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Thread: Valves setting procedure for OHC engines

  1. #1
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    Default Valves setting procedure for OHC engines

    Over Head Cams With Rocker Arms

    AH... now we get to the whole purpose of this page, how we adjust the valves. The engine must be dead cold before we can adjust anything, so let it sit overnight. First, we will Find TDCneed to find Top-Dead-Center(TDC) of the compression stroke of the cylinder to be checked. Remove the gas tank, the covers to the valves and the cover to the nut on the crankshaft or flywheel. Turn the engine over until you see the intake valve go down and then up. There will be a mark on the crankcase and a "T" mark on the flywheel. When those two marks align, the engine will be at TDC and both intake and exhaust valves should be loose.

    If you can't get a wrench on the flywheel nut don't worry. You can turn the engine over by jacking the rear wheel off the ground and putting the transmission in top gear. Now simply turn the rear wheel to turn the engine. If you can't find the flywheel marks look at the intake valve as you turn the engine over in the forward direction. When it goes down and then up, take a long thin screw driver and stick it down the spark plug hole. Continue to turn the engine over until the piston touches the tip of the screw driver. Continue to turn the engine. Be careful not to jam or bind the screw driver in the spark plug hole. The piston will push the screw driver up. When it stops and starts to go down, that is TDC of the compression stroke. This will work on all piston engines.

    Tappet ScrewNow we are ready to check/adjust valve clearances. For engines with rocker arms and screw type adjusters, take a feeler gauge of the right size and place it between the end tip of the valve and the screw adjuster. If it is out of specification use a wrench or Valve Adjusting Tool to loosen the screw and change it. Sometimes you can use a regular wrench and screw driver to adjust things and sometimes you must have the special tool. When you push the feeler gauge between the valve tip and the adjuster screw there should be a little bit of resistance. One way of doing it is the go-no-go way. If a .003" feeler gauge fits but a .004" feeler gauge does not, the clearance must be .003". On most engines the intake clearances will be tighter then the exhaust clearances... but not always! Sometimes they are the same. I have never seen an engine where the exhaust is tighter then the intake.

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    Thanks bhai very informative

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    nice info (Y)

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