K Bike Tech

How Much Clutch Spline Lube Should I Use?

As much as you want:

Here's how much I typically use:

A common wives' tale among K bike owners is that you need to be sparing and put a precise amount of lube on the transmission input splines when lubing the clutch splines. Otherwise the lube will supposedly spin off onto the clutch friction surface and foul the clutch plate. This is simply NOT TRUE.

Here's why:

Basic physics. The rear side of a K bike clutch plate has a raised collar.

That collar is there to provide a larger surface area for transmitting power from the cutch plate splines to the transmission input shaft.

When the transmission is installed any excess spline lube gets squished out to the rear lip of the collar which is behind the rear outer surface of the clutch housing. The first time the K bike is started and the clutch assembly spins up any excess spline lube spins off radially onto the inside of the bellhousing which is harmless.

However, it should be noted that, as shown in the first picture above, the front face of the transmission input shaft should not have any excess lube on it because that can spin off onto the front clutch friction surface and possibly foul the clutch.

This approach allows application of the maximum amount of spline lube without causing any issues.

Empirical evidence:

I've spline lubed in excess of 30 or 40 K bikes like this over the years and never had an issue. When I take them apart later I do find a little spin-off lube on the walls of the bellhousing as expected.

Recommended Spline Lube:

Beemershop TS-60:

https://www.beemershop.com/product/ts-60-spline-lube.html

Related page links:

Splientology.pdf

Clutch Spline Lube

Clutch Work w/o BMW Special Tools