Valve covers

[JohnT]

My R100R with the round covers is noisier than my old R80 and yes I have set the valve clearances.
I read somewhere that the later 'square' valve covers were a sound deadening fix by BMW. Is that correct?

[Rob Frankham]

I think that's an old wives tale... The change from 'rounded to square covers was just a style change to give the engine a 'more up to date' look for the 70's.

A couple of thoughts...

Have you checked the axial play on the rockers? Late engines are shimmed to reduce noise and the play needs to be checked with a view to re-shimming if the play increases.

Does your engine have the 'anti ringing' inserts between the fins on the cylinders?

Rob

[SteveD]

Out of curiosity with..

Great question — and a bit of a nuanced one too, so let’s unpack it.
The switch from round valve covers to square valve covers on BMW airhead motorcycles (which started showing up in the early 1980s with the R80G/S and later models) wasn’t primarily about noise reduction. It was more about modernizing the look and making the covers slightly stronger and easier to produce. That said — there can be a small difference in perceived mechanical noise, but it’s marginal and usually not the main reason for swapping between them.
Here’s why:
Valve cover shape alone doesn't drastically affect sound levels. The actual noise you're hearing from the top end of an airhead engine is mostly from the valve train itself — rocker arms, pushrods, and tappets — not so much from the shape of the cover.
Later square covers tend to seal a bit better and are a bit thicker in places, which might dampen a small amount of high-frequency mechanical noise. But in practice, it's subtle.
Valve adjustment and rocker arm end play have a far bigger impact on noise than the type of cover.
Many airhead folks even swap between the two styles purely for aesthetics, with no noticeable difference in sound.
If you're hearing noticeable valve clatter, it's usually worth checking:
Valve clearances (they should be spot on when cold)
Rocker arm end play
Pushrod tube seals (loose seals can resonate a little too)
So — while the square covers might offer a slight acoustic benefit because of better sealing and potentially thicker castings, it’s not a dramatic difference. Most of the "quieter" reputation comes from other improvements in those later motors.

Are you thinking about swapping them on your bike or just curious about the design change?

[JohnT]

No didn't check rocker arm end float, never gave it a thought. Will check.
Have the anti ringing inserts, interestingly MaxBMW consider them unnecessary?

[Rob Frankham]

Have the anti ringing inserts, interestingly MaxBMW consider them unnecessary?

They certainly aren't necessary but many owners find them desirable...

Rob

[dwerbil]

No didn't check rocker arm end float, never gave it a thought. Will check.
Have the anti ringing inserts, interestingly MaxBMW consider them unnecessary?

I never knew of the pillow-blocks and of 'pinching' them together when torquing the heads until I came across this forum back in the late '90s. When torqued, like in the image with big channel locks or c-clap, it does quieten the chatter down.

[SteveD]

https://youtu.be/8H7PV2_CN-o?si=HTQ0UHptXjJcjV5t

At 38minutes in...monolever valve adjustment, shim clearance check etc.

[Rob Frankham]

No didn't check rocker arm end float, never gave it a thought. Will check.
Have the anti ringing inserts, interestingly MaxBMW consider them unnecessary?

I never knew of the pillow-blocks and of 'pinching' them together when torquing the heads until I came across this forum back in the late '90s. When torqued, like in the image with big channel locks or c-clap, it does quieten the chatter down.

You just have to bear in mind that there are 4 different types of rocker assembly. The original type has plain bearings, the first mod has needle rollers with the pillow blocks not positively located in the head and the later two have the blocks actually let into the head. The procedure with clamps (or even the BMW special tool), only applies to the first two types but, after 1980, it will make very little difference (I've tried ). On a monolever in particular, the way ahead is to use shims to take up any slack and also replace the nylon top hat washers if they are very worn.

Just to make things difficult, in typical BMW fashion, early engines can be (and often were) upgraded to a later rocker assembly so it's quite important to make sure what variant you have... In the context of this post, however, since we're talking about a monolever anyway, it's almost certain it'll have the final version and compressing the pillar blocks won't do much.

Rob

[JohnT]

Set too today to check rocker arm end clearance. 3 within limits one 0,25mm or in figures I understand 0.010 inches. No wonder I had a noisy top end. Have ordered some shims and a plastic bush.
Will removing 2 of the 6 cylinder head nuts compromise the head gasket seal?
Out of interest and to satisfy my curiosity I have acquired two square rocker covers to carry out a noise comparison.