12.0:1 High comp pistons for thunderstorm heads

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Wracul

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Apr 6, 2012
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Hi

Im new at this forum so please be gentle. :)


I have a 99 X1 with thunderstorms. And im interested in getting some high comp pistons (11.5:1 12.5:1) because of the octane levels of the fuel in my country. (gas station only selling 95 and 98 octane lead free)

This winter im splitting the engine to repair the infamous engine mount tab on the thunderstorms. So it would be nice with a high comp swap.

My question to you guys is where in the world do i get them? I have searched the internet for several hours without any luck.


Karl
 
I'll call them. can only find 10.5:1 wiseco pistons on their site.

Any other ideas without a lot of headwork/machining?
 
I think 9 pistons in 12 jugs gives you 11.5/1 compression, but I'm not positive about that
 
Ok, the xb cylinders are also interesting because of the larger ribs. Im not familiar with the xb's. What about the motormounts on the heads? The thunderstormheads have these mounts. Do the XB heads also have them?
 
I don't know anything about the tubers, but the thunderstorm heads are the XB heads, so,,,
 
The thunderstorm heads have a 30 deg. machined squish chamber and the XB heads use a flat squish area so the piston has to be matched to the head your using. www.woessner-usa.com has the correct pistons your looking for.
 
I was aware of this twobuells. Thats why i asked if the xb heads had mounting tabs for the frame? No use trying to put xb9 pistons on a engine with thunderstorm heads.

I'll contact woessner about the pistons
 
So, the heads on my '08 "Thunder Storm" motor are not Thunder Storm Heads? I'm haven't dug that deep into these engines, I just figured that was why it's called that
 
Hi

Im new at this forum so please be gentle.


I have a 99 X1 with thunderstorms. And im interested in getting some high comp pistons (11.5:1 12.5:1) because of the octane levels of the fuel in my country. (gas station only selling 95 and 98 octane lead free)

This winter im splitting the engine to repair the infamous engine mount tab on the thunderstorms. So it would be nice with a high comp swap.

My question to you guys is where in the world do i get them? I have searched the internet for several hours without any luck.
Click to expand...

Careful.
a lot of countries rate their fuel using different standards. Your 98 octane may very well be equivelent to our 92.
The air cooled Buells (XB's/ Tubers) are not very tolerant of super high compression ratios on typical (not race) gas.
 
Thanks for the info captain chaos. In Norway we use the definiton of Octane in RON (Research Octane Number) In the US you use the definition of octane in AKI (Anti Knock Index)

98 Octane(RON) equals 94 Octane (AKI)

95 Octane(RON) equals 91 Octane (AKI)

These are the only types of fuel at ANY pump here in norway. And all gas station have them. The difference in the price of these two types are minimal.

I wouldnt call this race gas. But I believe with our gas, its less chance for trouble when running an engine with higher comp.
 
I run 93 in my bike(USA....I thought it was the RON method but maybe I'm wrong and it's the AKI method....)

When I sit in traffic sometimes(can't avoid it sometimes) the bike gets REALLY hot and when I first get moving again it'll sometimes start to knock/ping. I wouldn't do higher compression in my bike, for my application. If you do any long sitting at all and get the bike real hot maybe rethink this...
 
Well im not very nervous doing a high comp piston swap. I live in the cold fjords in norway. No traffic, and a lot of fun roads in the mountains. Im not in doubt it would be a good swap.

I have mailed several companys trying to get some help. The only 12.0:1 pistons i found was with the NHRS 1474CCM big bore. Its almost impossible getting a good company here in norway to do a case boring without me needing to sell my house and my car. And doing the bigbore kit brings out the need of work on the heads. So the 1474ccm is not going to happen in near future.

Im still willing to get a bolt on 1250ccm kit with 12.0:1 pistons if its possible getting one.
 

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