Topic: Just rebuilt top end on CB750K3... won't turn over

[jpmire11]

So I picked up a 73 cb750. I just recently replaced the top end gaskets and piston rings due to the piston rings being fried and causing the bike to foul the two right plugs and smoke blue. Now that I have put it back together I have run into a little bit of a problem. I was attempting to start the bike ( kick it 10 times then try the electric start) I did this process about 3 times when the engine locked up. It sounded like metal hitting metal. So I assumed I didn't time it properly. So here is where it gets interesting. I pulled the engine back out. Pulled the valve cover off, rocker pins and rocker arms. The cam sprocket has two bolts on it. One of the bolts is on the bottom side of the cam. I can't get the bottom bolt out because it is hitting the head. I once again tried to turn the engine over using the kick start but still no movement. I was under the impression that I should be able to spin the engine once the rocker arms where off? Do I have a bigger problem here than I originally thought? Could something have fallen into the bottom end and caused it to seize?

[orkid1989]

have you tried rotating the motor in reverse with the bolts in the points cover? and how is the bolt hitting the head? pictures would probably help aswell

[ekpent]

So just to add more info,you you able to kick the bike over approx. 30 times lets say and approx 3 times you also spun it with the electric start. We would think that if something was totally amiss in the top end it would have happened during the first revolution or two.Did the engine lock up like 1/2 through a kick on the starter or while you were on the button?.Almost seems like if you had ALL the lifters and rods out,cam chain adjuster out, that you should be able to free the cam chain from the sprocket and move it and the cam around. Kind of rusty on top end right now ,lets see what the next guy says.

[TommyRocket]

I imagine "hitting the head" means that he can't get to the bolt because of the angle of the camshaft.

Disclaimer - I'm not real familiar with the SOHC 750, don't know your specific problem/situation, and may be legally drunk, but...

You may be able to loosen the cam chain enough to get it off of the sprocket by loosening/removing the cam chain tensioner and you can always cut the chain if you have to.

[ekpent]

How drunk are you Tommy ??     Good advise though

[Patrick]

Are you sure you didn't bump it into gear?

[ekpent]

Are you sure you didn't bump it into gear?

Funny you mentioned that Patrick because as I was pondering his situation, I thought what if he snicked into gear by mistake.

[Patrick]

BTDT