Final Drive Oil - GL4 or GL5?

[BuddingGeezer]

I decided to change mine a while back....I had ridden the bike 15K and was unsure what had been done prior...
So I poured some Mercruiser 80-140 into it, figuring that the folk at Mercury would want some pretty substantial oil in the final drive.
Have fun!

Why would one want to put 80-140 weight oil when the specs are 80-90?????? BMW dealers were selling 80-140 GL5 synthetic when the factory speced 75-90 synthetic. A larger % of the 80-140 final drives failed compared to the final drives using 75-90. The BMW MOA tec guru's theory was the 140 was too thick to properly lube the bearings in the FD. I memory serves, BMW bulletined the dealers in North America to stop using the 80-140.

I know a Honda FD isn't a BMW FD, but 140 is way outta spec. Just saying.,

Nothing wrong with using GL5 lower unit oil just don't use Yamalube lower unit oil. It's speced GL4.

 

[dwalby]

A larger % of the 80-140 final drives failed compared to the final drives using 75-90.

The sad part is that enough drives failed with either lubricant that they could actually compile a statistical comparison. So much for the propeller brand. I remember being at one of the few BMW auto/bike joint dealerships at the time, and seeing what looked like a brand new bike with the ***-end removed I said to the mechanic, "so they ship them without the final drive attached and you guys have to assemble them upon delivery, huh?" He said with a bit of embarrassment, "no, that one has 5k miles on it and the rear end has already failed". So much for the mythical Teutonic engineering talent.