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Topic-icon '81 R100RS: Bars keep rotating up/down

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1 month 1 day ago #6490 by Wobbly
Sold my '79 and moved on to a '81 model. This bike has the real RS bars, but the bars don't have any type of knurling at the clamp locations. Thus, when I'm man-handling the bike on/off the center stand, they often rotate up/down. It's also started to do a little of this on the road... which can be very "unnerving" in a corner. I have tightened down the 4 clamp bolts so tight that I'm afraid of breaking the aluminum top clamps.

Is there a secret to keeping these bars from rotating in the clamps ??

Don't hide 'em, Ride 'em !!
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1 month 1 day ago #6491 by 8166
Replied by 8166 on topic '81 R100RS: Bars keep rotating up/down
I can think of a few ways to stop the unwanted rotation.

Easiest for me would be to get some powdered rosin (mine came from Brownell's), mix it with some carb or contact cleaner to make a paste, and paint the inside of the clamps and the part of the bar that is held with rosin. It's pretty sticky and might just be all you need.

If that doesn't work, you could make up some shims from aluminum beer cans and put those in there.

If you're still having problems, you could use a center punch to raise burs on the inside of the clamps and/or the outside of the bars under the clamps.

Then there's always good ol' friction tape, maybe a turn around the bars where they go into the clamps.

Could be that someone in the bike's past used 7/8" handlebars and that spread the clamps out. I believe BMW bars of that era were 22 mm in diameter, or 0.009" smaller than the 7/8" standard.

Hope that helps...

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.
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1 month 1 day ago #6493 by Wobbly
Replied by Wobbly on topic '81 R100RS: Bars keep rotating up/down
Important point there, about the 22mm bars. Much obliged.

Think I'll try adding some surface roughness to the bars via center punching. That's a great idea.

Thanks.

Don't hide 'em, Ride 'em !!
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1 month 1 day ago #6494 by 8053
Replied by 8053 on topic '81 R100RS: Bars keep rotating up/down
Beer can ribbon shims would be good, cheap fun.
I like Scott's idea of using a punch to raise burrs in the contact zone.

James Strickland, IL. Airmarshal
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1 month 7 hours ago #6501 by Wobbly
Replied by Wobbly on topic '81 R100RS: Bars keep rotating up/down
OK, so I removed the bar caps one at a time and added center punch dimples to the top side of the bar. That fixed it !

Great suggestion. Thanks again.

Don't hide 'em, Ride 'em !!
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