New Airhead (winter fixin up questions, etc)

I missed my old R65, and after the 2019 Rally, been on the hunt for an inexpensive one to tinker with and maybe completely re-do (another thread will ask for photos). Anyhow this one ended up being in much better shape than I thought finishwise, but still needs a going over mechanically. So, oh Airhead fans, please throw your advice into the ring.

1981 R100 with 34,000 (today) miles. Title from 2009 says 33,695 miles. Odo works so I'm guessing it wasn't loved that much.

Here's what I know needs doing

• Adjust sidestand
• neutral switch
• new tires (these can vote. I'm not kidding)
• clutch adjustment
• overall tune up
• forks oil?
• all fluids flush

First, some photos.

I took off the backrest and the softside bags to start and gave it a good wash. The owner left his other helmet in one bag. Kinda mildewy and gross. In the trash!

I think this is a BMW sidestand. It has a lot of slop in it, I was thinking of shimming it with a washer or two. Does that make sense?

So onto the other things.

The PO said he bought it unassembled from his brother in law who painted the tank and fender. He said it needed a new neutral switch. I was going to test the switch per some post I found online. Turns out, there doesn't appear to be any wiring going to the switch! I'll have to do a little tracing to see where the wires might be.

The clutch lever pulls way in before engaging. I'd like to adjust it more like my R1150 where it's just a little pull. I know it won't feel exactly alike, and I know it can be adjusted but how's it "supposed" to be?

Bike starts and idles OK, but doesn't exactly take off like I'd expect a liter bike to do. That said it's probably way out of adjustment. When up around 3000 rpm, it stumbles like my old R65 and just falls on it's face. Much backfiring, which was fun, but only for annoying the neighbors. What order do I do it all in? Valves, plugs, timing, carbs?

The forks seem way soft. Like a dirt bike. New oil? Thicker oil? What?


See my first post about how many miles it was ridden. I looked for the date code on the tires.... 2001! (Which ironically is on Turner Classic Movies tonight).

Nice starting point, it looks complete and unmolested. Are the pushrod tubes leaking, or the RMS? They usually are on old airheads. All very doable by the home wrench. Nice project.

How are the fork gaiters? Hard to tell, but it looks like they might be split in some places.

As for the side stand, I suppose you could shim it, but what's happened is the connection on the stand side has gotten wider and thus it's sloppy. Probably, too much weight has been put on the bike when on the side stand, resulting in the spreading of the stand.

I believe this should be the way to adjust the clutch:

http://www.rubberchickenracinggarag...d Clutch Cable Replacement and Adjustment.pdf

chunk said:

Nice starting point, it looks complete and unmolested. Are the pushrod tubes leaking, or the RMS? They usually are on old airheads. All very doable by the home wrench. Nice project.

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Yes, pretty complete. Better starting point than my R65, which was a lot rougher shape. Yes, the pushrod seals are leaking (left some on the U-haul trailer). I don't think the RMS is (yet).

@20774, thanks for the link! Fork gaiters looked OK to me. Would the side stand be a goner then? I could keep an eye for a Browns. I see why people complain about these.

I might need to lube the center stand or something, it's not as easy to get onto (or off) as my newer bike.

Good starting point

You look like you have a very good starting point. The bike looks pretty good from what I can see.

In regard to the neutral switch wiring the leads to the switch are a sub harness of the main harness. They plug in just about at the frame back bone. EME has them for sale if you need one.

So, you have question marks after your check list. I would say yes to everything. Start at the forks, pull them apart and not only drain them but if you feel up to it, flush them out then refill. Since the bike has gaiters on it, unless you see rust, you may not have to change the fork seals. New fluid will make a big change. Check the steering head bearings to see they turn freely and are not too tight. If it is the still the factory grease in them, there may be a problem. BMW about that year used some grease which had the habit of solidifying. I don't remember how bad a problem it was but I know I had it and one of my friends had it happen to them.

The push rod seals are a bit more complex to change in that the valve system must be disassembled in order to change them. One good thing might be in your favor is the clips on the piston wrist pins may be snap ring style instead of the older spring style. With the snap ring style and the use of proper snap ring pliers, there is far less chance of having one spring off into the dark recesses of your garage if you have to remove one. Sorry it has been a bit of time and I don't remember if you can just shift the jugs out enough to replace the push rod seals or, the wrist pings have to be taken out of the pistons and the jugs further slid outward.

Pay careful attention when draining the transmission, driveshaft and final drive oil to look for signs of water. The plug in the transmission is magnetic so if there are big chunks of metal on it, you may have a problem.

Kurt posted the clutch adjustment instructions.

As for the carbs and all the problems. They may need at the least, cleaned out. If the bike sat for a long time with gas in them, they could be badly gummed up. The stumbling may also be due to a bad diaphragm.

You have electronic ignition on the bike so there is no points to mess with. I would do a quick check of timing but in most cases with the electronic system if it was set correctly, it never changes until the timing chain goes and if your mileage is correct you won't need a timing chain yet.

Oh yes, flush the brake system. The handlebar mounted master cylinders are more prone to degraded fluid due to more exposure to the sun as well as water. I can't be certain from your pictures but I am assuming you have a rear drum brake as the disc was only on the RS and RT models I think?

Last thing, looks like at one time someone installed a deeper oil pan on the bike. If you decide to get rid of the stock center stand and want to install a (getting rare to find) Reynolds ride off stand, the Reynolds stand's cross bar might not clear the oil pain. I can't say anything about "newer" bikes being easier to get on the center stand because I have never owned one newer than my 84, LOL. I does make sense BMW would redesign over the years and newer models to make it easier.

Have fun, St.

Thanks for the advice!

I've got to drain some of the gas to lift the tank and check for the wiring. It didn't appear to be hacked up at the back of the gauges.

I don't trust this side stand. Too much lean. I took it off to see if I could shim it. I could not.

I did pushrod seal before. It was the whole jugs off deal. Not scary. I was just never good at carbs. BUT now there's youtube and lots of resources I can follow.


This will hopefully help me manage the insanity of being at home and not being able to leave . At least I can go to the garage to monkey with it.

Some years/models had a bushing in the sidestand mount that is easily replaceable; smear some moly grease on the inside and outside prior to installation.
You can also squeeze the ears back closer together in a vise.
When you install the screw that holds it all together (and if it looks worn or is a sloppy fit in the bushing, replace it), make sure there's no grease on its threads - it will probably pick some up as you push it through the bushing - and crank that screw down tight.

Note: the above image on the right seems to be the appropriate one for the '81 R100.

videos and pictures

Check out Brook Reams's website https://brook.reams.me

He has some amazing videos and pictures.

Everything on an airhead is pretty simple if you have the skills, resources and patience to work on them. I am go for two of the list, LOL. St.

STEVENRANKIN said:

So, you have question marks after your check list. I would say yes to everything. Start at the forks, pull them apart and not only drain them but if you feel up to it, flush them out then refill. Since the bike has gaiters on it, unless you see rust, you may not have to change the fork seals. New fluid will make a big change. .

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What is the difference between draining and refilling and "flushing". I thought that was technically the same thing, but maybe I'm getting mixed up in terminology.

should be

Ah, it should be drain, as in drain the existing fluid, Flush should be second, sorry, as in flush out any crud in the system from old fluid break down. Finally refill with the proper amount of fresh fluid.

Flushing may not be needed if the old fluid looks fairly clean. St.

Will be keeping up with your progress. I’m in a slow process to freshen up a red ‘82 R100 standard, too. I’ve removed the carbs and taken them to my buddy Leo Goff for a rebuild. The bike will get a lot of the other components upgraded after the engine tuneup. Pictures of the bike on my moa thread Ride, eat and meet in the south region. Page 185 picture#2770-2772.

barryg said:

Will be keeping up with your progress. I’m in a slow process to freshen up a red ‘82 R100 standard, too. I’ve removed the carbs and taken them to my buddy Leo Goff for a rebuild. The bike will get a lot of the other components upgraded after the engine tuneup. Pictures of the bike on my moa thread Ride, eat and meet in the south region. Page 185 picture#2770-2772.

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Nice bike. I see yours is red on the rear fender. I'm not sure why the PO(s) went down the path they did with this one. I don't even know if its a BMW color. Anyone?

Tire size?

I looked at the tires and the front has a size I don't understand: 3.50 - 19 - 57. I can find tires in that size, but is this some imperial measure? The rear is a 120/90-18 which follows the convention I'm familiar with.

Those don't seem like proper tires for an '81 R100. Front is 3.25x19 and rear is 4.00x18. Personally, I'd stay with inch-sized tires rather than go with metric tires.

20774 said:

Those don't seem like proper tires for an '81 R100. Front is 3.25x19 and rear is 4.00x18. Personally, I'd stay with inch-sized tires rather than go with metric tires.

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Hmm. I've never heard of inch size tires. On anything, really. I'm not wed to this of course and won't put them on myself, just was doing some pricing. Odd to have inch sized anything on a clearly metric bike.

R65_Steve said:

I looked at the tires and the front has a size I don't understand: 3.50 - 19 - 57. I can find tires in that size, but is this some imperial measure? The rear is a 120/90-18 which follows the convention I'm familiar with.

Click to expand...

The "57" is the tire load rating. There should also be a speed rating next to it.
Here's an example for an Avon front that will fit properly.

Tire Size:3.25-19
Model:AM26 ROADRIDER
Tire Width:3.25
Rim Size:19
Load Rating:54 (max 467 Lbs.)
Speed Rating:V (max 149 mph)

My ‘82 is not stock, previous owners did their mods, just like previous did mods to yours. Easy to change to what U like best. Get her tuned up for a proper safe ride, then get down to doing or not doing to what U think is best for your ride. Ride and enjoy.: