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XB9 pistons in XB12 engine
https://ukbeg.com/forum/viewtopic.php?f=8&t=1207		 Page 1 of 1
Author:  gunter [ 23 Jun 2009 08:47 ]
Post subject:  XB9 pistons in XB12 engine
Anyone here, who put XB9 pistons into a XB12 engine to achive a higher compression? I searched the archives but didn't find anything regarding this in there.
Author:  pash [ 23 Jun 2009 09:05 ]
Post subject:  Re: XB9 pistons in XB12 engine
Is this any help?

xlforum.net/vbportal/forums/showthread.php?t=156101
Author:  gunter [ 23 Jun 2009 15:13 ]
Post subject:  Re: XB9 pistons in XB12 engine
Yes, thanks a lot. This gave me the impression, that it's possible to use the XB9 pistons. In the thread thinner gaskets are mentioned, are thicker gaskets available also?
Author:  pash [ 23 Jun 2009 16:46 ]
Post subject:  Re: XB9 pistons in XB12 engine
Yes, from www.nrhsperformance.com/ I believe.
Author:  Blackrag123 [ 24 Jun 2009 08:23 ]
Post subject:  Re: XB9 pistons in XB12 engine
Gunter off the shelf gaskets available in 30 or 40 thou from cometic also use sealer and no base gasket..............high comp tho???
Author:  gunter [ 24 Jun 2009 09:46 ]
Post subject:  Re: XB9 pistons in XB12 engine
I took a look at wiseco.com, and they are selling similar pistons for XB9 (stock compression) and for XB12 (high compression). Although different part-# (4833Px vs. 4832Px) dome volumes and clearances are indentical. Will have to talk to LuckyHands about this anyway (and I know what he's going to tell me :headbang:).

From scanning the Badweb, most people are afraid of pinging, but this seems due to lack of higher octane fuel, which is not a real problem in Germany. 95 RON (Euro-Super) is available everywhere, 98 RON (Super+) widely spread and Shell/Aral/BP 100 RON (V-Power/Ultimate) also.

I am not concerned about engine life. 100% of my Buells had/have engine failures while running bone stock. So if they fail anyway, why not have some fun before? Next failure will make the bike directly go to a breaker.
Author:  milkster [ 24 Jun 2009 21:58 ]
Post subject:  Re: XB9 pistons in XB12 engine
Hi Gunther, i recently rebuilt my xb after the gearbox lost 2nd gear,anyway i`ve changed the motor from 984cc to 1203cc and was advised to use xb12 pistons with the new crank rather than the domed xb9 pistons as these would give a compression ratio of 12:1, I would be reluctant to do this conversion with the standard needle roller crank bearings,HTH
Author:  gunter [ 25 Jun 2009 07:25 ]
Post subject:  Re: XB9 pistons in XB12 engine
Yes, this is a valid argument. Crankshaft bearing are THE weak point, that is still keeping me away from switching to domed pistons. On the other hands, I do not know about a single big bore (14xx cc) engine in Germany that failed - if the crankshaft had been aligned properly before. I think these engines have higher torque than a high compression 1203 cc engines, so the crankshaft bearings will be stressed even more.
Author:  gunter [ 25 Jun 2009 22:34 ]
Post subject:  Re: XB9 pistons in XB12 engine
We split the case today and found absolutely nothing that would explain the knocking noise from the engine. It's completely undetermined what might have caused it. Nevertheless, the crankshaft pin showed some pitting and will be replaced, a good reason to align and balance the crankshaft again. As a preventive maintenance all transmission bearings are replaced. Le maestro forbade me to use domed pistons to rise compression, so no XB9 pistons will be installed.
Author:  pash [ 26 Jun 2009 05:48 ]
Post subject:  Re: XB9 pistons in XB12 engine
How many kms has this 12 done?
Author:  gunter [ 26 Jun 2009 07:47 ]
Post subject:  Re: XB9 pistons in XB12 engine
28 tkm.Noticeable loads of oil carbon on top of both pistons. Regarding the oil pressure problem (which started everything), nothing remarkably was found too.
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