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To keep the streak going I finished the clutch cap on the lathe today.  The first milling operation went smoothly but this lathe operation had a slight bump or two in my way.  I initially programmed the part using conventional tooling but the recessed pocket really needed some more specialized face turning cutting inserts.  The problem was minor and did not cause any undue headaches but the program needed to be redone.

The first step was to cut some profiled soft jaws to hold the part:

The small burrs you see are away from the profile and will not cause any clamping problems.

Unfortunately I was on such a roll I machined all 3 parts without taking any pictures of the process!  Here’s the final 3 pieces looking really good:

The clutch side is nearly complete and looking great.  I’ll try to get to the oil fill and crank end plugs today then next week I have to do a bunch of contract machining so will likely be too busy to make bike parts.  Damn.  I will try to get to something done to keep the streak going.

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  • GrahamB

    Chris, I'm blown away by this project.

    Just a curious question, did you calculate a weight for the finished motor? Does it end up lighter than a production motor, or does the strength needed for extra power and an extra cam-drive bring it back up past a Honda etc etc 600?

  • coseng


    Thanks, hopefully so will the competition….

    Motor should weight 100-110lbs including throttle bodies and electric start. That is comparable to a production 600 I4. I ended up with a bunch more aluminum in the cases (sand castings are not as easy to cast thin walls as permanent mold) and a bunch less in the shorter crank so it almost cancelled out. I'd rather have heavier castings and a shorter crank any day. More rigid castings and less gyro effect and rotating mass to spin up.

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