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Question - swing arm out, what should I do?

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Kidasters
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Question - swing arm out, what should I do?

Post by Kidasters »

Hey guys -

I've been working on my R100/7 lately. A few years ago, I broke one of the ears on the transmission cover when the circlip fell out of the pin on the throwout arm, and when the pin slipped - snap.

Anyway - this weekend, I finished removing the rear 1/2 of the bike in order to get the transmission off. The R100 shop manual claims you can do this without removing the swing arm, but I don't know how.

So - I have the entire swing arm off. I'm a little worried, the grease around the bearings looks very dry/funky, so I'll do my best to clean that out and pack some new grease in there. I figure I'll also clean everything up back around the break shoes, and when mount it back on the bike, I'll drain and re-fill the fluids. I'll also re-grease the splines on the rear drive before putting the rear wheel back on.

Is there anything else I should be doing while I have it off the bike? Do I need to pull and replace the bearings?
What do you mean "next" project?

--My wife

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srankin
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Re: Question - swing arm out, what should I do?

Post by srankin »

I don't have the parts here but you say the grease in the swing arm bearings looks dry? I would take the time to pull the bearings out clean inspect and repack them at least.
As they don't spin, the wear on them is more from hammering so they tend to stick or hang up when worn. The good news is they don't wear out as fast as a wheel bearing. Feeling the race, check for indents, check to see they do spin free, even though they don't in the swing arm. Really, unless you have a log of miles and hard use on the bike, you may be able to reuse them.

As far as the drive shaft, there is nothing to really do. Clean the brake shoes, and lubricate the final drive splines be sure not to use regular bearing grease on them.

You may want to order a new swing arm to transmission boot and clamps, at least check the condition of them. Remember when you put the boot back on, there is a top and front or transmission side on it. Sorry, I am not in my garage so I can't remember what the German words on the boot are for top and Transmission, to tell you the orientation. Check out Brook's airhead garage videos, I am pretty sure he will have a good video on all of this.

Don't forget to lube the transmission input shaft with the proper lube.

Good luck, St.
Owner of a 84, R80RT and 78, R100RS

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Kidasters
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Re: Question - swing arm out, what should I do?

Post by Kidasters »

Yep - good thoughts. I think the last time I did final drive splines, I used a lithium grease. I'll have to see what I did there.

OK - sounds like I'm on the right path anyway. Thanks for the reply.
What do you mean "next" project?

--My wife

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srankin
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Re: Question - swing arm out, what should I do?

Post by srankin »

Ah, no, check with Brook's garage and find what he uses for spline lube and final drive spline lube. Lithium grease in the wrong formulation will just melt or spread to things you don't want it to spread too, like for example on the transmission input shaft, it will spin off onto the clutch. On the final drive splines it will spin off into the drum brakes.

Now, I use never seize for my final drive splines, not quite what BMW says to use, frankly, I have only worn out three sets of splines in the past 37 years and now 224000, miles. The last set of splines replaced at 220K miles were done because the rear wheel drum had worn down along with the shoes and needed changing. New wheel, new splines.

For the transmission input shaft, I use what I call bubble gum grease. My old airhead shop used it and back 32 years ago I bought a tube and it has lasted all that time on the shelf. I don't use a lot at a time. Anyway, the lettering on the tube itself has long since gone away so I can't tell you what company made it or particulars about it. It was for heavy equipment.

Brook and others will have the information on their websites and the parts suppliers almost all have something that will work for you.

lithium grease is fine for the swing arm bearings. St.
Owner of a 84, R80RT and 78, R100RS

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schrader7032
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Re: Question - swing arm out, what should I do?

Post by schrader7032 »

For the input shaft, which sees sliding action from the clutch disk, the grease to use should have some tackiness to it as well as some moly. Regular wheel bearing grease contains moly. I have a tube of Chevron NLGI2 red grease which is tacky. I mix 2/3 of that with 1/3 moly wheel bearing grease.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Kidasters
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Re: Question - swing arm out, what should I do?

Post by Kidasters »

I will find an appropriate lubricant for both. Thanks guys.
What do you mean "next" project?

--My wife

chrishea
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Re: Question - swing arm out, what should I do?

Post by chrishea »

For the swingarm bearings, you didn’t specify what year R100/7, however, we probably can assume the bearings are at least over 40 years old. The bearings should be the plain 30203 bearing (BMW changed to a different bearing more expen$ive bearing mid 1981). The seals are unique. You will destroy the seals when attempting to pull the bearings out. If you change the bearing, pulling the race out requires a special “blind” bearing puller.

For the clutch splines, a good sticky moly grease is best. There has been lots of discussion on the interwebs over what’s best. For the rear wheel splines, similar. Just don’t put too much on or it makes a mess.
Chris
Seattle

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Kidasters
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Re: Question - swing arm out, what should I do?

Post by Kidasters »

It's a 78 R100/7. Thank you for letting me know.
What do you mean "next" project?

--My wife

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srankin
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Re: Question - swing arm out, what should I do?

Post by srankin »

Looking at Max's microfiche, I am lead to believe you shouldn't have a problem replacing seals only if the bearings are good just dry and in need of repacking.

The tool needed when replacing the bearings is not needed to pull the bearings but is needed to remove the bearing races. As mentioned, it is a blind bearing removal tool. I would not worry about removing the races unless you really need to replace the bearings. Again, the bearings are subject to hammering action more so than spinning. Minute indents in the races and sticky bearings need replaced. If they spin freely and there are no signs of indents or hammering wear, just repack and reuse. They really don't wear out for a long time unless they were dry. Good luck, St.
Owner of a 84, R80RT and 78, R100RS

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Flx48
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Re: Question - swing arm out, what should I do?

Post by Flx48 »

If memory serves, swingarm bearings have been the same from the first Earles fork models on through /5/6/7.
While many other cycle brands were using bushes in the same application, BMW had expectations of sidecar use with the Earles models and the need for a robust lateral swingarm connections, hence the roller bearings, and apparently, they passed the 'if it ain't broke don't fix it' test for the subsequent models .
Unlike bushes, with proper adjustment, seal protection, and lube they could last forever.

But lube can be the issue; these swingarms probably arc less than 25 degrees in use, which means the rollers probably rotate less than half their circumference.
This has the effect of squeezing out all the lube between race and roller, without replacing it, and so running dry.
In a wheel bearing application, turning probably 500 revolutions per mile, the bearing is constantly regreasing itself, race and roller.
In a swingarm application, the roller bearing can have the opportunity to run dry for long periods of time.

I think the Earles era manual suggested swingarm adjustment every 3 oil changes, and repacking every 6 six changes, which equates to repacking every 6 thousand miles or so, right along with their wheel bearing repacking schedule, so BMW understood the implications.

I don't know what the /5-/7 manuals recommend, I'd expect with improvements in grease formulas from /2 days, techniques for adding grease externally, and owners wanting less frequent maintenance, the intervals are probably greatly increased.

One can pop the seals out, (they're cheap to replace) remove and clean the inner race/rollers, and clean and inspect outer race.
If there are divots in the surface of races or rollers, (metal deterioration- signs of contamination/poor quality) or dents/ flat spots (loose adjustment- brinelling) or discoloration/ghosting (alternating shiny and dull surfaces- false brinelling) the bearing could be replaced.
Swingarm bearings do not do the same job as wheel bearings, the stakes are lower; for me the bar is set at what I can feel with my fingernail.

On another topic, as Chris mentioned, things are now 40 years old; you may also want to take the opportunity to inspect the rear end for signs of oil seepage in all three directions.
With the rear already out of the bike, you've probably halved the cost of resealing the rear to 1-2 hours shop time.

Best-
George

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