accuracy...FYI

Carlos

american opel · Jun 27, 2014

I think he meant 66.3mm.that's to big for a stock 66mm piston.

TimSr · Jun 27, 2014

Wire brush the top of the piston until you can see the numbers on it. If the only marking is an arrow, it is probably an OEM stock. Otherwise it will have an overbore size, or a part number on it. make sure you know what kind of piston it is. Wisco and OEM rings are not interchangeable.

acecarlos · Jun 29, 2014

x2...or it can be a ProX piston kit as well if the 'ink' mark has disappeared like they do on OEM piston kits.

Carlos

jman2-stroke · Jun 30, 2014

Thanks for the help guys. Im gonna get the jug off tonight and finally find out. I plan on doing my own work but does anyone know any engine builders in the U.P. There is a few dealers around but there man hour prices are sky high and shit for serves.

Bore Size HELP

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