Engine

[Parobbo13]

I have a 1977 CB750 F1 model when you use the kickstart it only turns the engine so far then stops solid but if I take the points cover of I can put a spanner on the end of the crank where the eng will turn backwards quite easily but then stops again. It will turn both backwards then forwards about 270 degrees.
The eng will turn over easily between these two points but no further.

Are these engs prone to this if so what is the problem?
Am just in the process of getting the eng out then strip it down until I find the fault.
Checking on her to see if anyone has the same problem &/or any ideas as to what it might be.

Thanks in advance.

[JamesH]

Sounds like you have a valve stuck open or possible worse. Only way to check properly is strip it...

[mike the bike]

Take the rocker cover off and see if the valves are behaving themselves.  It could be the valve timing -check if the timing marks line up, as per the manual.

[hairygit]

Will it turn with the plugs out? Worth a check, as if you have a flooding carb you could be trying to compress a cylinder full of petrol, and if you continue trying you may cause serious damage. Engine needs to come out before you can remove the rocker cover.

[Trigger]

Sounds like you have a valve stuck open or possible worse. Only way to check properly is strip it...

A sticky valve like this James 

[hairygit]

Sounds like you have a valve stuck open or possible worse. Only way to check properly is strip it...

A sticky valve like this James 

OUCH!

[JamesH]

Ha ha, wondered when that would surface. Is that from my 'one careful owner' K0 engine?

[Trigger]

Ha ha, wondered when that would surface. Is that from my 'one careful owner' K0 engine?

Nope, this is from a K4 with K2 top end, which was re-bored, new piston and rings fitted, then left on the side stand for years in a dry USA state  Had it set fire to it, to get the thing apart.

[Parobbo13]

Thanks for your replies, the next job is to take the engine out then start to strip from the top, looking for the fault as I do it. Hopefully get to the fault pretty soon then re-assemble to get back on the road.