Can anyone explain how to check the gear box pre-load on the B box, and how
to adjust it if needed. It is in the Rotax maintenance schedule but is not
covered in my manual as to what it does, and how to do it.
To set the pre load on the gear box, you'll need a press, and a suitable
pusher that can straddle the shaft and press on the outer portion equally on
both sides of the gear. Compress the springs in the press with the pusher,
and remove the keeper ring halves. Release the press, and then remove all
the components, inspect, replace worn spring washers, and lube them up for
reassemble. If the pre load was extremely bad, you may need to use a fine
file around where the keepers pounded out the grove before the gear will come
off the shaft. When re-assembling, make sure you stack the washers properly, and
add a thin shim to the bottom of the stack-up. Try to compress everything
and install the keepers. If you can get the keepers in, then take it
back apart and replace the thin shim with a medium. If you can still get
the keepers in, replace it with thick one. Continue to incrementally
increase the shims until you can not get the keepers back into their slot, then
remove one increment of shimming, and install the keepers.
That's about it.
If it seems like a little more than you want to do, I can do it for you for $30 plus any shipping or parts needed. This check should be done every 100 hours, but is often delayed until the 150 hour service when the entire engine is inspected.
Authorized Repair Station for Rotax Engines