83 KZ550M (LTD) Cold natured

I've only owned this bike a couple of months and got it running well enough for test rides. I've put about 17 miles on it but I'm still not happy with the overall running. Seems very cold natured. Starts easily with choke but I can't touch the throttle for at least 2 to 3 minutes or it just coughs and dies. Once it's warmed up enough to get rolling it seems to take another 1 mile before there is very little to no hesitation. I can rev it to the redline in 1st and 2nd (all I tried). But it still seems to me to be sluggish. Idle is perfect at about 1200 RPM. Now this is the smallest bike I've owned in a few years and I don't expect it to throw me back in the seat but still seems a little "thin". Bike sat about 5 years (guess) prior to me buying it. Now I've revived dozens of old bikes and I think I'm pretty good with carbs, especially CV.

Here is what I've done so far:

1. Fresh oil and filter change
2. Pulled and cleaned carbs and enrichener circuits. These were the dirtiest carbs I've ever seen on a vintage bike.
3. Set float levels. They were set way too low when I got it and found a couple of stripped float bowl screws. I'm not the first inside of these carbs.
4. Synced carbs. Once I got them clean they synced up nicely.
5. New NGK plugs.
6. Checked for cracks or vacuum leaks. Doesn't act like a vacuum leak because idle is perfect and return to idle is immediate.

Now I'm ready to pull the carbs and clean again because in my mind I don't think they are perfect yet. But before I pull that trigger I tried a couple of other things for a sanity check

Just ran compression check and all 4 are within 5 lbs of 150 PSI.

Here are the plugs from left to right 1, 2, 3, 4, thumbnails. Click to see larger. This is after a warm up and ride of about 10 minutes both running hard and around town riding, then cut the ignition. Two middle ones look fouled in the pic but dry and just look rich in real life.
To me 1 looks lean and 4 looks how a healthy engine should. Nice tan electrode insulator.

Before I start anything I'd like someone else opinion on next step or diagnosis.
Thank you.

First thing's first: Have you adjusted the valve clearance? If not, do that before you pull too much of your hair out messing with the carbs.

The rest of this is assuming that you have:

Good compression, sounds like your motor is in good shape. Unfortunately that means may be running leaner than intended if you're running E10 gas through it.

Have you adjusted the idle mixtures? How many turns out are you? If more than 3, you might want to go up a pilot jet size and put a couple of 0.5mm shims under the jet needles. (you can bump up the main jet too if you plan on spending a lot of time at WOT).

A little trick is to cover half of the airbox opening with duct tape and go for a little ride. Does it run better throughout the throttle range (except perhaps WOT)? If so, you're too lean across the board.

Conversely, try removing the airbox lid and/or filter element and riding briefly. Runs better? Then you're too rich across the board.

Your symptoms sound like too lean though.

Since I have the tank off and spark plugs out I'll check valve clearance.

Yes have to run E10 because that's all I can get here.

Idle mixture screws are 2 1/2 turns on all. I did not do the idle drop method yet, because idle is so good, but I should just to confirm that the idle circuits are working as expected.

Do not expect to spend time at WOT I'm too old for that. Just want good ride ability. But I do want to hit WOT and expect it to respond when needed.

As for duct tape on the air box I usually use a single layer of those blue paper shop towels and in this case it ran but was sluggish and went too rich. With no air filter it was of course too lean even with the shop towel. I'll have to try that duct tape trick. Air filter is old but not dirty and I have replaced the foam seal.

I was thinking about shimming the needles next since idle is good. It's just off idle and mid range where it seems sluggish. Once above about 5000 rpm seems fine.

Forgot to mention bike only has 9300 miles and charging system works perfectly and has a new battery.

Thank you so much for the suggestions. I'm more used to working on Honda's but a CV carb is a CV carb. Not having much experience with Kawi I thought I should ask people who are familiar with them. My son has a KZ1000 but we cammed it and put smooth bores and a rev limiter. So it's nothing like this one. Last KZ I had was an 82 750 and all it needed was brake and electrical work. It ran like a dream but I sold it. I miss that bike. LOL

Little bit of an update. I tried running it today only this time I used my non contact thermometer and found the middle two cylinders a lot colder than 1&2. Spark is good on all 4. Pulled the carbs again and while draining them the middle two had virtually no fuel in them. Pulled the carb bowls and found middle two float needle seats were clogged with that same white flaky stuff I found in the petcock earlier. Yes I have a fuel filter now. Cleaned them out and started to flush the fuel rail and fuel hoses. Then I got hungry and stopped working for the night. I intend to just re-clean the carbs and check them over again. These carbs are easy to remove and install but those air cleaner hoses are a PITA.

I picked up and sold a 550 shaft. Carbs were as bad as I've seen. I had to use my smallest jet drill to clean the pilots. When I got it running and synced the carbs, It ran great. 1/4 choke and it would fire up and idle. When it would raise in a few seconds, I turned the choke off. The guy that bought it said "someone has done the carbs", I said I did. I'm convinced that was all that was needed. It stumbled and rattled like hell until I dialed the carbs in.
Steve
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882

Ok I feel like such a noob. I made so many rookie mistakes with this bike. It's not really complete yet, as I am soaking the boots in xylene and wintergreen oil right now, but I stuck the carbs back in and fueled them up. It started immediately and after a few seconds I had to back the choke off to 1/2 way. Even with no air cleaner it ran smooth and grabbed revs like a new bike. So I got it running on all 4 now and sounded great. I'm sure it will run a lot better with the air box hooked up. This was only a check to see if runs on all 4 now.

Long story short I'm an idiot and it's probably not cold blooded anymore. Thanks to all who replied, Especially swest. I read his posting and realized that it is not the nature of the KZ550 to be cold natured or running poor when cold.

Rookie mistakes:
1. Didn't clean the petcock or check it's function prior to fueling it up the first time and trying to test run. Turns out the petcock was filled with white deposits (ethylene?). FYI cleaned up easily when I took the petcock apart and soaked it over night in plain white vinegar.
2. Didn't get the enrichener circuits clean the first time I cleaned the carbs.
3. After cleaning the petcock I tried a test run with no fuel filter. I know better no excuse other than I messed up.

No one can beat yourself up more than you. Enough of that. Time to get it done and ride the piss out of it. :woohoo:
Steve

Update: I just put the carbs back on the bike and test rode it. That thing pulls hard! It's a little rocket ship...I had no idea a 550 would run like that. Pulls fine off the line but get it above about 4000 RPM and it really starts pulling hard. I had to back the idle down about 1/2 turn but smooth as silk at 1000 RPM. Next I'll ride it around a bit and just to make everything is "run in" then I'll look at carb sync again.

Thanks to all who pointed me in the right direction.

+1 on SWET's comments. You were brave enough to jump in, and noble enough to own your mistakes. Mush on, it is how we learn. Nice job. Most the bikes I buy have gummed tanks and carbs. It is what humans do: "I'll just try it and see if it starts" and they take all the garbage in the tank, the lines, the petcock, the fuel bowls and jam it into those tiny little orifices in the carbs. Most common problem in the world.
The 550 are impressive for being such small displacement bikes. Very satisfying to rider IMO. Nice job