jetting 81 kz250 single

OK... idle is a tad high. On a single CV, there can ONLY BE TWO REASONS... you have a vacuum port on the carb, right? Look up near the pilot mixture screw. Right next to it is a brass fitting/barb. It should be connected via hose to the petcock or have a vacuum cap on it. If the hose connects it to the petcock, ensure that there are no air leaks around the hose. You may want to ensure that you have no air leaks around the carburetor by spraying the area with WD40 while the bike is running; that is, around the carb holder and not the intake to the carb. If your idle changes while spraying, air is leaking in somewhere. Perhaps you should do this next step first but your throttle cable MAY be holding the throttle open to where the adjust knob is ineffectual. Your throttle cable should have VISIBLE SLACK. I know that may not sound right but it MUST have visible slack in order that the throttle not hang and the idle stay too high. You can add slack by going up to the right switch gear where the cable comes out and there will be an adjust barrel which you can turn with an 8mm open end wrench and a lock nut (need 10mm wrench). With the bike idling away at 2500 rpm, loosen the locknut and turn the barrel towards the front of the back. This adds slack to the cable. Watch the cable down near the carb (do this on the OPEN THE THROTTLE CABLE if you have two cables). If you do have two cables add slack to the return cable as well. Once the idle settles down to about 1200 - 1300 rpm on your tach (you may have to back off the idle adjust knob as well), tighten the locknuts.

Cheers WG that's sorted the idle nicely. The problem I've got now, is that after I've run the bike for 1-2 mins and stopped it, it's harder to start. It starts and doesn't idle as high, then when I stop it again it's almost impossible to start. - The next time, it basically won't start.

When I checked the plug immediately after, it was black as black.

I tried burning the plug with a torch, but it wasn't much better after refitting it. I replaced the plug and it started first time, ran and revved nice, but then when I stopped it and started it again, the above cycle repeated itself.

Although it started the first time and ran and revved great, I'm guess I need to make a slight tweak to something else to stop the plug getting fouled.

I'm not as experienced as a lot of the other guys posting on this thread but there are a few things that I have learned (the hard way) that could be causing idling trouble or "hard to restart", or "won't idle without choke":

-Make sure your carb hoses are set up correctly
-Check to see if there are any cracks in your carb holders.
-Ditch the pod filters for a stock airbox, or find a pod system that will offer enough resistance for the carbs.
-Make sure your battery is venting properly and well charged.
-Adjust the throttle cable nut/screw as necessary(a slight change can cause a big difference in idle)
-This last one sounds stupid, but make sure you have enough gas or that you switch the petcock to "reserve" when it gets low.
-Make sure spark plugs are clean.
-Just want to stress again how important and sensitive air filters and resistance are on these bikes.

Post edited by: EasyRider1, at: 2008/03/07 22:43

I would go put some miles on that bike. Fire it up, put some seafoam in the gas tank, and go run a couple gallons through it. Sometimes bikes that have been sitting just need to work out their problems on the open road.

The hard starting is due to the plug fouling. The plug fouls because of incomplete combustion. I think you have an electronic ignition... is that correct? If so, lets skip the ignition as a source of the problem. Have you adjusted the valves? Without sufficient clearance, a valve hangs a bit and you will get poor combustion. Another likely source of a combustion problem is poor spark caused by poor voltage going to (feeding) your coil. MEASURE THE VOLTAGE going to your coil. See my article at our website under wg's Tech Stuff Index called Coil Repowering. I am pretty certain you will find you are getting poor voltage at the coil. Once these two issues (valve and coil voltage) are sorted, we can relook the jetting if the plug continues to foul. You are getting real close right now... don't give up!

I realize I'm three years too late, but I'm wondering if anyone knows how things turned out for uniquezfreak, or other people who have tried going down the pods route on the z250 single? Though I'm no where up to it yet, I would like to get rid of the air box as I want to have a decluttered frame...

I realize a lot of people seem to be saying stick to the air box but.