R1150GS - R1100S Cylinder heads and pistons?...

[DrAlf]

Following on from my early thread - I've now taken delivery of a load of R1100S bits. Gas flowed cylinder heads, pistons and barrels. All look to be in good condition. I have an engineering firm lined up to convert the heads to twin spark but before I start this - has anyone here done this already?

My assumption is that I don't need the barrels and can just use the heads and pistons and that they'll be a direct fit.

Is this right? Advice appreciated. Must go faster. Ta..

 

[PaulRS]

You also need the barrels, because of the smaller bore on the 1100 engine, 99 vs 101 mm.
What about cams? You got the 1100S cams with the heads?
The extra power the S makes is from higher compression, AND different cam profile.

And why bother with the twin spark, imo there's no gain in that, (except emissions) the oem plug is already nicely centered in the combustion chamber.

Paul.

 

[DrAlf]

Thanks Paul and you are correct. 99mm bore on an 1100 and 101 bore on 1150 means you need barrels, heads and pistons. On an 1150 you'll lose cubic capacity but gain performance via compression - at the cost of bottom end. Point to note, and despite my assumption, you cannot convert single spark heads to twin spark. I'll either be looking for an 1100/1150 single spark project bike shortly or selling a shed load of go faster bits!..

 

[uncle dick]

Didn't the 1100S have stronger conrods to cope with the increased rpm?

 

[Ijustwanttoseethephotos]

R850 to R1150, same part number.

 

[DrAlf]

Apart from compression, its all in the cams. Interestingly early r1100 bikes 93 - 95 had bigger valves than later bikes 95 - 06.