1978 kz750 smoke

It connects one intake to the other

That's a twin. try pinching the hose to see if it stops. You should have plugs. The ports are for sync not to equalize the carbs.
Steve

Ok. In my video I give it a light rev and it smokes is that because the rings are new or might I have damaged a valve seal

Did you plug the ports? Retighten the head? You need to get some miles on it to be sure.
Steve

Leave the tube between the manifolds in place, it is a "balancer tube" according to Kawasaki. Every early 750 twin I've seen has that tube in place all the time.

Update.... I put new rings valve guide seals and also lapped the valves new cylinder gasket and head gasket. I took it out on the highway today. It stills smokes and now I have a bad pop as well as doing highway speed it wants to shut off but when I get back to side street speed it doesn't want to die and thoughts

Soxx4u wrote: Update.... I put new rings valve guide seals and also lapped the valves new cylinder gasket and head gasket. I took it out on the highway today. It stills smokes and now I have a bad pop as well as doing highway speed it wants to shut off but when I get back to side street speed it doesn't want to die and thoughts

This is a tough one because I have gotten away with doing what you did.

However, what was the condition of the pistons and cylinders before doing all this? Did you mic the pistons and bores to see if a fresh set of rings can be used?
It can be a crap shoot to put new rings on worn out pistons and cylinder bores... just pray it doesn't use oil.
From what I see in the .mov .... it is burning way too much oil for new rings and all that rot.
I'm thinking the pistons and cylinder are too far gone and you need a .50mm over bore min with new pistons and rings.

Soxx4u wrote: Update.... I put new rings valve guide seals and also lapped the valves new cylinder gasket and head gasket. I took it out on the highway today. It stills smokes and now I have a bad pop as well as doing highway speed it wants to shut off but when I get back to side street speed it doesn't want to die and thoughts

Did you hone the cylinders?

Have you checked compression?

doing highway speed it wants to shut off but when I get back to side street speed it doesn't want to die

That sounds more like vacuum leak/carburetor problems. Has the fuel system been cleaned, bowl levels set, etc?

Make sure your gas cap vent is open or you could be vacuum locking for fuel.

Soxx4u wrote: There is a rubber hose at the intake between the carbs and cylinder head. It doesn't pop that bad just slightly. I'll try and upload another video to show you if possible.

FYI, the 750 twins have a vacuum line between the two intake manifolds (carb holders) it's an equalizer tube. It should be there for normal running.

Soxx4u wrote: Update.... I put new rings valve guide seals and also lapped the valves new cylinder gasket and head gasket. I took it out on the highway today. It stills smokes and now I have a bad pop as well as doing highway speed it wants to shut off but when I get back to side street speed it doesn't want to die and thoughts

Back when I rebuilt my 750 twin, the carbs "dried out" while I worked on the engine (I stored them empty for a couple of weeks) and ran like crap when I put the engine back together.

missionkz wrote: However, what was the condition of the pistons and cylinders before doing all this? Did you mic the pistons and bores to see if a fresh set of rings can be used?
It can be a crap shoot to put new rings on worn out pistons and cylinder bores... just pray it doesn't use oil.
From what I see in the .mov .... it is burning way too much oil for new rings and all that rot.
I'm thinking the pistons and cylinder are too far gone and you need a .50mm over bore min with new pistons and rings.

I said this weeks ago, Op didn't seem very receptive to our advice and went is own way on it.

It is pissing in the wind rebuilding a motor without checking basics like installed ring gaps and bore clearance - even a rough feeler guage test,

Did you check out the intake system he has on that thing?
Steve