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A Guide to Valve Adjustment

All you need to know about adjusting your motorcycle valves

  1. Mouth
    A Guide to Valve Adjustment
    By Zebee Johnstone (with additions by Murray Dawson and Alan Pennykid )

    Theory - why do the...
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    KumuduG likes this.
  1. Hijacking to ask a question. I tried to do my valve clearances today. First time. But i have some questions. Firstly. I dont know what type of valves i have. Its an 07 honda cbf250. It didnt seem to be poppets. It had what i assume are cam lobes. http://www.lunatipower.com/Images/Tech/Cams/LobeLiftSmall.gif
    I downloaded a workshop manual for a cbx250 twister but its not translated well. I dont know what kind of valves i have.

    Secondly. When i put the feeler gauges beneath what i assume are the camlobes i could not get them through all the way, on any of the valves. Not even a 0.02mm. When inserting feeler gauges are they supposed to be able to go all the way under?

  2. Good write up Zeebee & crew . Another simple way to find the back of the camlobe is to do one cup at a time.Adjust the exhaust valve when the inlet valve just closes. Adjust the inlet valve when the exhaust valve just opens . Motorcycle cams generally have good duration, which means they slow ramps from the base circle of the camlobes. So if you adjust your clearances past or before the back of the lobe/base circle you will have increased clearance.
  4. Auto spell buckshot got me again. I meant cyl not cup
  5. Got me again
  6.  Top
    • Agree Agree x 1
  7. Are replacement shims meant to be smaller than the original shims?
    Here's my calculations .
    (Current valve-specified valve) +current shim
    FR: (.06-.15)+2.06 =1.97
    FL: (0-.15) +2.07 = 1.92
    BR: (.09-.12)+2.08 = 2.05
    BL: (.08-.12)+2.07 = 2.03
  8. Yes to increase your clearance you need smaller/thinner shims. Are you going to set your clearance to the high side of the specs? I would double check your clearance on FL if you are saying it has no clearance and especially if your bike has been still running. Some times it can be hard to get the right angle on the feeler gauge.