I have a 04 rhino 660 that needs to be rebuilt.Should I bore out the cyl and go with a oversize piston and rings or buy the 686 big bore kit that comes with everything? I am using the rhino for trail riding no racing or work.
Bore it out to 102mm which will make a 686 as Craig mentioned. Benchmark, Wellers, Pro Shop, KMS and Racers Edge can help you out. DO NOT have a piston milled to lower compression. It will sit to low in the cylinder. I talked to CP and they recomend, at 11 to 1 to mix race gas with 91. I had them make a 10.5 to 1 piston for me that will safely run on 91 pump gas. With no detonation issues. Alot of guys are running 11 to 1 ratio with no problems, I just wanted to be safe and not have any issues with some of the crap gas out there!. Greg at Unleashed UTV helped me with getting the piston as he is a dealer. He had CP make a couple of extras and has them for sale. Give him a call, he also has the Cometic top end gasket kits for the different bores.
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