TOPIC:

My 1979 KZ650 runs great on two cylinders (Number 1 & 4)  Does anyone have ideas why the number 2 and 3 carbs would not be 
getting gas when number 1 & 4 are?   The carbs have recently been cleaned and rebuilt by a local shop that I trust.  Also, the coil
controlling number two and three has been replaced and the plugs are firing.   There are no air leaks.  The petcock has been rebuilt 
and the petcock vacuum line is connected correctly.

Ideas are appreciated.  I'm definitely not an expert in this area.  

Have you checked float levels to confirm a fuel issue ?

Which carbs do you have? 22's or 24's. Airscrew, fuel screw or both?
Check the bowl drain screws to ensure all 4 are getting fuel. It's unlikely that 2 & 3 are not getting fuel and 1 & 4 are as the fuel has to pass 2 & 3 to get to 1 & 4.
Check the airscrew/fuel screw are equally out on all 4 carbs. If the air screw or fuel screw are entirely closed on 2 & 3 then the mixture could be so far out that it won't fire. 
Just seems a bit suspicous that the cylinders that are not firing are both on the same coil, are you 100% they are sparking? 

Not yet but when I remove the drain screws no fuel comes out.  

Warren3200gt wrote:

Which carbs do you have? 22's or 24's. Airscrew, fuel screw or both?
Check the bowl drain screws to ensure all 4 are getting fuel. It's unlikely that 2 & 3 are not getting fuel and 1 & 4 are as the fuel has to pass 2 & 3 to get to 1 & 4.
Check the airscrew/fuel screw are equally out on all 4 carbs. If the air screw or fuel screw are entirely closed on 2 & 3 then the mixture could be so far out that it won't fire. 
Just seems a bit suspicous that the cylinders that are not firing are both on the same coil, are you 100% they are sparking? 

I've checked all four with a spark tester (not a multimeter) and the spark quality appears to be the same on all cylinders.  
 

Fair chance the floats have been put back in upside down on 2 & 3 then so floats can't drop to open the needle valve. 

Some photos of the carbs would be helpful.

hardrockminer wrote:

Some photos of the carbs would be helpful.

I'll be pulling them today and will post photos.  
 

This morning I pulled the carbs.  Number two is completely dry.   (I'm old and couldn't get the drain plug out previously)One, Three and Four all have gas in the bowl. Here are pictures of the carbs.  Let me know what you see and what I should be checking.  Note:  the valve needle on carb two does not appear to be stuck.  Thanks! 

I have to be honest, if these have been "gone through" I would ask for my money back. Ref the arrows on the picture - why are the jets hanging out of 1&4 with what look like very perished "O" rings and why is 2 not sitting on the stop like the others (is the float sticking?)

 

I agree with Wookie they sure don't like they've been cleaned or rebuilt. Sometimes like the old saying goes if you want something done right you need to do it yourself. I hope they didn't charge you much, I would demand my money back and never do business with them again.

They definately saw you coming, at least two emulsion tubes are hanging by a thread or two and why is there no balance tubes between the bowls?
Vm24 pumper have the bowls linked and if the floats are set so low that they don't piss fuel out the balance pipes and its 1 & 4 which have the emulsion tubes undone then that's why it's only running on those two. 2 & 3 can't draw fuel from anywhere. 
That doesn't explain why one bowl doesn't get fuel though. There must be a blockage on that carb fuel feed supply. 
Can you post a picture from each end of the carb rack so we can see the airscrews please. I wouldn't put it past them to have reassembled the carbs into the incorrect positions on the mount rail and seeing the airscrew positions will confirm either way.