B40 crank “end-float”

[Stubaker58]

Sorry to be a bother, this is my first venture deep into a unit single.   I have got over the nightmare that revealed itself when I got to dismantle the (newly built) bottom end. New (ie different) crankcase and a different crank assembly later!  The sludge trap is cleaned out and I've got new bearings etc.

I would like to avoid a further strip down if possible so I'm going to take things slowly. Now I'm used to Bantam engines and I'm happy to calculate the shims needed by inserting the crank, bolting up the cases and pulling and pushing whilst using a dial gauge to measure the difference.

Now I understand that in use the B40 crank is fixed but that nonetheless some clearance (4 thou?) is needed to allow for expansion. I have a cunning plan and would like to know whether you think it will work ...

I've lightly ground the inner diameter of the old, knackered, main bearing  so that it is a nice sliding fit on the crank journal.  My intention is to fit the bearing into the left hand case, the bush into the right hand case, fit the crank and then bolt it up. As the bearing is now a sliding fit there should be some actual end-float which I can measure and shim accordingly.  I'll then remove the modified bearing, fit the new, tight, bearing and assemble the cases using the proper puller and hopefully progress on to the gearbox.

Any thoughts?  Thanks

[Spaceman]

That will probably work but it will depend on how easily you can slide the crankshaft to and fro. The alternatives are either to add shims until the crankshaft just nips up and then remove 4 thou or to measure the clearance via depth measurements in each crankcase half and a measurement of the distance between the crankshaft shoulders.