KZ650 will not start

I need help - bought a KZ650 in a bad shape and want to make it a runner. Rebuild the forks, replaced all fluids, fixed the electric system, installed new brake pads, new tires, spark plugs and drive train and so on. Unfortunately I can't get it to run. Engine turns, compression is good, got a spark, cleaned the carb, but still nothing. The weird thing is, that it fires up sometimes and runs for two seconds. I noticed that when trying to start it, it doesn't go through any gas – I would expect if you run the starter as long as I did, it would suck some gas through the engine. I have a transparent gas line and can observe it pretty well. The gas line is not clocked either, when I open the drain, it flows right through. Any advice anyone? Thanks!

Sounds like a carb issue, if the bike has sat for a long time then it will take an overhaul of the carbs and not just a simple cleaning.

What year KZ650? Different years had different carbs. Ed

It's a 1978. I had the carbs apart - cleaned everything and checked for wear and tear - the bike just has 13k miles on it, so it's hard to believe that parts are already worn out. Thanks for your help!

TheHolk wrote:

It's a 1978. I had the carbs apart - cleaned everything and checked for wear and tear - the bike just has 13k miles on it, so it's hard to believe that parts are already worn out.

I agree. The '78 carbs are pretty much the same as the '77 - no diaphragms or other rubber bits to teat or split. Are you sure the choke it working ok? The KZ650 don't like to run cold with the choke off. Also, I'm assuming it has the stock airbox & filter. Is that the case? Ed

yes, everything stock. Think I clean the carb again and hope for a different result (well, isn't that the definition of insanity). Will keep you posted.

Welcome.
Have you confirmed that you have spark on all 4 plugs?
Do they look wet from gas?

If you had the timing advance mechanism apart for cleaning, and you reinstalled the cam 180 degrees off, you will get spark at all 4 plugs, but at the wrong time. An easy way to check is to swap the green and black coil wires, then try to start her up.

With 13000 miles, she will have lots of life left in her.

Had a similar problem on my z650b3.
Tried everything from changing coils,rebuilding carbs,new plugs,leads,etc but still was a nightmare to start.
When it eventually did start it ran fine till the next time i tried to start it.
One day for some strange reason i checked to see if all the choke plungers were fully opening with the choke lever and found that No 4 plunger was not fully open.
Removed the screw and spring that holds it on to the carb bracket as this acts as a stop and it let the levers open that bit extra and it started first time.
If you are sure you have a good spark and are getting fuel to the carbs then i would give this a try as it costs nil and you might get lucky.
I bought a spare set of carbs of Ebay to keep for spare parts and two of the plungers were ok so bike sorted and dont have to remove screw and spring to start her.
(you can also lift plunger up by hand to save removing screw but No 2 & 3 plungers are hard to reach)