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Old 03-27-2014, 04:25 PM   #1
backfill OP
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Location: Ancaster, Ontario
Oddometer: 59
mixing rocker arm assemblies

I am rebuilding a 1975 R75/6 that had the crap beat out of it with a hammer. I have acquired a later set of nikasil lined R80 cylinders and heads to put on the /6. They were machined so they fit perfectly. The valves and springs were replaced and I installed new rings and push rod tube seals. It should be as good as new!

When I assembled the engine today, one of the newer rocker arm assemblies didn't fit. I am not sure why, but the holes wouldn't line up properly and it wouldn't fit over the studs. I think it is missing some spacers. I will check around tomorrow and see if I can find any.

Being crafty I used one of the rocker arm assemblies that came off of the old head. They look slightly different but they I believe they are at the same level.

I couldn't see any issues that might be caused by doing this, but thought I should check with the collective. Will there be any issues caused by using two different rocker arm assemblies? If I find spacers, I will use the newer assembly so there won't be any question of an issue.

My, that was a long posting for a short question.

thanks in advance
Phil
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Old 03-27-2014, 05:04 PM   #2
disston
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Location: Silver Spring, Md
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The place to learn about Airhead rocker arms is on Anton Largiader's site. He is also a member here;
http://www.largiader.com/tech/rockers/
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Old 03-28-2014, 10:08 AM   #3
backfill OP
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Charlie, thanks for the link. I hadn't found that information on rocker arms before. Very informative.

I measured the width of my rocker arms today. Three are 55.8 mm wide and work perfectly with the end blocks. This seems reasonable with the 1976 to 1984 rocker arm assembly. The forth is 57.6 mm wide, so I think it belongs with a /6 rocker assembly. It seems that the parts have just gotten mixed up. I will sort this out with the guy I bought them from.

Some of the rocker arms are missing needle bearings. Sigh. Something else to find and fix.

cheers,
Phil



Quote:
Originally Posted by disston View Post
The place to learn about Airhead rocker arms is on Anton Largiader's site. He is also a member here;
http://www.largiader.com/tech/rockers/
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Old 03-28-2014, 11:28 AM   #4
disston
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You have to be careful when handling these rockers that have the needle bearings in them. Keep the shafts in the rockers and if they get taken out for any reason be gentle with the rockers because the needles will fall out. Some grease or assembly lube can be used to help keep them in place but they can still get lost.

Eventually the needle bearing may get worn and they break the ends off the shells that are keeping the needles in place when the shafts are installed. The needles will work their way out of the rockers even in use and you can find the needles in the valve covers or even the oil pan. They may start making noise if they get this bad. I have heard riders say they were missing a few needles and still used them. I wouldn't do that. If the ends of the races are cracked or broken the bearings should be replaced. These bearings are not a common bearing store bearing. They are proprietary and usually only available from the dealer or the normal parts sources. They are not a cheap bearing. Max BMW currently lists them for $27.47 ea. And there are two of them per valve or eight in a single motorcycle.

When putting the whole thing together squeeze the blocks together so there is zero up and down free play while still not binding. The rockers should move freely thru the entire range of movement they use. Any excessive free play in the vertical axis can cause the rockers to slam into the blocks and break the shells of the bearings.

Charlie
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