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  1. #1
    CB750 Member nsxguy7's Avatar
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    SOHC timing....please help!!

    Hello all. I'm at wits end and hope someone can help me.
    75 SOHC motor. Just did a stock rebuild. Head professionally rebuilt. Everything lines up as per the manual. #1 cylinder at TDC, notch on the cam pointing up, etc. I adjusted the valves on cylinder #1 no problem. According to the shop manual, you adjust the exhaust valve on #2 and the intake on #3 at the same time. No dice. On both cylinders, even with the adjustment screw backed all the way in, the rocker is sitting tight against the top of the valve stem. I've triple checked everything and I'm stumped. Please help.

  2. #2
    Moderator dirtdigger's Avatar
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    Remember cylinder 1 is on the left as you sit on the bike...lot of people get that mixed up. If you turn to tdc on cylinder 2 are the rockers loose? You can easily just adjust the valves one cylinder at a time, just put each on top dead center. On my high performance motors I do each lobe one at a time, turn it so each lobe is on the base circle of the cam.

  3. #3
    CB750 Member nsxguy7's Avatar
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    Thanks Digger. I knew you would chime in at some point. Yes, at least I got cylinder #1 right. I kind of finally figured out what you are saying. So if the notch on the end of the camshaft is at 12 o'clock when cylinder 1 is at TDC, is it at 3 o'clock when #2 is at TDC, 6 o'clock for #3, and so on? Thanks!

  4. #4
    Moderator dirtdigger's Avatar
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    Just watch the timing mark on the crank. Turn to tdc number 1 set valves, turn half turn to tdc number 2 set valves, turn half turn to tdc 4 etc

  5. #5
    CB750 Member nsxguy7's Avatar
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    Thanks Digger, I think I got it. One question- is it possible to get the timing off by 180 degrees or not? I say no, a friend says yes. Doesn't seem possible to me...

  6. #6
    CB750 Member cttrail90's Avatar
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    Yes you can get it off 180 degrees. Pull #1 plug and put your finger over the plug hole and turn motor over slow by hand until you start to fill compression from #1. You are now on the compression stroke. Now put it on TDC.

  7. #7
    Moderator dirtdigger's Avatar
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    If the cam is off 180 it will still run fine as cylinder 1 and 4 are paired on ignition. When cylinder 1 is on compression 4 is on exhaust but both cylinders have spark as they share coil. If you left the crank at top dead center 1 cylinder 4 is also at tdc, now if you just took the cam out and put it in 180 off then cylinder 1 would be on exhaust and cylinder 4 would be tdc compression but you would still fire because both cylinder 1 and 4 get spark at same time.

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