We offer two size big bore kits using the OEM cylinder. A 686cc +2mm kit and a 693cc +3mm kit. There is about a 1.5hp difference between the two. We recommend using the 686cc kit so in a few years when you want to freshen it up you can use the 693cc kit without buying a new cylinder. But that is up to you. Also if you have a 686cc kitted Raptor we are the only people who offer a 693cc kit to freshen up your 686cc kit. This is a custom piston CP makes for us we have been using reliably for years. Your stock Rhino 660 has a compression of 9:1. With the extra 2 pounds of compression and bore size you will see about a 6hp gain from bottom to top.
A note on those cheap China made cylinders you see. We get questions on these all the time. Here is why we don't use them. First they are often to large to fit into your engine case and case grinding or boring must be done. Second they come with a cheap low compression cast piston. Third they often have casting flaws in the deck which result in blown head gaskets. And our final thought is it is cheaply made and going inside your engine. That is not the place you want to risk it.
**A stock Rhino 660 bore size is 100mm.
**A Rhino 686cc has a bore size of 102mm.
**A Rhino 693cc has a bore size of 102.5mm (Alba exclusive)
Cylinder core: What makes a good core? Your cylinder does not have to be in good shape to be a good core. We bore 2-3mm which means as long as scoring on the cylinder walls is less than that it will clean up. If your cylinder has been destroyed and a piece is missing like when a rod breaks and goes through is then it is no good. If you are not sure send us a few pics.