TOPIC:

I just reinstalled the carbs after a friend did an untrasonic cleaning on them and supposedly reset the fuel screws to factory settings. Bike starts OK but idle goes up to 4 thousand. If I rev it, idle will drop to a thousand or so. I took it for a ride, continually revving it to bring idle down. Got it warmed up, tried to set idle. Bike was idling about 900 stumbling not wanting to run. Turned idle adjuster, nothing happened, turned it again, nothing, turned it again, idle rose to 5000. Turned idle down, nothing happened, turned again, nothing, turned again idle dropped to under 1000. I loosened both throttle cables on both ends to take the cables out of the equation. No difference, BUT I noticed when I put the choke on it runs normal. I should add I just changed the exhaust from 4 in 2s to reproduction 4 in 4s and I didn't change the jetting. Bike ran pretty good before I had carbs cleaned. I actually only pulled them to check the float levels and figured I'd have them dunked while they were off. Any insight and or advice will be greatly appreciated.

Also... I did check for exhaust leaks just with my hand and listening and doesn't appear to have any leaks. I did change the copper crush gaskets.

Vacuum leak from the carb boots?

I'll go get some carb cleaner and check that next. I just noticed I forgot one of the screws on the bottom of the number 2 boot on the manifold side... .tried for a half hour to put it back in... not an easy task. Not sure if that would do it or not.

God... pulling those carbs is torture. Installed the missing screw on the intake side boot and found some cracked boots on the airbox side. Just bought 4 new ones from Z1 Parts. There was only one good one out of the four. If anyone needs just one single inner boot, PM me and you can have it. These are the cheap plastic ones. The bike ran pretty good before I pulled the carbs, I'm thinking I damaged these putting the carbs back on. I know I was being pretty rough on them because they were being bastards. I probably poked them too hard with a screwdriver or one of several other tools I was using. Thanks for the suggestion Nessism.

If you haven't replaced the engine side boots now is the time too. Safe money knowing they are fresh and you won't have to ever deal with leaks.

Robb2018 wrote:
God... pulling those carbs is torture
... .tried for a half hour to put it back in... not an easy task

Go and buy a Z1 Air box!!!

I was happy to find a KZ900 that still had the stock airbox. It's getting hard to find one that hasn't been converted to pods. This bike is almost completely original, so yeah, I get that it's easier to pull the carbs with a Z1 airbox but as often as I need to do that I'll suffer through it. Gives me something to bitch about.

Damn.... got the carb boots today, idle still getting stuck around 3,000 and have to rev to get it down. Also, idle is very hard to adjust. It's like you give it several turns and it doesn't do anything then turn it again and it jumps a couple thousand rpm. Very frustrating. Return spring is good, cable routing hasn't changed.... no more air leaks... what else could be causing this?

Were the carbs manually synched when installed? If the slides are too high they will allow more air into the engine and it will rev high.

Yes, they were bench synced. The thing is, I can adjust the idle down with the throttle stop adjustment but when I ride it the idle will hang up. Revving it will usually bring it back down... but then too low.

I would check my choke plungers to see if there is any leakage. I would also check if the carbs have proper clearance of the idle adjuster when the throttle bodies are completely down. (Not sure if this applies to KZ carbs but there is an instruction on how to do this for Z1 carbs.) Check the pilot fuel/air screws. Check the air cleaner to ensure it's clean and unobstructed. Check the intake boots to make sure there is no leakage. Are the floats properly set?

If that all checks out (I know you've done some of it) then I would go back to the carbs to see if they were rebuilt correctly. What was replaced? Needle jets? needles? mains? pilots? float valves? Most people don't replace the needle jets but they DO wear and allow more fuel to get by the needles, which will also wear.

choke plumgers appear to be working fine.. sprayed them with WD40. Took bike for a ride... idles 2500 to 3000 unless I'm continually revving it. Very frustrating. I'm out of ideas.