I just freshly rebuilt this CB450 engine. New pistons and everything. The force needed to turn it over throughout the cycle changes dramatically. As it passes LT it gets very hard to turn later it gets very easy to turn. I attached a video in this link of me turning it over and am wondering if this looks correct. Video of Engine Turning Over
Rebuilt Engine Hard to Turn Over
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Are you turning the engine through it's compression stroke?
That is with the plugs out. I think it has something to do with the camshaft bearings because it was a little hard to turn the camshaft with them attached.
What is happening is when the engine is at top dead center its almost spinning freely and while it's going through compression and ignition it gets much harder to turn. I am wondering if this is normal?
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Sounds like it's hitting a valve with a piston. Back off the valve adjustments(loose as possible) and see if things change.
It is whenever the left intake valve is pushed it gives a lot of resistance.
I have realized that it is very hard to turn when the left intake valve is being opened. I loosened it but it's still pretty tight.
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You may as well pull the top off the motor and check the timing mark alignment, if it's off you may as well remove the head and check for bent valves.
I did a top end rebuild on a cb450, the machine shop charged extra to tear the head apart and put it back together after doing the valve job. I put the top end back on the engine and installed it into the frame. I checked the timing as well as my friend before coupling the timing chain. We got everything back together and put some gas in tank and hit the little magic button. Well it turned over to start and then really started spinning freely, nothing happened, pulled the plugs and no compression! We tore the tank back off and checked the timing again. Well low and behold, the machine shop mistook a casting mark on the cam for the timing mark as we did also for the timing mark. They installed the intake cam backwards, it bent the valves and ruined the valve guide’s. The casting mark and timing mark were hard to tell apart, pull the head. I bet the same thing just happened to you, please post you findings.
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