| Author | Message | ||
     Cjburr |
Someone asked me about putting together this combo on an 883 Sportster, XB9 jugs/pistons and Thunderstorm heads, I told him the best place to ask that question would be here so here I am asking. All comments welcome, thanks, Chris | ||
| Cjburr |
thinking about this some and seem to recall the "9" being a destroked "12" am I off the track ?? if it is then would this be no different than a 1200 Thunderstorm conversion ?? are the pistons in the "9" the same as the "12" and the destroking allowing more RPMs ?? I may be wrapping myself around the axle here  | ||
| Cjburr |
one more thing the bike is an 05 883 so it has the piston squirters which may influence whether you can use those pistons or not. | ||
| Bad_karma |
Chris From what I have read here the XB piston aren't compatible with the thunderstorm heads. Hopefully someone with experience will confirm or deny. The nine is in fact a shorter stroke. I know some of the XB12 people use the 9's piston to get higher compression. Not sure if the piston/head combination you are talking about can be machined to work. Try the over sized XB piston/sleeves in a 1250 kit (no case machining required) and newer sportster heads that are basically XB heads (these still have the mounting for the carburetor to the side). Will make a sweet sleeper. Hope I was of some help, good luck and am interested how this turns out. Joe | ||
| Rick_a |
He needs XB9/12 pistons and the 04+ XL1200 heads. They are the same as the XB heads only they have the aircleaner mounts drilled. The stock 883 heads use a combustion chamber/port design that's unchanged since 1987. XB12 pistons give 10.2:1 CR, the 9 give around 12.5:1 which is pretty radical for a street motor (depending on altitude and cam profile). Another alternative is flat top pistons and the Screamin' Eagle heads for '04+. They come setup with springs to handle up to .575" lift and are decked for 10.5:1 CR with flat tops. CJburr, That is correct, the XB9's use a de-stroked crank. The 9 pistons have a higher dome to maintain the same compression ratio which is why they raise the compression ratio significantly in a 12. I don't think the squirters make any difference...and Buell uses them, too. Thunderstorm heads are old school and the ports aren't as nice as the XB/04+ XL1200. The combustion chamber design is arguably superior, so many get those heads machined for use with Thunderstorm pistons. (Message edited by Rick_A on March 29, 2008) | ||
| V74 |
hey rick_a,when you say the "combustion chamber design is arguably superior"do you mean t/s or x/b ??? also what can be done to improve the porting on t/s heads,by that i dont want take them to your local head porter as an answer,i mean what is done to them ??? also how high compression can you go on a street t/s heads and whats the best way to achieve it ??? | ||
| Cjburr |
thanks guys for the answers. seems the "9" is used with the xb heads not the T/S heads, if he wishes to use the "9" pistons he will need the later model heads. I'm not quite convinced you should throw dirt on the old T/S heads just yet, seems they make comparable power to the XB heads till you go "Stage3" with the porting and even then they aren't far behind. Of course this is merely an opinion formed from looking at dyno sheets around the web and we all know that sometimes those are not attainable numbers for the majority of us. I'll assume that the later castings also suffered from some core shift making them a little less desirable to use......I'd like to see what Wes Brown could do with my original 98 castings though  Maybe someday soon, Chris | ||
| Rick_a |
The ports are better on the XB heads. The 15 degree squish combustion chamber design of the T/S's is superior. No doubt about it. That said stock vs stock XB heads have always edged out the T/S by a slight margin. If new heads are in the plan, may as well get the latest, greatest, and best, aye? V74, a good head porter will weld-up then reshape the ports to your application for a solid performance gain that's usually well worth the money. They also select a spring pack and setup clearances for your cam specs and valve sizes. As far as compression ratios, I've been told that generally 10.5:1 is the max at sea level and that 12:1 is the limit at higher altitudes. Of course that's dependent on other factors like cam specs, too...and there's good info on that here | ||
| V74 |
cheers rick_a,anyone out there know a good buell headporter in the uk,also estimate of costs - thanks |
