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Old 10-20-2011, 01:44 PM
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rohmell rohmell is offline
Motorized Bicycle Elite Member
Join Date: Jun 2010
Location: New York
Posts: 1,533
Default I'm Kinda Glad They Use Cheap Steel in These Kits

I had a motorized bicycle come to me today for repair.
It seems that the owner did some cleaning and lubing of his centrifugal clutch, and when he went to re-install it, he broke the mounting bolt off flush inside of the crankshaft.
The owner was all upset, thinking that he now needs a new engine, or at least a new crankshaft.
I unmounted the engine, center punched a pilot hole and went in with a small drill bit on the drill press. I was amazed how easily that bit drilled thru the broken bolt. Nice, low quality steel, I guess. Did that twice more with progressively larger bits and then went in with a screw extractor. A few taps and the thing un-threaded no problem.
The broken piece of bolt had all messed up threads on it
Sent an M8X1.0 tap into the hole and chased and cleaned up the threads, good as new.

It seems that the centrifugal clutch removal tool with the fat end went into the first few threads on the crankshaft and messed them up, so when the guy went to reinstall the clutch, the bolt became cross threaded and snapped inside the crankshaft.

Re-installed everything, put a new bolt onto the centrifugal clutch, and sent the guy on his way very happy.

EDIT: Not glad that the guy had a problem, but glad that the cheap steel made it a breeze to fix everything back to normal.

So if you can, always use the clutch extractor tool with the skinny end, or else machine your fat ended tool into a skinny.

Last edited by rohmell; 10-20-2011 at 04:27 PM.
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