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.