Odd crankarm problem



Nukuhiva

Well-Known Member
Jul 14, 2004
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My daily beater is sick. The bike is a 1970's/early '80's (probably) issue KHS 10-speed, very confortable, perfect size and geometry for commuting, so although the bike may be a cheapie, I'd like to keep it around. The cranks are slightly unusual insofar as they are held in place by cotter pins and they have a little ridge inside them, which slides into as keyway in the bottom bracket axle. The guy at the bike shop worth going to for vintage bikes says he's never seen one like that. The left crankarm has lost said ridge - eaten away by decades of being cranked, no doubt - and CANNOT be tightened by cotter pin alone. No matter how far you drive the pin in, no matter how tightly you screw it shut, it wiggles loose almost instantly. The right crankarm is fine, solid as a rock. The aforementioned guy at the bike shop says that's impossible, cotter pin should be enough. It's not. I've finally given up trying to fix what I have - too many failed attempts in too many different ways - and resigned myself to the fact that I will probably have to replace the entire bottom bracket plus crankarms, hoping I can find one that fits... This bike did seem to come with a host of components no one has ever heard of, the shifting system was rather unusual, too, didn't even bother trying to find replacement parts, just changed the whole thing. Anyone have any better ideas?
 

oldbobcat

Well-Known Member
Aug 31, 2003
3,233
194
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If you and your bike shop can't find a cotter to hold your cranks, then it might be time for replacement. When nobody makes cottered cranks anymore, cotters in different sizes become harder and harder to find.

Personally, I gave up on cottered cranks 40 years ago.

You need a double-chainring 8-speed crankset, because 8-speed chains are widely available and compatible with your 7-speed setup. Origin8 makes reasonably priced quality components for keeping old bikes alive and serviceable. Here's a crankset that your dealer should be able to order for you from J&B Importers. http://www.jbimporters.com/web/checking_product_description.php?part_number=22551. You can also shop online.

Inexpensive sealed JIS square taper bottom brackets are widely available for about $20-30.