Just a warning about the shim , it should be on the pto end of the crank and not the flywheel end.
You shim the PTO (blade) end instead of the flywheel end because on a vertical shaft 2 stroke.
The major thrust loads and wear happen at the PTO end The flywheel end is relatively stable and lightly loaded axially Shimming the PTO side keeps the crank positioned correctly under real working load
When spinning, the blade creates: Downward axial load (from gravity + airflow lift effects) Up/down thrust from cutting impacts Gyroscopic and vibration forces
All of that pushes and pulls on the crankshaft at the PTO end, not the flywheel end.
Over time, this causes wear on the lower crank face and bush/bearing surface.
When you shim the PTO end:
You take up the slack right where the wear occurred You re-center the crankshaft in its natural running position You maintain correct: Bearing/bush alignment Oil film clearance Crank stability under load
A lot of the motors I have, have so much end float the flywheel starts to rub on the coil plate , see image below.
So it always pays to lift the crank back up a bit to compensate for wear.
Make sure the round shim is a fair bit smaller than the bearing.
So why still not full size?
Even though it’s a ball bearing, lubrication still matters because:
The inner race isn’t sealed against the crank Oil/fuel mix still needs to: Get between shim, crank, and bearing surfaces Prevent fretting and galling at contact points
If you used a full-size shim that completely matched the bearing face:
You could trap oil out of that interface Create dry rubbing surface between bearing and shim Increase heat and wear on: Crank face Shim Bearing inner race side
You want the shim:
Slightly larger than the crank shoulder, but smaller than the bearing inner race
Inner diameter (ID): Close fit on the crank (not sloppy, not tight) Outer diameter (OD): ~1–2 mm larger than the crank shoulder Still clearly smaller than the bearing inner race
I had a damaged crank the other day, flywheel side , worst one I've seen on a victa that's still together in one piece, they must have run the motor with a loose flywheel.
