Distributor cam advance repair

[steve10909]

I overtightened the nut securing the distributor cam advance mechanism to the end of the camshaft, and snapped off the threads. Has anyone repaired this by tapping a new bolt into the end of the cam to secure the advance mechanism? Are there any other solutions short of replacing the camshaft?

[Bobmws]

You would have to be dead center when you drilll & tap. I expect the cam shaft material would be hardened(unlike the new K12s!), making the task even tougher. At this point you have nothing to lose by trying. Good luck

[steve10909]

Bob,
Thanks for the reply. I hope that you're wrong about the hardened steel. The exploded diagram for the /6 cam in the parts manual shows that it's actually in two parts held together with a woodruf key. The timing end appears to be malleable. I've smoothed down the rough spot where I broke off the threads with a file without too much trouble.
The options I'm thinking about now are whether to drill & tap with the engine in the frame, or taking the engine out of the frame and bring it to a machine shop to drill & tap, or taking the engine to the dealer to replace the cam. (I don't look forward to taking the engine out.)
If I do take the engine out, I'll have to look at the oprtion of buying a used engine. It might be cheaper than paying for a new cam and the labor at a dealer. The bike is a '76 R75 and I can't justify sinking $1200 into it.
Steve

[Bobmws]

Steve,
Consider doing it yourself. Surely there are some savvy airhead folks in your area. Try www.airheads.org for some contacts. I've seen these guys rebuild an engine at a rally on a picnic table!

[Markst1]

you might try this person who, I believe sells a tool to repair this exact problem:
repairhead@sbcglobal.net

[steve10909]

I sent a message to "repairhead" and I am waiting for a reply. Your note also got me thinking about how I would make a drill bit guide that would center a bit over the end of the camshaft and guide the bit as I apply pressure to the drill so that the hole is coaxial with the central axis of the camshaft. (Now all I need is a machine shop to fabricate it.)
Thanks a lot, I may be able to save my engine after all.

Steve
In Northern Virginia