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Thread: Inconsistent idle

  1. #16
    Registered User ebeeby's Avatar
    Join Date
    Mar 2003
    McKinney, Texas
    Quote Originally Posted by STEVENRANKIN View Post
    It is a good question for the engineers on the forum, why is it the valves have to be adjusted every 15K miles? LOL, I post this as a lark but if you think about it, what does in fact make the valves loosen or tighten? Oh sure, there is with a good oil a minuscule amount of wear on the cam, push rod and lifters. But, the valve adjusters are tight, I have yet to find one of mine loose, so, why do the valves get so far out of adjustment?

    Points I can see getting out because of the plastic wear block wearing. I can see carbs getting out of adjustment due to cable stretch and minor erosion of the needles and jets.

    Glad to hear things are running better, have fun riding. St.
    The metallurgy in 1972 was designed for leaded fuel. A side-benefit of lead is lubrication of the valves and seats. With unleaded fuel, the valves will eventually beat the seats down and the symptom is closed valve lash. Apparently, once it really gets going, the beat-down accelerates.
    However, there are examples of engines from that era not showing much in the way of closed valve lash.
    The solution is upgraded metallurgy of valves and seats. Several shops offer this such as Porter.
    1973 R75/5

  2. #17
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    The metallurgy for the '81-84 models was a poor upgrade for the unleaded fuel. The valve seats were a tool steel that didn't transmit heat well away from the valve face into the head, so the heat generated was retained in the valve face. The valve faces ended up warping or tuliping and the result was the same issue with valve lash closing up. They got the metallurgy right for 1985-on. Ted Porter is top notch with Airhead head work!!
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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