Hard starting on 81 KZ1000

I am struggling with this bike. When cold if you use the choke it won't start; you just have to crank it with no throttle and when it tries to start pull the choke out real slow and then it will run and you can take the choke off after 30 sec or so and it seems to run fine. If you try to give it throttle while starting it doesn't seem to help actually seems to make it worse.

When hot, if you turn it off to get gas or some other short errand its hard to start and you have to just let it cool some and then it will start but not easily. I have replaced the carb intake rubbers, coils, plugs, coil pickup and carbs and nothing really seems to help. I have checked compression, valve lash, cam and ignition timing, and all looks OK.

When I try to lean it out with the pilot jet screw with the current RS34 carbs thinking it was to rich this seems to help the starting but then it seems to lean for idle and off idle. I just went from a .8 to a .7 air bleed and this seem to help the idle and off idle as well as the starting when hot but it still hard to start. Any thoughts would be welcome.

Thanks

Have you looked to see if you have any vacuum leaks?

I have and could not find any leaks and when I put on the carb sync vacuum gauges they looked like they were all about the same. After changing the pilot air jets and a test drive I put in new spark plugs just to rule that out and the ones that were in there seemed a little on the rich side so tomorrow I am going to try to go to a little leaner main jet and see if this helps with the cold starting.

Thanks for the reply.

Pic of the plugs?
Steve

Here is the plugs. #1 is on the left and #4 on the right.

Looks lean to me. The black around the outside is oil and unburned fuel.
Steve

The plugs in the picture are not that old (new when this problem started on the original carb) and when I put on the new RS34 carb hoping that the old carbs were just not working right I stepped up the main jet going richer at 5 increments and it seems like the jet that came with which is a 125 is where it responds the best for wide open throttle. Right now it idles good, no flat spots, good wide open throttle and did not have any surging at off idle with the .7 pilot air bleed jet and the pilot jet screw at 3/4 turns out just hard starting. With the stock .8 air bleed I had to turn out the pilot jet screw 2 1/4 turns so that it would not surge at off idle (did not idle as well) but when it was at 1/2 turn out it started better but it surged pretty bad at off idle but it did idle better.

Another thing that seemed weird is if i gap the NGK B8ES spark plugs at .40 it starts better vs. the .28-.32. I thought the coils, plug wires and and or pick up might be bad but I just replaced them all with no difference. It acts like when i am starting it that its to rich but like you said the plugs don't look that rich.

What pilots do you have in there?
Steve

I haven't looked at the pilot jet yet but the manual says it is i a 17.5.

New or used carbs?
Steve

They RS34s are new. I bought two used carbs off ebay and it would run great for a while and I would have to take them off and re clean the pilot jets so that it would idle ok. I run a inline fuel filter and the screen on the needle/seat did not show any junk so when this last problem started I just gave up and bought the RS34s.

This morning i went from the 125 to the 120 main jet and it started with the choke on and it seemed to run bad with it off and when I put it back on it seemed to run ok to let it warm up. As soon as it warms up some outside i will take it out for a test drive and see how it starts when hot.

Thanks again

You start at the pilots then go to the mains. Needle clip in the center position My 33's were set up for a Honda. 2.0 slides. The pilots are at 70 not 40's as is called for by Mik so I guess the settings don't apply in my case.
I'd go # 20 pilots. Hard starting when hot is streange.
Steve