Just bought a 1978 KZ200 with 4000 original miles on it. I had to install new carb float and jetting is stock.
Set the float level by the tube method. Set timing with timing light and everything has been gone through, adjusted to stock factory specs.

Bike starts right up and never needs choke to start. Idles fine but once the engine is fully warmed up and I come to a stop it stalls out and will not hold idle. I adjust the air screw out to about 2 1/2 turns ( stock is supposed to be 1 1/4 turns out)
and turn in the idle speed screw to try and keep idle but I keep fighting between the two adjustments in an effort to keep it from dying at idle but to no avail.
When I check the plug after running on idle circuit, it is black and sooty. However the bike runs just fine off idle to full throttle and the plug reads excellent in that range.
I tried lowering the needle by one position, and adding one step leaner idle jet and although it seems to run a little better it still ends up loading up at idle and stalling at stops from the rich condition at idle. Just can't seem to get the idle circuit leaned out enough it seems.
Would sure like some expert advice, I am a pretty competent mechanic but I am stumped.

 

I had to replace my carb boots on my KZ1000 because of cracking and air leaks. Mine were really noticeable.
Basically anything rubber should be checked for air leaks
You probably already know about the starting fluid leak detection method. While the engine is idling, spray a small mist of ether around connections and hoses. If the engine ramps up in rpms, there is a leak. Around the carb area only of course.

then go back to your stock carb settings if you had to replace the boots and repeat your tuning methods.

 

thanks, yes I have a new carb intake boot and nothing is leaking around that or the Airbox boot.
Last time I ran the bike for testing I even removed the air filter element and it's still rich as can be at idle

. I rev the engine at idle and the little drain hole under the muffler is spewing out black soot. I have a genuine Keihin one step lean pilot jet ordered and will see if this makes a difference. I do have a 35 pilot in there currently but is an aftermarket and I hear that those can be off compared to original jets so I'm hoping this helps. just did a compression test and I am getting 165 psi with the engine cold .

 

Have you removed your muffler or checked that things are not plugged there? (Was thinking of possible excessive back pressure from the exhaust.) The engine cannot breathe.

Just tossing out stuff and I think that you on top of it.

 

I think I will do that yes. I just got this bike a couple months ago so who knows what went on before I owned it.

 

I seem to be making progress.
I went from a 110 mainjet down to a 105, idle jet from an aftermarket Keihin 35 to a genuine Keihin 35, (bleed holes of genuine jet definitely smaller ) Needle jet clip set to leanest slot (top)

No longer a sooty black spark plug , bike holding idle after warmup so far.
With bike at idle, when I slowly roll open throttle it wants to die, so my transition from idle circuit to mid is lean, so moving the needle clip down a notch should clear that up.
Lesson learned ? This particular antique carburetor (Keihin PW26 ) in my experience is sensitive to oem jets and all jetting circuits working together , ie,
the circuits seem to overlap one another more than reported in the kawasaki service manual and on many carb tuning blogs/sites.
Especially the idle and mid range circuits.
Thank you for all input.

 

A bit of a long shot..... but did you get this resolved? I have the exact same symptoms on my Z200. Winding the air screw out to almost 3 turns is the closest I can get to it not stalling at idle. Currently on the standard 105 mains and the middle rung of the needle.

 

Thanks for your reply... yes I have my jetting at stock also and as a matter of fact just the other day I turned my air screw out three full turns just like you and it does not stall out as easy but sometimes my RPMs will shoot up at idle indicating that it is too lean .....this is a constant struggle and just now I ordered a new needle and seat to see if this helps. I'm thinking that maybe the gas level in the bowl is too high sometimes because I believe that the gas is leaking a bit past the needle seat. (once in a while after shutting the bike off and coming back to it I notice a puddle of gas coming out of the bowl overflow tube onto the ground. ) If this doesn't do the trick, I am convinced that what we are experiencing here is heat percolation of the fuel in the float bowl after the engine gets heat soaked. I say this because the engine runs just great even at idle until the engine gets hot. I'm trying to figure out how to put a plate of some sort acting as a heat shield between the carburetor and the engine head.

 

That is just like mine. It dumped fuel on Saturday despite the float definitely not being stuck. I suspect i now have fuel getting past the piston rings as the oil level is higher than it used to be. Using the tube method I have it on what i believe is 5mm below the face of the carb in line with the clip. I'm on a new set of 38 pilot, 105 mains and a D46 needle, which is a keyster rebuild set for a standard z200, so there is no good reason for the pilot circuit to be so rich. I don't think the pilot can be downsized anyway on the PW26, or at least i haven't found a smaller one for sale, so just as a test I'm going to drop the needle a rung, just in case it has some effect on the pilot circuit.

I have ordered a B8ES as i'm currently on a B7ES, and for the sake of £13 i'm changing the condenser too, as i'm now just throwing what i can at it.

I cant get my head around which is wants to die at the smallest touch of the throttle, and i mean the tip of one finger. On the open road it behaves fine until you reach a junction and pull the clutch in then it just dies.

There is a guy on the facebook Z200 group that is running a VM26 from a CG125, and that apparently works fine on the standard CG125 jets, just needs an adaptor made up to slot into the rubber plate on the head.

On a positive note between the two of us we might stumble upon the right answer.

 

Sounds good I'll let you know if I make any headway.