Frankenkrauser GS- A krauser engine desert BMW

KRAUSER : In the early 80s Michael Krauser developed a kit for the bmw boxer engine. The kit primarily consisted of a new 4 valves head designed for such engine. The kit was used in racing events and in sidecar racing where BMW won a lot of championships. I have seen pictures of dakar bikes which raced the early years with this set up, and I wanted to learn personally about it. Hence, the construction of bike with suck a kit.

 Picture shows the custom handmade frame which allows the engine to be mounted tilted on its axes. 

Such method does well to the angle of the shaft connection to the transmission and should ensure shaft longevity. The set up is the classic elongated double swing arm with 2 WP shocks and a Marzocchi 45 mm Magnum in the front

 Picture shows the extensive breather for the krauser engine and the handmade seat pan. Note the engine mounts in the middle of the frame.

Other side of the bike. While I am working on the engine, I am debating as to what fairing and front end to use. Do I go with a Marzocchi M1 that was used during that period or do I keep the magnum with the wave disk. It looks kind of weird on this bike, I must admit.

Picture shows the tank used in the first dakar races. Such tank is made of fiberglass an it has 2 compartments with 2 separate gas lids for fuel. The acerbis dual light Afrika fairing seems to fit with the motorcycle.

Engine-

Two pics of the R crankshafts. The one on the right is the modified crank that I will use with the Krauser engine. Both cranks are from the stock long stroke R engines. The modified crank has been drilled, its shoulders cut and made it lighter. Such crank should work better on my engine making a fast revving one. Note the difference in weight between the 3 cranks

Next I balanced the conrods. I was surprised that even if the 2 rods had a small difference in weight, when they were balanced on the right scale where each piece was weighted accordingly, I found a difference of almost 10 gr.  It was too much for my taste. They are now down to a .5 gr difference. Last I balanced the pistons which coming from Krauser  I expected to be were very close. In fact they were so. I just ended grinding a bit one pin to make the difference null.

First I installed the mounting rods in the block maintaining the lenght specified on the krauser maual. Then the connecting rods with new bearings and then installed the pistons plus the cylinders. Note the pistons with the marks for the 4 valves. I forgot to mention that the pistons top as the skirts were treated with special coatings to ease the heat.Picture shows the back brake line and the back alum racing muffler .Finally it is coming together. The stand needs to be modified as well as the exhaust pipes mounts. I will probably install a thermostat since I have already a larger pan and I dont like the oil being too cold.

FUTURE ACKNOWLEDGEMENTS:

Chris in Texas for being the BWM guru and best welder I ever met

Jim at MAP engineering for making the front brake adapter

Gianni and Adriano in Italy for the their suggestions on how to make it more reliable

Finally Sven Erik for sharing his experience on his own bike