70 kz750b4 should it run with one plug?

I've got some issues with a buddy's kz. It's popping out of the left cylinder. The carb's are synced and cleaned but the left cylinder runs rough and pops. I'm assuming that it's only running on one cylinder at times. When it's running on both cylinders the left is lean because of it keeps popping. My question is: Should the bike run with one plug cap unplugged? If the bike is on and I get the rpms around 2000 and pull the left plug the bike still runs. If I pull the right plug the bike stalls. I switched the plug wires to the opposite sides and did the same test. I got the same result. Bike runs with left cap unplugged and stalls when the right cap is unplugged.

yep,it will run on 1 cylinder.
not very well, but it will run how did it run before?

Thanks, it's a 79 not a 70. I typed the wrong year. OK, I now assume it's not getting enough fuel to that left cylinder. I'm going to try and recheck the pilot jet and passages. I may even swap left and right bowls and see if the problem moves over to the other cylinder.

Swapping the bowls wont change anything. You will have to check the float heights and set to spec

floats are set to spec(24mm from bowl gasket). I just figure if I swap the bowls I can atleast isolate the problem. My problem cylinder is the left. If I swap left and right bowls and the problem moves to the other cylinder then I know my problem will be in that bowl. I can then investigate a little deeper to figure out what
's wrong. Right?

Would perform clear tube test to assure fuel levels are actually within specs.

Measured float height is notoriously unreliable.

Good Fortune!

Is there an actual carb guide for these Kz bs38's? I'm using a guide for the xs650's.

Have you checked compression? Checked the valve clearance?
Also on the twin, you can swap spark plug leads, one coil both fire at the same time. Hows the spark quality?
Whats the plugs look like? Test for vacuum leaks?

compression is at 125/130, I didn't check valve clearance because I have no shims if the valves are off. I did swap leads and I'm getting the same result. Bike will run with left cap off and will stall with right cap off. I assume it's only running on one cylinder since it stalls when right cap is unplugged. I did check the plugs but I don't remember what they look like. I did check the intake boots and the airbox for leaks and there are no leaks.

Swapped Plugs around?
What happens when you apply the choke?
Probably going to be taking off and servicing the carbs.

I swapped the plugs and put new plugs in. Same problems. I don't remember what happens when i pull the choke. I have to problem taking off the carbs. I just want to narrow down the problem. I'm thinking pilot clogged or some fuel passage somewhere.

section8joe wrote: I've got some issues with a buddy's kz. It's popping out of the left cylinder. The carb's are synced and cleaned but the left cylinder runs rough and pops. I'm assuming that it's only running on one cylinder at times. //Should the bike run with one plug cap unplugged?

Pretty hard to do on a twin, you would have to short one of the plug wires to ground. They are in series so they usually have to fire together. If you are firing only one, there must be an internal short somewhere from one end of the coil's output winding to ground.