Cast crankcase vs extruded one.

Yes, the KB crank will fit.

If you have a lathe you could bore out a case and use some copper or brass tubing, shrink it in, and make a new bearing that will be 10 or 100 times the durability of the original anodized aluminum.

I won't call it "easy" but it is a straightforward process. The difficulty is the precision.

Phil

pkrankow wrote:If you have a lathe you could bore out a case and use some copper or brass tubing, shrink it in, and make a new bearing that will be 10 or 100 times the durability of the original anodized aluminum.

I won't call it "easy" but it is a straightforward process. The difficulty is the precision.

Phil

Hi Phil,

I would favour using phosphor bronze as the bearing material but it is a little expensive.

Copper or brass will work fine but copper tends not to last very long - it tends to soften "anneal" as it heats up.

Provision also needs to be made for lubrication. The standard crancases (cast and extruded) have a groove to lubricate the crankshaft. This should be reinstated in the bearing.

I tend to not use a single tube the full length of the crankshaft but use two smaller tubes. Then for the difficult bit - I drill a hole at an angle from where the base of the cylinder head fits to the gap between the two bearing tubes so that this does away with the need for a groove and lubricates the gap between the two bearing tubes.

Ian