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Thread: ok to check valve clearance with cam lobes up instead of TDC?

  1. #16
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    Here is the spreadsheet on my correctly checked numbers.

    The new numbers are highlighted in yellow, not much difference. I'm still mostly out of spec.

    I'll have to get the shims out to see where I need to go from here.

    I'll resist the urge to put the carbs back on until I get done with valves. I had them off going through them, then decided to check the valves.

    I will probably go ahead and do the forks seals though while I wait on a tool, and then correct shims.

    Thanks to everyone for their input.

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    Tip: Never rotate the cam without a shim in place.
    Don't ask me how I know! BTW, I have a handy little tool for use if the cam drops into an empty shim bucket.
    -Pete, in Tacoma WA USA

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    Perhaps I'll throw my wrench across the yard after I get the cam set to pull a set of shims.

    Rinse and repeat.

    😃

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    Quote Originally Posted by Peder_y2k View Post
    Tip: Never rotate the cam without a shim in place.
    Don't ask me how I know! BTW, I have a handy little tool for use if the cam drops into an empty shim bucket.
    -Pete, in Tacoma WA USA
    This has me thinking....
    With the prospect of re-using many of my shims by moving them to other positions, How will i accomplish that without first having any spare shims to put in place while i move them around?

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    The tool holds 2 adjacent valves open at same time so you can swap those two, otherwise
    you will need a spare, and you probably would want a thin shim so it can be moved anywhere easily(ie a 260 or 262).
    A lot easier using a kit with a selection if you can access one.

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    Tptjg


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    Quote Originally Posted by Razorback View Post
    This has me thinking....
    With the prospect of re-using many of my shims by moving them to other positions, How will i accomplish that without first having any spare shims to put in place while i move them around?
    Measure them all first. determine which need to be replaced and remove 1 at a time those that will need replacing and see what the current size is, then replace the current shim.

    This will give a list of what shims you will need to replace and which will become eligible to be moved elsewhere.

    You would have to be very lucky to just be able to shuffle things around without a spare, and it could get very complicated. Buying a couple 2.65 shims in advance is the most likely way to get the shims you will ultimately need (60% of the time this would do the trick).

    OR. borrow my shim & tool kit with a variety of shims in it. I only ask that any shims used up 2.70 and under be replaced. Others can be swapped around for your bikes'. And pay my postage ($8.50)
    Hidden Content Dahlonega, GA. The past was good enough for us.

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    Thanks for the info Randy.
    I actually did what you suggest. I checked them all, bought the 13 I needed an then went back in for the replacement process.

    I think I "pocket posted" from my phone earlier. 😄


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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    Quote Originally Posted by Peder_y2k View Post
    Tip: Never rotate the cam without a shim in place.
    Don't ask me how I know! BTW, I have a handy little tool for use if the cam drops into an empty shim bucket.
    -Pete, in Tacoma WA USA
    Oh I know how you know

    I had to replace a bucket on my bike from making this mistake. I wanted to swap shims from one cyclinder to the other without doing the whole musical chair dance and I nicked the edge of the bucket and had to buy a new one.

    Remove cams and retime the bike.

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    I would still like to see a pic of that "handy little tool".
    Jeff Borowski . . Had 88 Venture standard, now 2011 Silverado 4x4
    There are 10 kinds of people that understand binary, those that do, and those that don't.
    Sometimes the thoughts in my head get bored and go for a stroll out through my mouth (or fingers). This is never a good thing.

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    Quote Originally Posted by Razorback View Post
    I tried using T1 and T2, but could not get a feeler gage under the lobes.
    Isn't it just as good to point the lobe straight up so there is no pressure on the valve train and then slip the feeler gage under there?

    I got readings similar to Droneh8tr, except mine are a tad tighter, therefore my numbers look believable.

    Was my measurement method acceptable?

    Thanks, Kenny
    (For archive's sake). Yes, I believe it is. Yamaha already has us measuring at different points on the base radius of the cam lobes depending on the cylinder when describing the official way to check clearance, so I see no reason why measuring anywhere on the base radius--including straight up--wouldn't give the same results.

    Here are some pictures for contemplation: https://www.venturerider.org/forum/s...13#post1046013
    Last edited by Bob K.; 03-31-2020 at 05:12 AM.

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    I thought I'd stay out of this and usually do so, and but; maybe this may help the understanding of and from a different point of view.

    Yes I agree that you should and can measure from the bottom of the lobe but; I can also say that it can also provide a problem in doing so,,, if after you check the gap you don't recheck via the book procedures, you are overlooking the limit potentials.

    Then why is that a potential problem can be missed one way and not the other?
    Because cam wear should not be found at the bottom of the lobe but it is not impossible for it to happen. Such distortions on a bike with with high mileage, been neglected or, that has overheated is not far fetched!

    It is the stems that stretch over time, the firsts few miles its stem and seats.

    If your stretch has become no longer a matter of just shims, then you need to measure the lobes well for tolerances. How do you know you are at the limits? By properly checking the gaps at the scheduled points. Eventually the stems will narrow too much and need valve replacing along with guides and seats!
    Will it matter to you, that is up to the individual.

    That's my experience for what its worth

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    Quote Originally Posted by Patch View Post
    I thought I'd stay out of this and usually do so, and but; maybe this may help the understanding of and from a different point of view.

    Yes I agree that you should and can measure from the bottom of the lobe but; I can also say that it can also provide a problem in doing so,,, if after you check the gap you don't recheck via the book procedures, you are overlooking the limit potentials.

    Then why is that a potential problem can be missed one way and not the other?
    Because cam wear should not be found at the bottom of the lobe but it is not impossible for it to happen. Such distortions on a bike with with high mileage, been neglected or, that has overheated is not far fetched!

    It is the stems that stretch over time, the firsts few miles its stem and seats.

    If your stretch has become no longer a matter of just shims, then you need to measure the lobes well for tolerances. How do you know you are at the limits? By properly checking the gaps at the scheduled points. Eventually the stems will narrow too much and need valve replacing along with guides and seats!
    Will it matter to you, that is up to the individual.

    That's my experience for what its worth
    If "stretch" is a concern, why would Yamaha have us measure at a place on the lobes for Cyl 1 and 3 that is different from the place on the lobes for Cyl 2 and 4? It seems to me that if "stretch" were a concern, we'd measure from the same place on all lobes...the location most likely to "stretch". Plus, I'm unaware of any measurements for "lobe stretch" in the service manual.

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    Yamaha would like us to adjust the valves when the piston is at top dead center(tdc). As long as the cams are timed correctly, Yamaha doesn't care where the position of the camshaft is. The lobes might be straight up or they may be off center a few degrees at tdc. Most cams are ground accordingly allowing for this.
    I have always followed Yamaha's instruction for this and have checked them after adjustment with the lobes straight up. If I had feeler gauges that would go to .0001 increments there may be a difference but maybe not.
    Yamaha also allows us a little slack when it comes to adjusting the valves. If they wanted it to be precise they could of said 'when piston is at tdc the clearance of the intake valve should be exactly .004 not a range of .004 -.006.
    Anyway this is my take on valve adjustment. I could be completely wrong.

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    Default Re: ok to check valve clearance with cam lobes up instead of TDC?

    Morning Bob, first I recognize your confidence, and I certainly see how you reasoned thru the problem

    I'm going to skip past mass, heat, and expatiation's tho they are definite considerations when developing required lash.

    The "stretch" in in the valve stem length! The stem is always under shear load hot or cold. When the power is on the constant slamming of the valve at high temperature causes the stem to elongate, this also causes the stem diameter to reduce, and as a result the guides diameter also falls out of spec!

    The longer this above mention remains out of spec the more wear to the lobe in unexpected places!

    When the required shim schedule becomes no longer adequate it is time to open and replace or regrind.
    A machinist will for example first check the stem specs before he/she chooses to lap and grind the length of the valves. Why is because he knows that if the stem is to narrow the lash will not hold spec! At which point the best fix is to replace the valves.

    And of course there's more work to do once there but hopefully this brings a broader perspective to the reasons.

    Just a reminder: the manuals only lists specs, required minimums and maximums, tools and procedures for trained mechanics, it in no ways teaches us theory or the specifics as to why or the consequences of....

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