They're not very common. Farrow's had one this summer, and before I could even get to look at it, it had sold.
If I was going to build a XLCR clone, I'd use an S as the base.

 

1200s did not have Thunderstorm heads. They are plain old 1200 heads with an extra spark plug.

 

I bought my wife a 98 1200S and sold it three weeks later for 500.00 more than I paid for it. Nice bike, but my 04 1200C (that she inheirited) was better in every aspect.

Shakey

 

I don't think so they have a 12 or 15 degree squish band and bump up your compression to 10:1 I believe, a little bit more than a stock 1200 head with an extra plug.

 

Ive got a 98 1200S that I bought this past Spring... and it only had 1,411 miles on it total. Sure does run good. Ive also wondered... how many were made and how rare is it. It also has 6 more stock HP than the std Sportys.

bob

 

Sorry dude but you are wrong. I just looked up the pistons for a 1200s and the 1200 custom and sport use the same pistons. They do have more compression but it has to be slightly smaller combustion chamber because they also us the same head gasket, could have something to do with the cams also because Harley doesn't specify if they are talking static compression or cranking compression .
The Sport was only rated at 78HP off the show room floor and that was at the crank not at the wheel which is 22hp behind any Thunderstorm.

 

96 through 03 XL1200S used the "lightning" heads with a 10 degree squish band cast into them. By your own admission if they both use the same piston and head gasket yet have different compression ratios they must be more then the same head with an extra hole for a spark plug.

 

This article describes the heads as "high compression dual spark plug heads" and under the engine specs the piston size, bore & stroke & displacement are the same as other models. That would lead me to believe that there is something different about the heads other than the extra plug causing the jump from 9.7-1 to 10.0-1 compression ratio.
http://www.totalmotorcycle.com/photo...r1200Sport.htm

 

Well here is the staight scope on Lightning/1200s heads (I did some research on the subject) guess what we are both kinda right.
The old original s1 lightning and the 1200s share the same heads and the reason for the increase in compression is the chamber is 5 cc's smaller they do have a 10 degree squash band but it doesn't do anything because Buell/Harley never used the matching pistons in prduction bikes and they have the same exact valves and air flow as a stock 1200 head.
They definitly aren't Thunderstorm heads.

 

I thought the Ligntning was a Buell model bike and Thunderstorm is a performance head /piston mod from Buell. Maybe this article can shed some light, particularly for 2003S model. http://www.sportster.org/tech/evo-tech/heads.shtml