Cam Chain Replacement Question
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  1. #1
    Senior Member jannaruto's Avatar
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    Cam Chain Replacement Question

    Hey guys,

    Having replaced my cam chain I have a very stupid question about
    The manual says put the crankshaft at TDC on the COMPRESSION STROKE aligning the T mark with the arrow and the top sprocket line with the relative arrow

    What they exactly mean with compression stroke? I dismounted the whole head to replace a gasket and so the piston moved a bit up and down when trying to remove the stator
    With COMPRESSION STROKE they mean basically when the piston goes UP right?
    Because:
    Piston goes down = fuel and air enter
    Piston goes up = compression
    Piston goes down = because of explosion
    Piston goes up again

    But when you dismount everything you "loose" track of the compression stroke right?
    Or I should dismount again the top sprocket and make another full turn of the stator in example?

    Hope my question is clear

  2. #2
    Senior Member admiral's Avatar
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    If you align the mark on the cam sprocket and the mark on the top of the cam sprocket opening your piston, valves, and crankshaft will be in the correct engine timing. You can use this same system when you adjust your valves during routine maintenance.

    If the marks do not line up, then you have to move the cam chain forward or rearward until the marks line up. I think forum member elime has a similar picture.
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  3. #3
    Senior Member jannaruto's Avatar
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    Quote Originally Posted by admiral View Post
    If you align the mark on the cam sprocket and the mark on the top of the cam sprocket opening your piston, valves, and crankshaft will be in the correct engine timing. You can use this same system when you adjust your valves during routine maintenance.

    If the marks do not line up, then you have to move the cam chain forward or rearward until the marks line up. I think forum member elime has a similar picture.
    That's what I did, align the T with the arrow mark and the line on the top sprocket with the arrow mark
    Everything was aligned together, that's what I did

    My question came from the specification of COMPRESSION stroke, I guess with head dismounted and re-mounted, cam chain removed etc etc there is no more compression or exhaust stroke, you need first to re-attach the timing chain correctly and then the valves will start to move again creating the compression and exhaust stroke right?
    So I could remove technically the cam chain, spin the stator for like 10 minutes with my hand, re-align all the marks (T with arros and line with arrow) and everything will still be 100% synched right?

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    Senior Member admiral's Avatar
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    My question came from the specification of COMPRESSION stroke, I guess with head dismounted and re-mounted, cam chain removed etc etc there is no more compression or exhaust stroke, you need first to re-attach the timing chain correctly and then the valves will start to move again creating the compression and exhaust stroke right? Yes


    So I could remove technically the cam chain, spin the stator for like 10 minutes with my hand, re-align all the marks (T with arros and line with arrow) and everything will still be 100% synched right? YesThe only purpose of the cam chain is to move/operate the valves. With the cam chain removed, the rest of the engine will move but not the valves (crankshaft, piston). When the marks are lined up the piston will be at Top Dead Center (TDC) on the compression stroke and the engine will be in the correct timing.
    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

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    Senior Member Tweaker's Avatar
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    In order to spin the motor with the chain off I think you may need to remove the spark plug because the valves will remain in what ever position they were in before undoing it and if they are closed it will be full compression. Also a 4 cycle engine has two top dead center positions. To be on the compression cycle both valves need to be closed. If you rotate the piston around to the top and one of the valves are open you are not on the compression cycle.
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    Senior Member jannaruto's Avatar
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    Quote Originally Posted by Tweaker View Post
    In order to spin the motor with the chain off I think you may need to remove the spark plug because the valves will remain in what ever position they were in before undoing it and if they are closed it will be full compression. Also a 4 cycle engine has two top dead center positions. To be on the compression cycle both valves need to be closed. If you rotate the piston around to the top and one of the valves are open you are not on the compression cycle.
    True but as said the cam chain was not connected since was in the replacement process, once you align the top sprocket with the line and arrow they will be automatically on close position, then you align the stator with T mark, and put on the cam chain, so you will have both lines aligned with both arrows
    I guess this is correct
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  8. #7
    Senior Member admiral's Avatar
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    When the cam sprocket is installed, (the cam sprocket only goes on one way) it is synchronized with your crankshaft already. Unless the cam chain stretches or skips a sprocket tooth, or the entire engine was taken apart and put back improperly your cam sprocket and crankshaft T Mark should be in synchronized alignment. When you align the cam marks with each other you don't need to worry about the T Mark on the Flywheel/Stator. Then all you have to worry about is lining up the cam alignment marks.
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    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

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    Senior Member jannaruto's Avatar
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    Quote Originally Posted by admiral View Post
    When the cam sprocket is installed, (the cam sprocket only goes on one way) it is synchronized with your crankshaft already. Unless the cam chain stretches or skips a sprocket tooth, or the entire engine was taken apart and put back improperly your cam sprocket and crankshaft T Mark should be in synchronized alignment. When you align the cam marks with each other you don't need to worry about the T Mark on the Flywheel/Stator. Then all you have to worry about is lining up the cam alignment marks.
    Well when I changed mine like 1 month ago I dismounted the head to change gasket and removed both stator and logically the top sprocket
    So I just tought to ask again XD
    I will check anyway again the alignment maybe these days because I opened another kinda interesting topic about performance loss...
    Maybe you can help?

  10. #9
    Senior Member admiral's Avatar
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    I want to add this to my post but the forum or my computer isn't letting me edit a post.

    When you have the cam marks aligned it wouldn't hurt to look and verify you're flywheel/Stator timing mark is in the correct position.
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    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

  11. #10
    Senior Member elime's Avatar
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    I tried to add my pictures but it wouldn't let me.
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    Long live the internal combustion engine!

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