Forum bmwbike.com

I have a bike that have bigs valve covers, carbs and air intake, but the block number is 645...
can I know if the cam shaft it's from R69S or from R50/2 before to disasemble the bike?
May I use the compression ratio or other way to know it?

That block number is for R50/2. If it has S type valve covers, carbs and tubes, then the bike has more likely become an R50S than an R69S.
If it has S type valve covers, then the heads must also be S type. You can check the carb numbers to see if they are for S type. I don't know how to check the compression ratio or the cam.

The covers are S type, but are not 50S, that are smaller.
Thanks you.