25 May 2003 - Today I cleaned and painted more engine parts. I have decided to send off the engine nuts and bolts to get them Cad plated. I started restoration of the carburetor. The photo below shows the carb disassembled.

27 May 2003 - Soaked carb parts in cleaner. Then used my Dremel tool with the small brush attachment to clean the various parts. The final step was scrubbing the carb body with medium steel wool. The photo below shows the finished parts.

28 May 2003 - Today I finished cleaning and reassembled the carb. Below shows a before and after photo

31 May 2003 - Today I sandblasted the fuel petcock.

7 September 2005 – My original aluminum slide has some pretty good scratches in it and was a little loose. I recently sent the worn slides and carb bodies from my wife’s R69S to Bruce Chessell of Triton Machining (http://www.tritonmachining.com) and he honed out the bodies and sleeved the slides. They turned out nice. I asked Bruce if he could do the same for my SUM carb on the R12 and he thought it might be possible. I sent the slide and carb body to him. He checked the carb body and it turned out it was nice and round. This was a good thing since he decided if it was out of round, he did not have a way to hold it in his machine to hone it. After he examined my slide, he decided to make a new one out of brass. It was a nice piece of work, quick turnaround, and works well. The photos below show the new slide next to my old one.

4 October 05 – I have been having problems with the carburetor such as rich running and leaking. After some examination I determined my original float needle was not sealing properly and sometimes flooding the carb. I had the needle turned down a bit in the hopes that this would help. It only leaked worse. I found a source in Germany for a new float needle and seat. It is going to take several weeks before I can get them in my hands. In the meantime, I hated the thought of missing out on some good riding weather. I had a carb rebuild kit for an R51/3 and it had a float needle in it. The needle was smaller in diameter and pretty long. I tested it in the R12 SUM needle seat and it seemed to fit well and seal the flow of gas off. I went about figuring how to make it fit into the SUM float. After some measurements I determined that a 5/32” (4mm) rivet fit perfectly into the float needle hole. I was also very pleased to discover that the diameter of the nail in the rivet was a couple of thousandths smaller than the R51/3 needle. So I cut the needle down to length, removed the rivet nail, and inserted the needle in the rivet body. Then the new needle went into the float and the carburetor was reassembled. A quick test of turning on the gas revealed no leaks. I started up the bike and all went well. I will do some riding this weekend to further confirm this fix. The following photo’s show the construction and fitting of the R51/3 needle into the SUM float.

Darryl Richman found a source for new float needles and seats in Germany. These are nice pieces of work. I now have removed the modification I made above and have a brand new needle and seat.

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