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Tach Screw Completely Stripped

jacksondee

CB750 Enthusiast
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Yes, totally and completely stripped.

It was held in there with a very very large amount of gasket sealer. In fact, the entire cylinder head cover was held on with an intense amount of gasket sealer.. Seems the previous owner didn't want to but a new gasket, or hit a snag and used an ugly amount of the stuff to get bye..

What do I do about the tach screw? Take the head cover off again, then tread it one size up and get an appropriate screw?

This said, the cylinder head cover screw on Intake 4, isn't completely stripped, but when it gets all the way down and I want to give it one more little half turn to maike it just a bit tighter, it slips and pops and won't allow me to get it down all the way.

I'm assuming too both these issues have to do with a good seal and might be why I'm getting 90psi compression on every cylinder right now? Maybe?
 
Valve cover bolts have no affect on compression. Rings or valve leaking issue is what you will have to go after for the low compression. I am assuming this is a sohc motor in which case you need to pull the motor to remove the valve cover to fix the gasket and stripped thread issue. In the head I would suggest heli coil but you may be able to use a slightly longer bolt and catch a couple threads at the bottom of the hole. The tack screw also may be able to be heli coiled but I dont suggest doing it on the motor because it will impossible to do the drilling and threading without getting metal into the motor. If you have low compression sounds like you need to pull the motor and tear down to see what your issue is.
 
Its a 1981 DOHC CB750F

I checked compression two weeks ago and had between 130 and 150 on every cylinder. Then I checked and adjusted valve lash. Now compression is 90 on each cylinder. I saw on another forum that simply getting a slightly longer tach screw fixes the problem. I am scared for the cylinder head bolt.. I am also scared to pull the motor! It ran fine all last year until I broke it down a it this winter to start messing with things. I am starting to regret that now!
 
If the compression dropped after the valve lash adjust then you got the valves too tight and holding valves open.
 
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