1 75w90 vs 75w140 / dino vs synthetic gear oil for '91 k100rs 4v Tue Jun 12, 2012 4:27 pm
browe58
active member
bought bike a fews weeks ago w/ 86k miles. on the ride home a few times i had trouble going from 1st to 2nd, kept going into neutral. not sure what grade oil was in gearbox but i changed it out immediately w/ 75w90 synthetic blend. shifting was much better for a while. it was actually siky smooth but 1st to 2nd required precise shifting. then i started to have false neutrals going from 4th to 5th so i thought it didn't like synthetic blend so i changed it to 75w90 dino. shifting was no longer silky smooth but klunky & positive like most bmw's because of the dry clutch. but i kept getting false neutrals from 4th to 5th. i don't think it's a spline issue as it downshifts silky smooth in all gears and in all speeds. and if i preload the foot shifter prior to shifting from 1st to 2nd and 4th to 5th it always goes in w/ no problems but i've never had to that w/ any other bike. just seems like a lot of work and thought process to shift "the ultimate driving machine". anyway, i read on one of the forums that bmw later recommended 75w140 synthetic for the gearboxes. so i tried that and noticed no difference. it's easy to change out but i'm getting tired of doing this. i thought i'd try one more time...... a straight 80w or 80w90 in synthetic as the 75w90 in synthetic blend seemed to work best. in the end, if i have to live w/ preloading the foot shifter prior to shifting from 1st to 2nd and 4th to 5th it's not the end of the world. but ideally, i just want to shift naturally without having to think too much about it. is this normal for the k's???? any suggestions or thought? thanks.
Bill
Bill