Are you saying then that a crank on a 21 for example should only be expected to last between 15 and 20,000 miles before it needs a re-build, bearings, etc?.

That doesn't seem a lot? - but I freely admit to not being an expert! (

What would be the anticipated cost of a bottom end re-build on a 21?.

It's just that most second hand 21/28's come onto the market with between 15 and 20k miles on the clock - and if one were either buying or had just bought (as in my case) a machine with this type of milage, it could potentially cost quite a bit of money to do.

Regards - Ewan (Fifer)