Ryan,


The crankshaft in MVVS engine is a push-fit into the bearings.
When disassembling the engine, after the con-rod is off the crank-pin, the shaft can usually be pushed back (out) with finger force.

The prop-driver sits on a split tapered collet. If this collet is not directly against the front bearing inner race, the crankshaft can move forward and back. The collet locks in place on the crankshaft when the prop-driver is pushed onto it, by the tightened prop.

You will probably see some scuffing on the backplate too.

When you buy a used engine, especially mail-order, you rarely know what you are actually getting...


Remove the back-plate and the prop-driver. Push the drive-collet back against the front bearing, while holding the crankshaft pushed forward (no need to remove the piston and the con-rod).

Now, reinstall the prop-driver and tighten the prop. Only the slight C3 bearing play should be evident. The shaft should have a very small (0.1-0.3 mm) free-play.


If the bearings are shot, this is a totally different ball-game...