I am requesting diagnostic consideration for one head getting hotter than the other. I am thinking everything from air leak to valve adjustment (exhaust valve problem) to bad rings. This is my first beemer. 1981 R100 RT. I have had it only a few weeks and have been combing through it before I put it on the road. My valve cover gaskets come in this week so I haven't cracked it open yet. My experience is with old air cooled Honda's. The plug actually looks good to me. Any common issues? I have watched about every video from Chris Harris on the topic. I am curious what you guys think. I looked through the forums and hadn't found much on the topic. Any links would be appreciated.
What I have done so far includes complete fluid change, carb happification (not a complete carb rebuild but cleaned up and new bowl gaskets), new fuel lines, clean gas.
That is great information. Thanks for taking the time to reply in such detail.
To answer your first question, the right head is hotter to the touch than the left when warming up in the shop. I haven't taken it out on the road due to this. I don't want to cause any unnecessary damage. I always feel the heads as they warm up on my bikes. Like I mentioned, my experience is with air cooled Honda's. I always let them get hot before riding. So, I did the same with the Beemer. It gets pretty darn hot compared to the left. I checked all the rubber and snugged up the hose clamps. They are showing a little dry rot and new ones are in the mail. With my Honda's I would just spray them with a little wd-40 to check for leaks but I don't want to do that with this bike. I am just planning on replacing them. Fluids: I found a little granular metal on the final drive plug (very small salt grains, very few). The transmission plug was stopped up and required a poke before oozing out some pathetic snot initially then good flow (no shavings or other metal found). Drive shaft was unremarkable (seemed normal). My experience with carb kits has been mixed with regards to Honda. I prefer saving and reusing what I can (needle valves, jets, screws). New stuff is garbage. Don't want to waste money on junk. Not sure how BMW parts compare. When you mentioned the head pipes were you suggesting an air leak there? I am guessing these use crush rings like my other bikes and that those may need to be replaced. Am I on the right track there? As far as exhaust nut wrench, do you recommend BMW wrench or is an after market wrench fine? Hope I am not abusing your generosity. Let me know. Thanks again
Forgot to mention that the engine oil was unremarkable (seemed normal). Thanks again
I'm not finding many Airheads in Western Texas. Closest gathering is in San Marcos TX which is about 4 hours away. Thanks for your input and I will look around the forum for appropriate places to ask my questions. I am sure I will have plenty. Thanks again and for what it's worth I received my calendar and it was almost in two pieces. A little tape and it's like new. Kind of cracked me up. Looked like the mail man fought off an angry cat with it. Ha.
Not a big deal. Thanks again
As others have heard me preach, the new fuels are very bad to coat the inside of the carbs. The main problem, if the carb isn't completely gummed up, is that the thin coating on the carb "needle" will lean out the mixture in mid-range where most of your riding will be done. If you have the slides out, you may wish to do 2 things... 1) clean the needle with carb cleaner and 600 grit emery cloth, and 2) use a caliper to insure that both needles are protruding the same amount for the slide. The way Bing designed these is not like a typical Jap or Brit carb... You can't directly see or check the needle slot position. So you have to measure. The slots are ~1.5mm (0.060") apart, so you are either way off or right on.
Secondly, hand measurement of temp is so inaccurate I'm going to tell you not to worry. Go ride the bike (with a carb cleaner additive in the fuel, like StarTron) and don't worry about it unless the plugs or pipe exteriors are vastly different colors.
You need to get this bike out on the open road ASAP. Start with 15 minutes rides and work up until the trust level improves. Simply running new fuel through the engine is going to change all the carb and valve settings, so the emphasis MUST be on running, not in-shop testing and fiddling.
Hope this helps.
PS. As a pro bike mechanic, I can tell you the best tool you can take with you on these first rides is a cell phone !!
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
A few thoughts to share. It's not good to let an Airhead, or any aircooled motor, to come to full operating temperature by idling at rest. Scott's recommendation about taking a spirited ride is best.
One cylinder hotter than the other suggests a lean air/fuel mixture on the hotter cylinder. If you put in new spark plugs, they should be changing color from running. This is a good way to observe what your air/fuel might be running at. Black and sooty is too rich. Whitish and ashen is too lean. Golden brown like the color of pancakes is just right.
former Airmarshal, IL.
Let me add another vote for riding versus letting the bike run in the shop. After a good 15 minute ride you can come back and sync the carbs (with the aid of a window fan blowing on your motor), then adjust the valves when it cools.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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