It appears you're interested in specifications for the BMW R51. This Allround model is powered by a Two cylinder boxer, four-stroke engine with 494.00 ccm (30.14 cubic inches) of actual displacement before 6.7:1 compression. Fueling is metered via Carburettor. Amal allowing this machine to produce its 24.07 HP (17.6 kW) horsepower and torque. According to our records engine heat of the BMW R51 is moderated by Air. You'll need to get familiar with the 4-speed transmission and pay attention to final drive Shaft drive (cardan) maintainence. Our best information shows that the front tire size is 3.50-19.00 and the rear is 3.50-19.00 . The entire package is supported by the frame, Steel single cradle. We know you like to go fast or cruise all day, but when you need to stop, you'll be dependant on Expanding brake (drum brake) front brakes and Expanding brake (drum brake) rear brakes. The BMW R51 was launched in 1939, and we're happy to know (or assume) you've got one in your garage. To help you keep your ride in tip-top shape, consider purchasing an owner or service manual.