81 kz440ltd idle's on one cylinder. please help!!

i have been fighting this bike for weeks now eliminating diff little problems. so here is where i am at. the bike has new coil, carbs have been rebuilt and cleaned many times, float levels are ok, valves adjusted,new plugs and wires. so the bike starts up and runs with full choke i can shut choke off and it stays running. but the right cylinder is clearly hotter than the left.i can pull the plug wire while running and no change(unlike at 5k-6k rpms where u can hear left cylinder cuts in and out while i pull the plug wire) left pipe blows cold air like its not firing at idle. if i rev around 15k-2k rpms left pipe starts popping/backfiring then it seems like it fully kicks in and reves up to 6k0-7k rpms on its own. so i figure the left cylinder is not getting fuel at idle, right? when i pull the left plug its normal and dry. i mean i am pretty knowledgeable when it comes to cars but this is new. theirs not to much to this and but im missing something. any help and suggestions are appreciated.

Can noone help? I have also sprayed wd40 allover the carbs and no change. Im I need of assistance.

if the plug is dry and you are positive you are getting fire at all times to the plug, then its got to be fuel, something in the carb has got to be wrong. you may want to go to wiredgeorges site, he is the carb guru

I'm no expert, but I did spend alot of time troubleshooting my kz400.

1. At idle, when you pulled the left plug, did you hold it against the engine casing to see if you had a spark?

2. The rest of the symptoms seem to point to the pilot circuit on your left carb ( I know that's not what you wanted to hear). I'm not familiar with the carbs on the 440's but if you didn't pull the fuel/air mixture screw and try and get all the gunk out with carb cleaner and compressed air, it's almost impossible to clean that pilot circuit.

Good luck

If not already done, would remove plugs, connect caps, hold plug bases against engine fins (to ground the plugs), spin engine over with ignition turned on, and inspect spark quality. This to indicate whether there's a good fat spark.

Perhaps the battery is not fully charged, resulting in insufficient voltage at lower rpm, but beginning to fire at higher rpm as the charging voltage increases.

Could also measure voltage across battery terminals with engine off, again at idle rpm (look for 12+ volts), and again at 3000 rpm (look for 14+ volts).

Good Luck!

Thanx for the replys. I am getting spark through out the rpm range. So ill tear down the left carb again and see what that does.

thanx everyone the bike runs better it was the pilot jet, cleaned it and runs on both cylinders at idle now. still have order intake boots and sync carbs but that should be it.it will be a while befor i can ride it seeing as i have a broke leg and 8-10 weeks off of it but that more time tuning it. but thanx again for the help.

Problem is the pilot jet. This was clear from your symptoms. The #35 Keihin pilot jet will have to be cleaned as there are no replacements. K&L sells a wire set for cleaning jets. I think www.z1enterprises.com can sell you one. The smallest wire will fit into the hole and that is about the only way to unplug and clean one of those pilot jets.