Valve Adjustment Question
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  1. #1
    Member JRD's Avatar
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    I'm checking the valve adjustment on my 2008 TW200 with only 650 miles (I recently bought it used with less than 500 miles on it). Clearances are within tolerance (.002-.004" intake, .004-.006" exhaust). As I was getting ready to button it up, I rotated the engine to learn more about how the valves worked and here's what I found:



    1. with the tdc mark centered in the sight window, both adjusters are tight.

    2. after a 360 degree rotation and with the mark again centered in the window, both adjusters are loose.

    3. after another 360 degree rotation and with the mark again centered in the window, both adjusters are tight.

    4. after yet another 360 degree rotation and with the mark again centered in the window, both adjusters are loose.



    Based on my limited knowledge, this was not what I expected. The bike seems to be running well and the adjusters required no adjustment from me when I just checked them. I'm assuming that all is as it was when the bike left the factory.



    Any explanation or insight will be appreciated. Hopefully this is the way it's supposed to be except that I need to learn more about how a single cylinder four-stroke engine works.



    Joe

    SW OHIO USA

  2. #2
    Senior Member Rainman's Avatar
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    I'm no expert either, but I know that its crucial that you check the valves at TDC on the compression stroke. Any other combination of engine revolution and stroke will give you a false reading.
    If you can't find it, grind it

    1990 TW200

  3. #3
    Member Lonesome Dave's Avatar
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    It says some place on this forum, that you have a fifty/fifty chance once you line up the TDC marks. If you can't get the feeler gauge (.004) to fit, your on the wrong side and need to rotate 360 degrees. Then you will be on the compression stroke at TDC to do your checks. BUT, wait until someone else confirms this before you take my word for it!

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  5. #4
    Senior Member old mad max's Avatar
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    That's normal for a 4-stroke single................ Now if it were a smoker then it would be on a compression stroke every 360 degrees. OMM.

  6. #5
    Senior Member elime's Avatar
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    I think a better mark to use is the one on the large cam sprocket. With it you get it right every time. Simply place the mark at 12:00 as shown in the picture then adjust your valves.



    Replace the Phillip head screws with some bolts for easy removal. Get a new large o-ring in before you take the cover off in case you need to replace it. With a new o-ring simply tighten the bolts until it is metal to metal contact and then tight just a teeny bit more. Don't go any tighter though the temptation is difficult to resist. Or use a torque wrench.



    If you do your 360 degree exercise you will notice the mark is at 12:00 then 6:00 then 12:00 again. You can only adjust the valves when the mark is at 12:00.



    Long live the internal combustion engine!

  7. #6
    Senior Member RockyTFS's Avatar
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    Quote Originally Posted by JRD View Post
    Hopefully this is the way it's supposed to be......

    Joe


    Yup, that is exactly how it works. Find the mark, and if the feeler won't go in, rotate one revolution. To help avoid going past the mark, stick a pencil in the spark hole so you can tell when the piston is close to TDC.
    Rocky
    2018 TW200
    2014 BMW R1200GS LC

  8. #7
    Member JRD's Avatar
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    Quote Originally Posted by Rainman View Post
    I'm no expert either, but I know that its crucial that you check the valves at TDC on the compression stroke. Any other combination of engine revolution and stroke will give you a false reading.


    With all respect, it seems to me that if the valve is closed with adjuster loose and the adjustment is within spec it shouldn't matter which stroke it's on. A closed valve is a closed valve, or am I missing something?



    Thanks all for the feedback...

  9. #8
    Senior Member RockyTFS's Avatar
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    Quote Originally Posted by JRD View Post
    A closed valve is a closed valve, or am I missing something?


    Yes.



    The idea is to get BOTH rocker arms loose at the same crank position. That only happens at TDC on the compression stroke. Oh, BTW, there is an easy way to tell which stroke is the compression stroke....put your finger over the spark plug hole. When you get pressure the piston is coming up to TDC on the compression stroke. Then look for the mark to get it right at TDC. EXACTLY on the mark, you only have to be a millimeter off to affect the feeler gauge reading.
    Rocky
    2018 TW200
    2014 BMW R1200GS LC

  10. #9
    Senior Member silverhead's Avatar
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    suck, squeeze, bang, blow. You want to time it right between the squeeze and bang. The issue with 'a closed valve is a closed valve' is that the profile of the camshaft might slightly vary at any given part of the cycle.



    I found a photo of a TW camshaft and drew an imaginary line where maybe the intake and exhaust valves are both closed at TDC. That point gives you the proper values with your feeler gauges.



    Everywhere I drew a red circle, the valve would be closed still, but I have no idea if it would yield the proper reading with the feeler gauge. Probably close, but I never try to out-think the manufacturer.



    1993 TW200

  11. #10
    Senior Member elime's Avatar
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    Quote Originally Posted by JRD' date='19 April 2013 - 01:44 PM' timestamp='1366404294' post='74060
    A closed valve is a closed valve, or am I missing something?


    At top dead center of the exhaust to intake stroke both valves are open a little bit. It is called overlap. On high performance engines the overlap is a lot hence the rough, lumpy idle.



    Or think of it as the exhaust valve closes after TDC and the intake opens before TDC. Top dead center on the wrong stroke neither valve is closed.
    Long live the internal combustion engine!

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