This is one of those things I try to do to every BMW motorcycle I rebuild.
This area is cracked on nearly every frame I tear down. It is the rear foot brake area which also is the muffler / silencer hanger, and where the passenger foot pegs attach. This frame is a 1978 BMW R100s. If you are considering rear sets on your bike that attach to this section, then I HIGHLY RECOMMEND doing this procedure.
cracked tab near rear foot brake pivot hole on BMW airhead framecracked tab near rear foot brake pivot hole
cracked tab near rear foot brake pivot hole on BMW airhead frame
New piece of metal to weld onto the old cracked section to reinforce the area making it MUCH stronger and no longer prone to cracking.
Welded metal onto the rear foot brake section of a BMW R100S
Finished powder coated frame with the welded metal. This area is out of sight to most people unless they take the rear tire off.
Fingers crossed this exhaust works. It is from a 1930’s R12 BMW. I had a larger inlet welded to mate with the R75 headers. I hope they do not restrict power in any way or make the tuning of the engine difficult.
The headers and mufflers connect OK and luckily the brackets on the mufflers line up pretty close to the exhaust hanger area on the R75/5 frame.
To connect the muffler to the frame, I had to make some custom brackets to attach the muffler.
I made a test set out of aluminum and everything worked out OK. My holes were slightly off but I corrected for that later.
Here is the test fit.
I took my brackets and a pocket full of cash to a local welding and machine shop. He replicated my brackets with stainless steal and put the holes in the correct place as per my instructions.
Stainless steel should withstand the heat, elements and keep its shape. I worried that the aluminum brackets I made would not do any of the above.
Here is the bracket attached to the frame:
There isn’t much room to work with in there but with the right nuts and bolts, everything went to together just fine.
Got the Shorai battery and luckily it fits under the tail section as I had hoped. It only weights about 3 lbs so it shouldn’t be a weight issue. It will just be a matter of running the wires in discreet places.
I bought some aluminum to make a cage and bracket for it.
I cut the two ‘L’ brackets to create bumpers from preventing the battery from moving forward or backward.Then started bending the aluminum strip to make a srtap like bracket to hold the battery from moving left/right or uo/down.
I marked the footing and drilled some holes. I purposely offset the bracket to not interfere with the outlet on the battery for the Shorai battery tender.