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i have a 1980 shovelhead with early evo flywheels. It ran great most of the season and then lastnight on my way to the Davenport swap my bike quit... i cracked it open this morning and the pinion shaft was sheared off.
The shaft was jammed into the cone but i think that happened after it broke and the uneven surface jammed it in there.

i believe that it was oiling just fine. i was still getting oil to the top.

why? how? anybody?
 

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I've seen it prolly 3-5 times before. I have no idea why, but I'd guess it's case/bearing misalignment thing or maybe a pinion bushing that's a bit too big I.D. Also might be from dirty tapers or overtightening the pinion nut. All you can really do is re-line hone everything (lap the pinion race and line ream the new bushing) and then carefully reassemble it all. I have just slapped in new cranks (at customers request) but I have no idea how long it lasted. After trying to talk them into line lap/reaming, they prolly weren't in a hurry to come back tell me if I was right, I'd guess.
 

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The 100ci Power pluss Indians had the same problem, bad pinion shaffs, Made by Tiwan Ted, get good ones by Jimms.

....Roach.
 

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Dragstews: good call on the reversed pump-gear possibilty, I didn't think of that (not that I'm an expert). Barring a quality control issue most of the broken shafts I've witnessed I have attributed to poor trueing technique. You can line-lap all you want, but if the wheels aren't spinning concentric or parallel it doesn't matter. A lot of people smack em' between centers, but don't have the proper "feel", I tend to think this one of the major causes of pinion-shaft failure. Just my humble 2-cent opinion.

Jerry
Rhode Island
 
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