TECH
InherentVice Your tech questions answered By Peter Boggia
In writing this issue’s column we kept coming up with very similar responses to every question. Mostly, the answers were comprised of more questions. Often the same questions treading over the same ground—all tied to establishing some basic parameters before climbing out on any diagnostic limbs. This reveals a critical limitation with the very idea of a write-in tech column, which inherently doesn’t allow for the back-and- forth dialogue so criticall to the doctor-patient relationship. So this column is just not capable—by definition—of answering every tech questions with
h d og e so cr to t -p en ns o t s c
a high degree of accuracy. But here it goes anyway. Rather than agonizing about not being able deliver definitive, finite answers to questions
like “why is my idle rising” or “where is this noise coming from,” we’re going go ahead and run with the notion that questions beget questions beget the answer. This isn’t a new concept. It goes back to the genesis of Greek philosophy and the Socratic method of asking a series of rational questions to spark ideas and dialogue and get down to the honest truth. So here it goes.
Rising Idle and Raising Questions About 4 years ago I purchased a 1975 R 90/6 with about 48K on the ODO. The bike had been sitting in a barn for about 15 years and needed a lot of attention but I was very excited to own a classic airhead. The bike had not been properly stored so the gas tank, carbs etc. were in poor shape. The carbs were pulled and sent to Bing to be refurbished while I went through the rest of the bike. After about 2 years of novice restoration the bike was running and has run very well ever since until now. Recently, on a short run around town, the bike began to idle at an increasing rate topping out about 4,000 RPM. Otherwise, the bike runs smoothly as if the throttle is simply being opened. A check of the throttle cables, choke settings etc. did not uncover a problem. Now, when the bike is started with no choke it will within minutes slowly begin to climb in RPM’s without touching the throttle. The longer it runs the faster the idle speed. I am baffled by the quick change and cannot determine the problem but think there is an air leak in one of the carb bodies that is allowing air into the sys- tem but I have been unable to locate a leak. Have you heard of this problem in the past? Any suggestions on what to check would be appreciated.
Sid Welch # 118737 Clover, South Carolina Thanks for your question Mr. Welch. I’ve
actually been through Clover. It’s a lovely place—one of the hidden jewels of the Carolinas. This is a very common question and my
answer has both nothing to do with the question, and everything to do with it. It’s all about the methodology. First, the long answer. And by that I really
mean a long string of sub-questions, a la the Socratic Method, 101. Did you correctly set your timing? This
56 BMW OWNERS NEWS September 2015
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