kz550 buttoned back up and won't idle

There were a lot of things to do and I did them all at once. I know you're not supposed to do this but everything was laid out in front of me at once.

I can get the bike to start and idle poorly with various pilot screw adjustments (mid-range to further in is better) and a lot of adjustment on the idle knob. Idle is rough (almost like a dead cylinder) and the throttle hangs. It will die if you don't hold down the throttle or adjust the idle screw very high.

Previous bike symptoms were bad charging, rotten fuel, rusty gas tank, carbs out of sync, and least of all my worries were the top end performance. It would cruise okay but leaned out on the top end, struggled to run in the top third of the RPM, and needed to be choked every time it was started, even when the engine was hot.

The valve adjustment went according to plan. I don't think anything is amiss inside the engine. I marked the cam chain and gears with paint before rolling the cams out of the way and rolled them back into place, so I can't think of any way the crank would have rotated while the cams were loose. As rough as the engine runs I can hear the valve train clacking away happily with everything set to max clearance.

Here's where I probably went wrong. I changed the carb settings. They worked okay in stock form but the bike has a Mac 4-1 exhaust. Internet wisdom claims that you must rejet to use this exhaust so I lowered the needle clip one notch and went from #92 to #95 mains. Luckily I can still replace the main jets without removing the carbs.

I did not have a manual to set the slide adjustment screws. The slides were removed and I set all the screws at 30mm as measured from the bottom of the throttle arm to the top of the throttle adjustment screw. I don't know proper way to measure this but it was a convenient baseline and easy to measure. How should you measure this for a stock carb tune? What is a good baseline? If they are adjusted too far out does it cause poor idle symptoms? Should I adjust the throttle screws or pilot screws first?

Sorry for being so verbose :blush:

First off, don't be sorry for being to "verbose" for you have provided a lot of information where some of these postings will be so vague, we end up with more questions than answers...

Let's assume for a moment all valve clearances are to spec, camshafts and timings are correct....

"rotten fuel, rusty gas tank, carbs out of sync"
Let's start here, when you had these apart, did you clean and re-build the carb insides for you may have rust particles/gunk build ups?

Are they properly synched now with spec'd vacuum (2cm between the carbs)?

As for jetting for 4-1 exhaust systems... There's truth to this statement, yes for optimum performance but it would have still started as it was. May just run too rich/lean, piss poor idle as in your case, carbonized plugs etc... but should start.

For idle, the pilots is most likely your culprit... How many turns out are you on the pilots now? More than 2 full turns and if your plugs are carbonized, then yes, change for a more leaner jetting on the pilots....

Same time, if too lean, will also run piss poor at idle... Set them to OEM turns out probably somewhere around 1.5 turns out.

In speaking with my two mentors (Plummen and Larry C) for my case (New CR Specials) you DEFINITELY don't want to change all jets at the same time for you will only be chasing the issue all over the place, especially on new motor builds...

Again assuming all top end configurations, settings measurements, intake leaks etc... are to spec...

Basic Rule of thumb, set carbs at OEM spec for the moment for pilot turns out, needle jet clip position, main jet etc... then run the bike out on the hwy or wherever you can really run her at mid to WOT ranges... Don't red line it but do run it at load and don't stay at a constant rpm range, vary it by twisting the throttle.

Get one range working more or less to ideal operations (performance, rich/lean, accelerations, bogging, exhaust popping, spark plug conditions etc...)then go for the other....

As depicted in this diagram... The jets do overlap into the other ranges but for the most part the concepts remain the same for most carbs...

Mains: 3/4 to WOT
Needle: 1/4 to 3/4 throttle
Pilots: Idle to 1/4 throttle

NOTE: These are for my CR specials, your manual should provide something similar....

OMR

Is it a 1983 KZ550 LTD with this oem carb?

Good Luck!

[Click on image to enhance view]



Edit -- this CV carb is shown by kawasaki.com on the 1983 KZ550-M1 LTD with shaft drive.
As later noted, the KZ650 at hand is a 1983 KZ550-C4 LTD shown by kawasaki.com with manual slide carbs and chain drive.

Nope, my 1983 kz550 ltd C4 has TK22 carbs. None of that CV stuff to deal with this time.

The carbs have been cleaned and rebuilt twice in the past year. We are also using a much nicer fuel tank, there is still some fine rust, feels like chalk dust, showing up in the filter but it's nothing at all like it was. They are NOT synchronized yet. I don't have the gauges and wasn't sure if you can even sync the carbs with an engine running so badly. I may be able to borrow a set of vacuum gauges though.

I used WD40 around the intake boots (brand new air box ducts $$) and could not detect a change in engine speed.

What gets me is that last summer after a full rebuild everything plugged right in and ran great. Fired on the first try. The rusty fuel tank ruined that shortly. Once the engine really heated up it would run erratically and the idle speed would fluctuate. I figured that was the valves heating up and losing clearance because some of them were too tight.

I forgot to mention that I also removed the emissions junk from the engine. Carb intake nipples on 1 & 4 are capped, both reed valve covers are sealed off and I filled in the front airbox hole, although I considered leaving it open for extra air flow.

Sometimes there isn't much worse than getting that bank of carbs installed. I hate it. I'll disassemble the carbs and to adjust the jet needles while they're still installed before I do it again. $hit gets old quick!

I have never run a bike with bad cam timing but there is a seed of doubt that I managed to screw up cam installation. The primary chain is making so much noise at bad idle that it scares me. My painted marks lined up perfectly and the crankshaft was never rotated. Is it possible to get the cam timing off any other way?

It's my birthday so I'm going to get another bike running and head into the country, but I'll verify spark and plug condition again before making more changes.

Grebnaws Inc. wrote:

...did not have a manual to set the slide adjustment screws. The slides were removed and I set all the screws at 30mm as measured from the bottom of the throttle arm to the top of the throttle adjustment screw. I don't know proper way to measure this but it was a convenient baseline and easy to measure. How should you measure this for a stock carb tune? What is a good baseline? If they are adjusted too far out does it cause poor idle symptoms? Should I adjust the throttle screws or pilot screws first?....

Is this referring to bench sync where throttle slides are set equal slight distance (say paper clip wire size) from closing against bore?

Good Luck!

No, I didn't use that method... It slipped my mind. I measured the total length of the arm and exposed screw from one of the assembled and untouched slides and just set the others to the same height. Figured it was "good enough" for a run in.

If you have good spark, timing and compression, from what i read i would lean toward the carbs being out of sync. The sync should be roughed in the way Patton describes and then once it is running use vacuum gages to dial it in real nice. This is the way i did my TK carbs and mine runs nice!

Good luck!

Another 2 hours and no luck. My #2 cylinder was cold but spark was good so I removed the float bowl and cleaned out the jets again. They didn't appear clogged but header the pipes seem more evenly heated.

It realllllly don't want to pull the carbs again but I can't seem to adjust anything that will allow the bike to idle without holding the throttle open. I have turned the mix screws in and out at every turn while raising and lowering the throttle slide screws. If I can get it to hold a rough idle then blipping the throttle sends revs soaring and hanging.

At any rate, the idle control knob should be the last thing to adjust, right? How should it be set for the other adjustments?

Your air screws should be about 1 to 1-1/2 turns out. I think you will need to take off the carbs and bench sync them to get them close.

They didn't appear clogged but header the pipes seem more evenly heated.

So does this mean that it is running on all four now?

The TK carbs a fairly simple carb as carbs go. You may need to go back thru them carefully to see if anything is wrong in there.

As Harm said, the TK22's are about as simple as carbs get.

If you adjusted the slides by the upper adjustment screws, you altered the balance on the carbs. You will definitely have to use a vacuum-synchronizer of some type to get them back to balanced. But you need a rough balance to start with. If you don't have a gauge, you can take them off, turn the idle down so the slides are almost closed, and carefully look through the carbs toward some light source. You want to adjust the slides so each carb has the same amount of light coming through under the slide.

If you are off by one turn on the slide adjusment screws (on top of the carbs, not the air screws), the idle will be way off. A good vacuum gauge will get you to within about 1/8 turn.

If you have a gauge, you don't need to take the carbs off to do this adjustment, but you will need a bottle and a long hose for gas because the tank will have to be off.

I took the carbs off again and reinstalled all stock components. #92 mains, #32 pilots, clip on 3rd notch. Bench sync'd with 1mm steel wire, with the throttle stop set so the slides just peeking at the top of the opening. Throttle stop screw is not turned in. The "timing lever" screw was set in the middle of it's range for the bench sync.

I still can't get it to idle. Starting with 1 1/2 turns out I have tried adjusting the mix screws another dozen ways, 1/2-3/4 turn out allows the engine to fire off choke but will not run. With full choke the engine fires straight to life and races to 4000rpm and hangs. The engine dies if you touch the throttle, even just a blip, and will slowly die if you adjust the idle down or engine speed using any of the other controls.

I resorted to turning the timing lever screw in and out but don't know if this is proper procedure. How should that screw be set? It seemed to fire off choke with the screw turned out (slides lower) but the slides were only set to 1mm to begin with. I recorded the setting so I can put it back the way it was at bench sync if necessary.

At this point I'm feeling pretty lost. What else can be adjusted? The base settings don't work. It will only fire and hang at a scary high RPM before dying or on a forced idle using partial choke and the idle screw.

Well well. Here we are again. Don't you hate it when you tear your hair out, pay someone else to do the work, and you get the bike back with all the same problems?

I spent the past month ignoring the bike while trying to sell it. No interest in the bike. Not at any price. We were in the process of moving and I wanted one less thing to worry about when we got moved in. Registration and insurance were due and the bike hadn't been ridden all year. We just wanted it gone.

Well, we got settled in to the new place and with the close of riding season at hand I said there's NO WAY we're selling this bike for pennies on the dollar so I went back to the beginning.

I found exhaust valves 1-2-4 with no clearance. I had just finished adjusting them. The math worked out on all the other valves but these ones weren't having any of it. I removed the cams, checked everything out, crunched the numbers again, put everything back in place, re-torqued the cams, and whaddya know? All the clearances are back in spec. Something must have been off. My guess is that the shims weren't seated properly.

So.... A little tweaking and the bike starts up, idles real high, but doesn't fall flat.

A little more tweaking and it runs great with a slightly high idle of 1400-1500. I can't get the idle any lower no matter how far out I turn the fast idle screw. The idle knob isn't even touching. The mix screws are 1 1/2 turns out.

I still need to see how the cold starts are but I'm back on the right path. Took it for a 3 mile ride and it's as smooth as ever.

It's just about time to get this bike back on the road....