Motoscrubs.com

What is the use of this rubber?
It has contact with the rockerbody.
Something of an oil separator or guide?
It is missing on exhaust side, but should i care?



Thanks!

I think that the purpose is to try and stop oil flung off the camshaft from flooding the valve guides. Whether it works or not......


Cheers,

Colin

That's also my understanding (although I have found them to be missing on a couple of heads).

Ian

Perhaps it is to help lubrication for rocker and rocker arm pin?

As far as i understood, oil is delivered to the center of camshaft and exits at the base-circles of it.
So there is no direct pressured lubrication of the rockers.
Splashing oil is catched and runs all over the length of the rockers and floods the centerhole and the sides of them.
Is this correct?

So it would be a good thing to have these rubbers in place...

Somebody facing problems because of missing rubber?

Possibly, although the vee twins do not use these rubbers and their heads are basically the same.



Colin

I always 'assumed' the rubbers were there to direct oil splash from the camshaft onto the rockers and their spindles, I can't really see any other use for them? I also have often found them to be missing.
Cheers, George

Are there known defects of rocker bearings due to missing rubber?
I dont think so, but what do i know...

These rubbers are available and are cheap, shipping will be more expensive for a single part.
So i will keep an eye on it and try to find some raw material.
Should do a penetrating test with it before installing.

I think they are there to direct oil into the rocker and they may possibly damp a bit of noise. The covers on a single are larger than the twin and they probably act as a nice shell like amplifier of rattles from the rocker gear. I wouldn't stress about them being missing, I've never used them in any of my own engines and never used them in any race engine that I've built in about 35 years. This has never resulted in any noticeable wear or any other issues, aside to a bit more noise maybe.

Regards Nigel

This is the best answer!

I would add they are just cut from 4mm nitrile rubber sheet.