Cylinder head quietening modifications

**John Roberts** · #1 14 Mar 2005

Hi,

I believe there are 'hush' kits available for airheads to make them quieter, my own interest is in those for airheads of around 1982. The Motor Works catalogue lists rubbers to cut down resonance in the cooling fins, but I believe there are some other modifications to the rocker gear to further reduce the noise.

Thanks,

John

**Grant Johnson** · #2 14 Mar 2005

The rubbers help a lot.

The only other change was to the rocker arm bearings and shims, a year or three after yours I believe. Quieter, yes, but only very slightly, not sure it's worth it. DO listen to a later one with correctly set rocker end float before splashing out.

For that matter be sure your end float is correctly set too! Much discussion on this on the HUBB.

**John Roberts** · #3 14 Mar 2005

Hi Grant

I've had a search as you said but didn't find much of help this time. The end float on my year ('82 R100RS) is fixed, the rocker shaft brackets are mounted on conical seatings and so cannot be pushed sideways to adjust the float as was possible on the earlier engines. So, if you say that the main benefit comes from the fin rubbers, then I'll just go for those instead.

Many thanks

John

**Grant Johnson** · #4 14 Mar 2005

See http://www.horizonsunlimited.com/ubb...ML/000483.html

**Grant Johnson** · #5 14 Mar 2005

also http://www.horizonsunlimited.com/ubb...ML/000291.html

**Frank Warner** · #6 15 Mar 2005

Don't think you can buy the old rocker gear now. What you will get is the newer rocker gear - with the plastic bit on the end.

Certainly the rubber dampers are the cheaper and easier bit of the quietening operation. But I don't think that it will help any if the rocker clearance is out. Do the rocker clearance first and see if that is quite enough before you spend your money. Then do the rubber dampeners.

**John Roberts** · #7 17 Mar 2005

Hi

I just checked the end float on one head with a dial gauge and found the inlet rocker to have 0.5 thou (0.01mm) and the exhaust to have 0.8thou (say 0.02mm); not a lot really.

The thread you refer to on
http://www.horizonsunlimited.com/ubb...ML/000483.html
is certainly interesting but I don't think it refers to my particular year as mine has the conical seatings for the pillow blocks and so are not adjustable by varying their relative spacing, and shims that thin aren't available. Nah, I'm happy with my end floats as they are, I think. Incidentally the finish on the rocker shafts was still absolutely perfect, dead chuffed.

Actually, by now I've reset the exhaust valve clearance to 0.008 ins as suggested by Haynes as opposed to the 0.006 as stated in the BMW manual, with unleaded doing its worst on the valve seats then I think it's wiser to err on the high side. Pity it makes more noise, though!

Cheers,

John

**John Roberts** · #8 13 Apr 2005

PS it makes a hell of a lot more noise with the suggested 0.008ins clearance than with the original 0.006. I think I'll go back to 0.006, and keep a close eye on it.

J

------------------
Johnefyn

**dc lindberg** · #9 25 Sep 2008

What did you opt to do ?
How did it work ?

I got the new rockers since mine were too worn. Contrary to all claims - I found the new (plastic spacer) to be more noicy than the old (1984)!
Installed valve end caps from VW - that did have an enormous effect on the valve noice. It builds 2mm, but that does not seem to have any effect.