1983 kz550 ltd carb questions

The saga continues...

I removed the carbs for a full rebuild about a year ago and they sat again for half a year without being put away properly. I got the bike out of storage (if you can call it that!) and changed out the charging system. The bike fired up well and carbs worked well enough for sorting out the charging issues but today the bike wouldn't run for crap. Header #4 was stone cold.

I was working away from home and I didn't have all my tools so I removed the float bowls, ran wires through the jets, and sprayed all the circuits without removing the carbs. It was time consuming but not too difficult with a 1/4" thumb driver. Everything was completely plugged with gelled gasoline. Does modern gas really turn to gel in 6 months? Nasty stuff.

It went back together without any problems but I am still sorting out the idle mix screws. From what I can gather, turning the idle mix screws OUT makes them LEAN and turning them IN makes them RICH. So fully seated is fully rich, correct? Exactly what is a full turn on the air mix screws? Is a turn considered 180 degrees or 360? I want to make these adjustments to ease cold starting so even though it was rideable while hot it could be a different story in the morning.

The bike has a MAC 4-1 exhaust with stock jets and airbox. It seems to be running lean, like it's just on the edge of sucking air through the pipe while cruising and will pop when the throttle is snapped shut. The engine revs well but struggles for redline while riding and desperately needs to be sync'd. The carb rebuild kits included needles with adjustable clips, and I believe they are currently set 2nd notch from the top.

Will dropping the clip to a lower level help? If so, can this be done without removing the carbs? I can't remember what it took to disassemble these carbs and would like to avoid breaking them down again.

Will the idle mixture screws also be affected by the 4-1 exhaust? Should the idle mixture screws be set before or after synchronization? I'm also checking the valves before taking the bike to a friend with vacuum gauges.

I rode the bike home and noticed a few things. They are unrelated to carb issues but the kz550ltd seemed to cruise at much higher RPMs than I remember, around 6k at 70mph. It was feeling high strung and the rear felt wobbly. Is 6k typical cruise rpms in 6th gear?

Thanks for the help. I've moved to a newer bike so I'm not forced to deal with these problems every day. The girl and I are both down a car this week and I wanted to put the kz back into service.

Yes, try dropping the clip one notch and see if that helps you lean condition. The idle screws you describe are probably pilot air screws, although I do not know what carburetor you have. Air screws lean the idle and low speed mixture as they are screwed out. One full turn equals 360 degrees. Might suggest that you turn these screws in all the way until they are lightly seated and then back them out one turn and see how it runs.

Robert

Forgot to tell you that my Gpz550 runs approximately 72 mph at 6,000 rpm, but my gearing may be a little different than yours.

Robert

I'm pretty sure these are tk22 carbs.

The tach goes absolutely wild at high RPMS. We have already replaced the speedo and tach cable but the gauges still flutter a bit. I don't think the clutch is slipping but I don't know for sure, but that would possibly explain 6k rpm @70mph. today I adjusted the clutch pushrod and cables and took the bike for a ride with the air mix screws about 1 turn out. The bike starts easily on full choke but took a lot of adjusting and warm-up before it was rideable off choke. As long as it was idling around 1200-1400 it wouldn't die (and there is a 200-300rpm flutter from being out of balance.)

Now I have the valve cover off for valve clearancing. I have done this before with my cb900f but have never done anything with shim under bucket valves. I've got a lot of reading to do before yanking the cams out.

Two things worth noting so. The horn had to be removed for access to the front center cam bolt, and the coils had to be taken off to remove the cam cover. Not a big deal but the horn was kinda lame.

I want to ditch the emissions equipment while it's off. What is a convenient way to plug the reed valve covers, and do I need to plug the big hole left in the front of the airbox?

I have TK22 carburetors on my bike and it does have pilot air screws. Mine are set at 1-1/2 turns out, but I have the stock exhaust. Try turning them in a little bit more and see if it helps. My tachometer and speedometer jump all over the place above 60 mph. Tried to lube the cables, but did not help.

Robert

You can run a hose from one cover to the other and that effectively blocks it off. Yes, you will want to plug the hole in the airbox

The LTD "C" model which is chain-drive has the TK22 carbs. The LTD "M" model has shaft-drive and uses larger TK CV carbs with diaphragms on top.

You can find a gearing/speed calculator in my signature for the 550 bikes. You need to know the sprockets and rear tire circumference (which you can just measure by rolling the bike for a few wheel rotations).

I've made a lot of progress over the past week. Carbs are off the bike for another cleaning, needle clip dropped a notch, and I took measurements for all valve clearances. The fuel filter was also completely clogged with very fine rust. I flushed it out for re-use but will have to find a paper element for more protection. The fuel line became kinked very easily the last time I tried another type of filter so I'll have to experiment.

One intake valve was close to zero-clearance, one .05mm, and the rest were all at the extreme limits. After swapping I only had to order 5 shims from Z1 and picked up a set of keihin #95 main jets should the kz need a bit more fuel for the Mac exhaust. Searching the forum leads me to believe the Mac 4/1 needs lots of fuel. I also replaced the float bowl screws with socket head screws in case I need to change the main jets again without removing the carbs.

Check out the rubber carburetor boots attached to the engine for cracking, unless you have already! It gets a little tedious taking those carburetors on/off so it is good that you can change jets now on the bike. My bike has #94 jets in it.

Robert