Crank pins

neil cairns · Post by **neil cairns** » Fri Jul 28, 2006 9:38 am

I have just completed the re-biuld of my 18S engine. Its crank pin sheared off clean, on the timing side two weeks ago, just as I completed a run with the Bedfordshire VMCC ( Albert Brown Run.) The AJS is a combination, and works had. The crank pin I found inside the engine was a solid billet item, with 90 degree corners, and it is easy to see where the crack started. I have now fitted a club two-piece item. I remember some time ago something about AMC crank pins being dodgy. Some one mentioned pattern pins by Ajax? or Atlas? or was it Alpha? Did someone back in the 70s-80s rebuild the engine, thinking it would not get much use so fitted a cheaper item?

NC.

itma · Post by **itma** » Fri Jul 28, 2006 10:48 am

Its the pattern bits that were/are dodgy not the AMC two piece item, not even the smaller diameter pin was iffy.
Vast amounts of words have been expended on this very subject over the years.
Wash your mouth out or Janet will come round to confiscate your bike

m knight. · Post by **m knight.** » Fri Aug 11, 2006 10:26 pm

m knight. · Post by **m knight.** » Fri Aug 11, 2006 10:28 pm

Get your crank rebuilt by Mr Saggers with a B.S.A crank pin, then it will last forever & you can sleep easily!

Biscuit · Post by **Biscuit** » Sat Aug 12, 2006 10:31 am

In all probability the crankpin was not pulled up tight against the flywheel, lacking the correct equipment, I use the crankpin nuts to pull the pin in to the flywheels, doing this, one has to be very careful that the pin is indeed all the way home. I would think in this situation, ninety degree corners, ie. lacking a radius, is not relevant.