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Buell Forum » XBoard » Buell XBoard Archives » Archive through April 20, 2007 » High comp' pistons in a stock XB12 lump question. « Previous Next »

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Fulgur
Posted on Tuesday, April 17, 2007 - 12:57 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Hi All,
I have a question that’s just popped in my mind and is toying with it a bit.
Would anyone know if throwing in a set of 12:1 Wiseco pistons into an otherwise stock XB12 engine would be 1. Possible (would they fit without hitting anything) 2. Reliable (would the various bits of the rest of the bike take it) and 3. Worth the bother (if a piston was broken already)? – In short better than stock.
Would one have to adjust fueling, ignition timing and octane level of the fuel etc?
Note that the rest of the bike would be standard (ECM, muffler, heads, valves etc). I have only ever done this sort of thing on engines that were having other mods so I am not so sure how a stock one would react.
Cheers for any input and if anyone has already done this sharing some of the knowledge would be great.
(I have scanned the knowledge vault but haven't found what i am looking for as of yet)
…..Fulgur.
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Old_man
Posted on Tuesday, April 17, 2007 - 01:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

It seems to me the stock 9 pistons would work with no problems hitting anything.
They would raise the compression ratio, but I don't know how much.
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M1combat
Posted on Tuesday, April 17, 2007 - 04:25 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I believe the stock nine pistons would take you to 14:1. That's a bit too much unless you're racing.

Going to 12:1 is also a bit too much. The highest I'd go without fuel additive or expensive high octane fuel would be about 11-11.5:1
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Trojan
Posted on Wednesday, April 18, 2007 - 03:18 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Fitting the Wiseco 12:1 pistons in the XB12 is absolutely possible.

We put them into our racebike with stock valves, cams, etc and have had no issues at all for a whole year now.

The only thing you may have to think about is detonation. We run 109 octane unleaded race fuel, although on occasions I have mixed this with regular 98 octane unleaded with no dramas.
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Disturbed
Posted on Wednesday, April 18, 2007 - 05:02 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Typically you can count on about 5% more power per 1 point of compression. It is the ratio between the volume of the combustion chamber, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke.
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Froggy
Posted on Wednesday, April 18, 2007 - 02:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Trojan, is that 109 octane RON or R+M?
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Fulgur
Posted on Wednesday, April 18, 2007 - 02:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Cheers all,
98 fuel and maybe a cooler plug then. If it turns out that my piston is bad I might go for this then. I'll be thinking about it. Might do the maths anyway to be sure.
....Fulgur.
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