Rocker arm regrind

[SteveD]

With wear and pitting, should this morph towards a discussion of zddp?

[ME 109]

With wear and pitting, should this morph towards a discussion of zddp?

Well then, I've been using Penrite HPR30 20/60 for twenty years. Full zinc 1660ppm. Cam and followers are excellent for approx 280,000 ME 109 K's



I did have the rh cover off @2,000 k after grinding, for a weep from the cover. Took the opportunity to back off both adjusters sufficiently to use a light, magnifying glass and a mirror to carefully examine the ground surfaces. Unremarkable.
But that's only 2000 k.
So little material was removed during the grinding process. Inspection after each pass on the dance floor ensured the minimum was removed to clear the facets. That was two or three light passes each rocker.

Here's the reason for fitting the new rockers, sort of 'while I'm in there' thing.
Worn out timing chain clip, three years old. Too much redline.

[George Ryals]

I say, put your reground rockers in and run the piss out of for a couple thousand then take a look. I predict full success with your regrind and polish!

[khittner1]

.

Here's the reason for fitting the new rockers, sort of 'while I'm in there' thing.
Worn out timing chain clip, three years old. Too much redline.

Pretty much confirms my thoughts on the "boxers love to be revved" nostrum . . .

[enigmaT120]

If you let them sit and idle, oil stops going to the timing chain. Maybe there's somewhere in between idling and red line. We'll just never know.

[George Ryals]

At idle wouldn't there be plenty of oil coming out the fronts of the cam and crank bearings to keep the chain and sprockets lubricated?

[SteveD]

If you let them sit and idle, oil stops going to the timing chain. Maybe there's somewhere in between idling and red line. We'll just never know.

I can't recall where I read this and I can't account for the difference either, but pre 80 preferred idle is not less than 1000rpm, post 80 is 1100rpm to ensure oil to the cam chain. Would that be right? Really though, does anyone leave their bike idling for very long?

[ME 109]

This little spring loaded piston lives inside the 'pressure relief valve' which is at the top of the front bearing carrier. It's the horizontal tube seen in my previous pic. Not to be confused with the oil filter 'bypass valve'...........
The relief valve supposedly opens at 70 psi according to my bmw manual. I suspect that may be fully open at 70.
The little bevel on each side of the piston is the way the chain gets oil at lower rpm, I reckon.
These bevels line up with the two outlet holes of the relief valve. I think these bevels allow for x oil flow before the relief valve fully opens. I can't think of another rerason for the bevels.
The relief valve outlets are directly over the cam chain.
There are four, approx 5mm diametre holes in the valve. Two at either end. The holes closest to the threaded end are the main outlet holes. I think the holes at the other end are to drain any oil that gets past the spring loaded piston.

I don't know how much oil comes from the crank bearing and cam bearing, and what roll it plays in oiling the chain. The spring and piston type cam chain tensioner needs oil to be flung from the chain to supply the reservoir, so there must be some oil flow through the relief valve as well at lower rpm. Oil may also pool at the bottom of the timing cover as it flows through the two return holes to the sump. This would oil bath the chain, possibly.

The relief valve in my picture is actually bent upwards at the left end, from when the parted chain hit it. Luckily I smelled a rat and removed the bent valve, only to find the piston jammed in the bore. Would have been interesting to see what happens with a stuck closed valve!
Fortunately I had a spare valve and swap it in.

[Rob]

Fortunately I had a spare valve and swap it in.

Never throw away (or sell) anything.©

[SteveD]

The relief valve in my picture is actually bent upwards at the left end, from when the parted chain hit it. Luckily I smelled a rat and removed the bent valve, only to find the piston jammed in the bore. Would have been interesting to see what happens with a stuck closed valve!

Shouldn't you just whack it back to horizontal?