Ill check that next time I strip down the engine.
Ill also try your trick of injecting kero through the lubrication line to see if there is an improvement
ORIGINAL: frema
the back o ring is installed to prevent runnning the outer ring of the bearing in the shaft tunnel.
atleast thats what they say ,but i always take it out, i had never problems with it running without it
I think your preload is fine , i always test it , to push it on a scale ,and when the pressure is around the 4 kg when you feel the shaft move , then its oke .