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Message: [QUOTE="julien_d, post: 1386559, member: 98751"] factory service manuals almost ALWAYS have compression ratio's in the specs. For instance, 89 kdx200; 7.7:1 high speed, 9.2:1 low speed This is the difference between power valves open/closed. I would not expect a big bore kit to come with such specs, because they do not know what else you may have done or will do to your bike. If you're talking about cranking compression like Tom said, it's only useful as a guide to ring performance. Check it when you put it together, and when it starts to go down from that number, it's time for rings. [/QUOTE]