We have highlighted a few BMW motorcycles that can be considered Classic Sports Bike. The R69S and the K75RS are both Bavarian for Sports Bikes, but this 1965 R27/2 offered up on eBay now was never considered a sports bike. It was a 250cc single cylinder work horse that got you around town, and could even drag a side car around, very slowly, if you wanted to take a passenger. But having just returned from Bonneville, I have first hand experience with a BMW single setting multiple land speed records.
From the seller
BMW R27 Original condition,, some dents, some rust, needs tool box hinge repaired, headlight re-wired, starts and runs fine, carb float needle will flood from time to time, vibration will cause float to slide up on stem.
From the factory the R27 was given a 68x68mm bore and stroke to give it it’s 247cc. A 8.5:1 CR piston fed by a 26mm Bing carburetor would generate 18hp at 7400rpm. This was claimed to push this single to 80mph, but if you wanted to pull a side car, the speed would drop to 55mph. These numbers might be a little on the generous side. I have heard from riders that they are able to get these little single up to 70+ mph, but it takes a while.
To prepare for Bonneville, some of the changes that were made to the record holding 250cc BMW were classic hot rod’er tricks. Cam, Carb, Compression. Believe it or not, BMW offers a sport cam straight from the factory, so you will be able to get the lift and duration you need when adding compression and larger carburetors. Brooks Motor Works ran a 38mm Dell’orto carb on their Vintage racer, so this lets you know that it is possible to add bigger carburetors to get more out of this little engine.
To increase the Compression ratio of this little 250cc R27 there will be a few options. I am not sure, but I believe that the 500cc pistons from the R50 will be a direct fit (wrist pin height may be a problem) so that opens you up to the R50S high compression piston. And there is word around town that you can increase the bore of these little singles and push them out to almost 300cc.
This may have come from the factory as an around town, people mover. But as land speed racing has shown, there is a lot of room to improve this 1965 R27, making this 250cc motorcycle a great platform to create something that can compete as a sporting single. This bike already comes with an aftermarket muffler by Earnst Hoske, a former BMW racer turned performance parts manufacture. I wouldn’t call it half way, but it is a start. BB