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Piston Numbers???????

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I really dont know anything about the piston numbers (i.e. 13:5:1) what does each one mean? I know thats the HC piston so whats the standard? Also JE has a piston that is 78 mm and one that is 80 mm whats the difference?

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Also what is porting and polishing? I really dont know alot about engines.

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78mm is the stock bore. The 80mm is a big bore.

13.5:1 is the compression ratio. This is generally what High comp pistons are. Race teams and such will use up to 14.5:1 or higher, but they are running on straight race gas. 13.5:1 works well on 91 pump gas.

Sock compression ratio is 12.5:1 for 04-05, 12.9:1 for 06-07, and 13.1:1 for 08. More compression typically gives you noticeably more bottom end power. I put in a HC JE piston in my bike. I notice more bottom to mid. But the bike also revved out better. It pulled real nice.

Porting/polishing. Is where a engine builder will "port" the head, or take away and add material at points in the intake and exhaust ports to get it to flow better. They put the heads on flow benches...

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78mm is the stock bore. The 80mm is a big bore.

13.5:1 is the compression ratio. This is generally what High comp pistons are. Race teams and such will use up to 14.5:1 or higher, but they are running on straight race gas. 13.5:1 works well on 91 pump gas.

Sock compression ratio is 12.5:1 for 04-05, 12.9:1 for 06-07, and 13.1:1 for 08. More compression typically gives you noticeably more bottom end power. I put in a HC JE piston in my bike. I notice more bottom to mid. But the bike also revved out better. It pulled real nice.

Porting/polishing. Is where a engine builder will "port" the head, or take away and add material at points in the intake and exhaust ports to get it to flow better. They put the heads on flow benches...

he want to know what the numbers actually mean:

13.5:1------like what does the 13.5 mean...what does the 1 mean...

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