Cylinder Head Confusion: R65 vs R65LS

[Boxer_Bolshie]

Okay so I am confused.  

A month ago I picked up a second set of heads, however one seems to be from an LS as the combustion chamber taper is different (two step) rather than the R65 (three step).  I figured this meant that the compression ratio was higher for the LS and so called a local expert who confirmed my suspicions.  BUT when I checked the specs for both bike's at http://www.bmbikes.co.uk/bmwmodels.htm they say that the compression ratio for both bikes is the same at 9.2:1 and after 1981 both have 40mm intake valves...

So what am I missing?  

Why are the heads different?  

What are improvements in the two step combustion chamber for the LS?

Would there be any improvements in a head swap to the LS?

Should I personally get a head swap?

Anything else I should know?

[Bob_Roller]

The LS cylinder heads are the same as the standard R65 from the '81 model year, to the end of twin shock production, the LS version was just a styling exercise, no engine differences .

The only major change to the twin shock bikes cylinder heads (as well as about a hundred other small improvements on the bike), was starting with the manufacture date of 09/80 and continuing to the end of production .

The valves are 2mm larger, than the '78-'80 model year bikes, the 'first generation' R65's .

I believe also that the first generation had two piece valves, there were some problems reported with valve failures .

[Boxer_Bolshie]

Turns out this can't be an LS as the intake valve is 38mm which was changed to 40mm in 1981 (as you mentioned).  So I was sold pre and post 1981 heads thinking they were mates (nothing saying what year they were)... but I "ASSUMED"  (ASS out of U and ME in this case just me) they were mates.

[nhmaf]

Sorry to hear of your problems - it shouldn't be this hard or painful to get a new set of heads.   One has to be keenly careful of stuff selling on ebay and CL these days.  Hope that you get your $$ back or the seller makes it right for you.