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Buell Motorcycle Forum » Old School Buell » S2 Thunderbolt » Archive through November 30, 2009 » Thunderstorm head question « Previous Next »

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Senna6094
Posted on Monday, October 05, 2009 - 01:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Hi all,

Can someone tell me what mods, from stock, have been done to the thunderstorm heads?

Thanks,
Dana-C
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Sportyeric
Posted on Monday, October 05, 2009 - 01:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The stock heads on the S2 were 9:1 compression ratio. It had flat-top pistons in a hemispherical head.
The Thunderstorm heads have a piston with a 15 degree dome. The heads have a corresponding 15 degree shelf. This design produces a better burn and allows a higher compression ratio. The valves are also larger.
The Thunderstorm engine became the stock set-up in 98 or 99.
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F_skinner
Posted on Monday, October 05, 2009 - 02:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

allows a higher compression ratio.

10:1 I think.
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Phelan
Posted on Monday, October 05, 2009 - 02:55 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

They were also highlight-less on the fins : D.
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Senna6094
Posted on Wednesday, October 07, 2009 - 12:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Good stuff thanks guys.

One other question.

Im going to have the top end done and while it's apart I'm going to have new rings installed(gaskets are also leaking at the base of the jugs). It has been recommended that I go .010" over and put in new pistons to get the piston/cylinder clearance back to the pre-worn condition.

Where is the bast place to get new 15degree pistons?

Thanks again.
Dana-C
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Phelan
Posted on Wednesday, October 07, 2009 - 02:06 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I'd contact one of the dealer sponsors here. Stock pistons can be had in .010 over configuration, and last I checked they run about $50/ea.
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