Originally Posted by supershaft
I wouldn't worry about valve seats or circlips. The later trannies have other mods that I think are a big improvement. The valve seats sometimes last as long as any. Heads with 40mm carbs have monster big ports. I think they are border line too big and not the best shape.
Smoothness? Even my dad liked the R80 for it's smoothness. Personally, the main thing I notice about them is the lack of power versus a R100. They have always reminded me of a R90 that way. Why not go bigger than 94mm bores? Personally, I think BMW stopped at 94mm for a lot of very good reasons. I think BMW thought they went too far at 94mm. I think they took it as far as it makes sense to go.
Just the input I was hoping to hear!
Port-sizes are where my knowledge drops off significantly. So do the post 90's R100's have the 40mm ports? Are these what people put the larger European Bing's that I've read about here and there?
The main reason I've jumped to this is that my local BMW scrap heap (Repsycle) had a few nicely priced R100 short blocks on my last visit. I just want to be sure I'm not taking 2 steps forward and 1 backwards and mostly that it's a good solution.
Do you have any knowledge on how easily the R80 trans would mate to the R100 block? I'd love to have that extra power you (and many others) feel is missing off the bat, using BMW parts.