Tuesday, November 30, 2010

Working on Airheads

On Saturday evening, I went to visit out local Air Marshall, the organizer of our BMW Airheads chapter. He had some maintenance to do on his bike and I was more than willing to help especially since it is the same year and model as my bike. It's even the same color though less than half the mileage. Pulled both wheels to check the wheel bearings and to take a look at the rear splines. The splines are another common wear point on these old machines as they usually don't get greased often enough and if they do, it is usually with the wrong type of grease. His looked like they were in great shape. The tires had quite a few miles on them and included a round trip to the BMWMOA rally in Redmond last summer. The pavement material used on the Alaska Highway is very rough and I hear it is pretty hard on tires. New tires on order. On Sunday afternoon, another small group of Airheads met to adjust the headset bearings on an R100GS-PD. I think the main reason for getting together is to just talk and have a beverage. George Rahn, the local Airhead guru, also showed up later to take a look at the adjustment. He talked about some of the differences between the newer GS and the older models that most of us owned and brought a special BMW tool for doing the same task in a more "production" manner using a torque wrench instead of just by feel. Unfortunately, the took was for another model. I also learned that there was an old factory bulletin out regarding transmission oil changes for the R100 models. They changed not only the type of oil but also the amount. They recommend overfilling the transmission by 50cc by tipping the bike to the side. My Clymer manual makes no mention of anything like that.

All of this activity motivated me to finally remove the heads from my R100RT. The first step is separating the carbs from the head. Since I don't intend to work on them, I'm choosing to simply leave them attached to the bike. The carbs are simply supported by their plumbing and it is a simple task to loosen the rubber sleeves. The carb is now hanging from the fuel line and the choke and throttle cables.

The more challenging task was removing the exhaust system from the exhaust port. This involved removing the mufflers, crossover, Brown side stand and these large aluminum finned nuts threaded into the exhaust port. A special tool is needed for the large nut but fortunately, they are readily available on the aftermarket. It's recommended to remove the exhaust nuts yearly to keep them from seizing up. (aluminum on aluminum). Plenty of high temperature anti-seize simplifies this task.

The valve covers and spark plugs are removed followed by the six head bolts. Four of these are holding on the rocker arms. The pushrods are pulled out then the head is simply pulled off of the studs. The cylinders look to be in good condition so there is no reason to continue removing parts. The cylinder will be covered by a large plastic bag to keep dust and dirt from entering the engine.

This is the left head and the exhaust valve is on the left. If you compare the intake and exhaust valves, you can see that the edge of the intake is sitting above the valve seat. The upper edge of the exhaust valve is actually below the top of the valve seat, enough so that you can actually see a thin sliver of the valve seat. This is the side that I noticed the very thin edges of the exhaust valve last spring which indicated that I have a problem.

For comparison, this is the right cylinder head and the exhaust valve is on the right. You can see the edges of both of the valves. This side looks fine but I will have both heads done at the same time. Now I just need to contact the shop. From the color of the deposits on the valves, it looks like the left side may be running a little leaner than the right...

All of the parts have been bagged and labeled to simplify reassembly.

This morning, it was -33°F. The weather is trying to make up for the unseasonably warm temperatures of last week.


  1. nice writeup and pics....you'd be amazed how similar the beemer airhead engine heads are to the ural cyclinder heads....one would almost think the Russians "liberated" the factory from the Germans after WWII.

    heck, if you're willing to do what you did to your beemer, a Ural would be the same.....I'm debating taking the tranny from the engine to lube the spline.


    Redleg's Rides

    Colorado Motorcycle Travel Examiner

  2. RichardM:

    I'm learning a lot and hope that I will never have to use this information, but you have written it up in such a manner even I can understand the problem. The pictures help a lot

    Wet Coast Scootin

  3. Hi Richard!

    Great write up! Thanks for the info and visuals. Looks completely different than mine with the push rods on yours for the cam on mine.

    But I am sorely confused on the pictures of the left and right. To me, the top/left one looks cleaner. The bottom/right one seems to be attracting crap. So it should look more like the bottom/right one??

    In all, I am learning lots. Thanks for taking the time to document it. I never knew those were actually finned nuts! They are so cool!!


  4. I saw your post that it's 75 degrees colder there. I feel much better now! :)

    -33 OH MY!

  5. Thank you all for the kind comments.

    Pulling the tranny to lube the splines should be pretty straight forward if it is like the Beemer. I didn't completely remove the transmission but just pulled it back just enough to get to the splines.

    Just avoid the early 80's BMWs unless they already had their heads gone through. I didn't know about this before I bought mine. Didn't do enough searching on the Internet...

    Maybe I should have said the right head was running a lot richer due to the color of the valves. The mixture in the left one (leaner and cleaner) is probably closer to correct but the higher temperatures contribute to the valve problems in the early 80's airheads. Since the right one was running richer and cooler, there wasn't much evidence of the problem.

    In that case you'll like today even better. It ht -40F last night in some parts of town (North Pole).

  6. I've worked with airheads but they didn't have two wheels. On the other hand, there was nothing wrong with them that a good wrench to the head couldn't cure!

  7. Nice write-up and photos Richard! I admire your ability to forge ahead on this project considering the season. I hope the inside of your garage isn't -33.

    About ten years ago I replaced the head gasket on our Toyota truck with snow on the ground but I had to finish it for transportation.

    You are inspiring!

  8. The weird part is that it seems that living in such cold temperatures is entirely normal. How do you get a newspaper out of the driveway in minus 40? Does the car start or do you have one of those electric plugs? Does the power go out? I can't imagine day to day living in a place with four hours of sunshine/daylight.
    It gets cold in the Keys by virtue of the fact it's thirty degrees cooler than normal, but even for you minus 40 can't be anything like normal.
    Cylinder heads? Everyone does that. Living in minus 40? Brrr.

  9. Conchscooter:
    Once the temperature drops below about minus 30F, it really doesn't matter anymore. Life goes on. I can't remember school ever getting cancelled for cold. I think the schoolbusses stopped running when it hit minus 65F once or twice. People are still out walking, jogging, bicycling and skiing down to about minus 30. There are even a handful of sidecar rigs out and about. There is very little humidity and rarely is there any wind so actually it sounds a lot colder than it feels.

    Several times per week, I try and get in a 5 mile walk outdoors. You get pretty used to the temperature. We start to have real problems if it warms up in the middle of the winter. Before Thansgiving, we had an inch of rain. That layer of ice is still on the road.