rebuld problems

[jacob]

hi, i recently replaced a head gasket on a 1979 Honda cb750 dohc, after getting all the cams in, new valve shims and the timing correct, i noticed a problem, i can turn the motor over clockwise just fine but when i try to turn it over counter clockwise (witch is the direction it runs in) it turns about half way then stops like its stuck. it will turn over if i force it really hard, but i know somethings wrong. it also puts a lot of tension on the cam chain adjusters even when their loose. i also have no compression too, i dont know if that has anything to do with the problem.
if anybody could help that would be awesome. thanks

 

[amc49]

If you have whirled the engine around to check for compression you have already bent the valves. Mistimed the cams, common mistake.

Should be turning CLOCKWISE ONLY, and from the alt rotor, you don't turn engine from the ignition pulser side, it twists the advance all out of shape. AND you NEVER turn backwards, the cam chain slacked and not tight then lets the valves hit even if cams were timed right. One should ALWAYS practice to turn engine only in the direction it runs when setting timing, not doing so? Well, you see why now. Forcing it really hard bent valves, you cannot force even slightly.

 

[madmtnmotors]

+1

"force it really hard" is bad news...

 

[jacob]

If you have whirled the engine around to check for compression you have already bent the valves. Mistimed the cams, common mistake.

Should be turning CLOCKWISE ONLY, and from the alt rotor, you don't turn engine from the ignition pulser side, it twists the advance all out of shape. AND you NEVER turn backwards, the cam chain slacked and not tight then lets the valves hit even if cams were timed right. One should ALWAYS practice to turn engine only in the direction it runs when setting timing, not doing so? Well, you see why now. Forcing it really hard bent valves, you cannot force even slightly.

thanks for the reply, but i did have it timed wrong, i re adjusted and it starts up just fine. so i am guessing nothing got hurt.

 

[jacob]

also after if re timed it i did a compression test and i got 145 pretty solid across all 4 cylinders. so theirs no leakage occurring in the valves, so wouldn't that mean my valves are not bent?

 

[amc49]

170 psi is the stock compression but yours being even says probably not bent. Count yourself one of the lucky few, you NEVER force an engine to turn at rebuilding if it doesn't want to.