'73 R75/5 LWB Rocker End Play Question?

[Tom H Ca]

I have read a bit on how to adjust the rocker end play clearance to cut down on valve noise. I have a clickingish sound when hot and over 3000rpm. It stays until it cools a bit and is mainly run under 3000rpm. Valves are properly adjusted and it's a clicking not a ping or the like.

So the question is....What is the measured clearance for the end play of the rocker?

On the side with the noise, the Ex play was about .0015" to .002" and the In was about .004". I loosened the top head bolt slightly and tapped the "block" down a touch. Now the In is at .0015".

The manual that I have says zero play, but the rocker needs to move freely. So how muck of a gap is that? Do I need to get the gap down to lets say .001" or even .0005"?

I have also read about upgrading the rocker and shaft assembly to a newer model. Is it worth it?

Thank you,
Tom

[barryh]

Yes BMW saying zero clearance but free moving isn't all that helpful especially as I found that the pushrods needed to be removed to check free moving over the full arc. The measurement I did was to check the gap with the a 1.5 thou feeler gauge which wouldn't quite fit so I assumed a 1 thou gap and was happy with that. 4 thou is definitely too much.

Some indication of what's acceptable can be taken from the later models which have shimmed rockers and I recall that there is a specified gap of something like 1 to 2 thou but you might want to confirm that.

[Tom H Ca]

Thank you for that info!!

I plan to ride the bike today and see how it sounds.

Tom

[Tom H Ca]

My adjustment may have helped. Traffic was a bit bad today, so paying more attention to it than the engine. I do think the noise was less if not gone. Will test again!

Tom

[gspd]

The rockers should have no perceptible vertical play at all. You can toss the feeler gauges for this job.
Providing all your adjuster threads are in good condition, screw the adjuster(s) in all the way to get maximum valve clearance. If the rocker moves freely in and out while you squeeze the blocks together, and after torquing to spec in stages, you don’t have to move it through its full arc. All it needs is enough clearance (.0001” ?) for a film of (pressurized) oil to seep out between the rockers and the blocks. Some people use clamps and other assorted devices to do this. Waste of time.

I just loosen both blocks, squeeze them together and tighten the nuts just snug. Then if necessary, tap them either way like you described. Be sure that the rocker tip is more or less centered on the valve, and the pushrod is more or less centered in its hole. Nothing critical here just be in the ballpark. Then torque in stages. The rocker tip (by design) is never dead on the center of the valve, that’s so the valves will rotate (supposedly).

Set your valves without feeler gauges? Tighten the adjuster until you can’t rotate the pushrod between your thumb and forefinger. That’s zero clearance. The thread pitch is 1.0mm. If you back off exactly one flat of the ‘hex’ (1/6 turn) you will have .1666 mm play. With a bit of common sense extrapolation you can go a smidgeon tighter on the intakes and a few smidgeons looser on the exhausts and you’re done. You can always verify your results with a feeler gauge. Eventually you will be able to just feel the play and know it’s fine. The exact numbers don’t matter. Too loose they clack, negative clearance they burn. As long as there is some clearance they’re fine. If these engines had suitable hydraulic lifters, they would have zero valve clearance and run great.

[Tom H Ca]

GSPD, thank you very much for that info. Some I knew and some was enlightening!!

I pulled the heads and barrels on my SWB manny manny moons ago to replace the pushrod to block seals and base seals and read up and used the clamp method to set the "blocks" and torque.

So, by what your writing, I "could"??? go a bit tighter on the rocker end play.

Geez, seems like BMW would have speced a measurable clearance???

Thank you!
Tom

[Ade B]

I just loosen both blocks, squeeze them together and tighten the nuts just snug.

After much internet 'research', this is what I did the other week.

[Rob Frankham]

All airheads up to 1985 were specified with 'no axial float but free to move'. You could probably interpret that as 'no measurable axial float but free to move'. For the earliest models there was/is a special tool to set the spacing between the rocker supports. If the (lack of) float can't be achieved, the rockers are considered worn beyond spec.

From 1985, an axial float of 0.03 mm to 0.07mm was specified. This was because a nylon washer was introduced between the rocker and the support to deaden any rocker noise. This was also the first year when shims were available to adjust the clearance. There's nothing to stop you using these shims to take up the float in earlier valve gear (although it's not recommended by BMW... who would rather sell you a new rocker assembly).

Setting the float on earlier valve gear to 0.03mm to 0.07mm will result in noisy gear (and extra wear).

Rob

[Kurt in S.A.]

A bit about rocker arms:

https://largiader.com/tech/rockers/

Kurt

[Tom H Ca]

Thanks again for the info. I had read about a service tool for setting the blocks.

I plan to get the bike out again today, I'll post if the .0015" did any good.

Tom