idle air screw settings

So after a month and a half of being apart I finally have the 550 back together, before I put the carbs back on I tried to set the idle air screws to the UK standard since there was no setting for the US model. I now have the problem of the bike trying to stall at low RPMs all the time. The setting I changed it to was a full turn more out than I had previously set them. So I'm wondering what the setting should be.

nosbearatu wrote:

...idle air screws...full turn more out than I had previously set them. So I'm wondering what the setting should be.

Side located pilot air adjustment screws allow more air into the mixture as they are screwed out. The needle pointed end governs the amount of air allowed from an air passage into fuel mixture at the pilot jet.

If this is your situation, they are likely too lean. Just guessing, I would say begin at 1 and 1/4 turn out from lightly seated and adjust idle from there. But perhaps someone else will offer a better starting position for your particular application.

Patton has it just about right. The 1981 550A2 is the same as the 1980 A1 for the U.S.

I've compiled some info on TK carbs for the early 550's (and 400/4 and 500/4)

All TK 22 carbs are same except main jets and needles.
The number after the dash in the needle number represents the clip position from the top (out of 5).
The 4D92 needle is the same as the 4D93 needle set at clip position 2 from the top (out of 5).
Canadian 550 models use the 4D93 adjustable needles.

Supposedly, slides with different cutaways exist, maybe for racing, but all of the KZ400, KZ500, and KZ550 with TK-21 or TK-22 carbs used the same slides.

The USA models have plugs over their air-screw openings, so the air-screw setting is in parenthesis since they are not officially accessible. The KZ550D model carbs are also painted black.

This chart represents the models using TK21 or TK22 manual-slide carbs. Later models with CV type carbs are not represented here.
The same bikes, made in subsequent years, using the same carbs most likely have the same internal setups. For example, the 1981 KZ550C2 and 1982 KZ550C3 would have the same setup as the 1980 KZ550C1, because they also use the TK22 carbs. However, the 1983 KZ550A4 uses different carbs than the 1980 KZ550A1, so its setup would have to be different.

Note: All models with TK21 and TK22 carbs have the same pilot jet, slide, and fuel levels.

The West German 550 model is puzzling since it is listed as haveing the smaller carb, yet the 500 has the larger carb. Maybe it's a typo in the FSM.

K&L rebuild kit 18-2462 comes with Y77 needle which is same as the 4D93 needle and second clip from top matches the 4D92 needle.

Since they are indeed air-screws on the TK22 carbs, turning-out leans the mixture. Turning-in richens the mixture. If everything is stock (exhaust and intake and motor), the stock settings should be almost right on. If not, look for other problems. If the airbox is off, you will most likely have to go richer. If you have an aftermarket exhaust (especially with a Mac) you will need to go richer. With a Mac, you may even have to drill the pilot jets to 35 or even 37.

Post edited by: loudhvx, at: 2007/10/12 12:06

ok, thats about what I had it set at before, the uk setting in the clymer manual was 2 3/8 turns. I'm just going to change it back then, thanks.

I added some notes to the post above.

Also, check this mod out for the choke. I designed it. It's very simple and really helped with starting and choke-warm-ups.
www.geocities.com/loudgpz/GPZchokeScrewMod.html

Also, very carefully inspect the choke flaps. The pivot shafts can walk out which causes the flaps to not seal properly. I find I have to re-install the shafts and peen them ever-so-gently because the choke plates are brittle castings.

It really pays dividends to get the choke plates and assembly working perfectly.

Post edited by: loudhvx, at: 2007/10/12 12:03

Yeah, that choke mod probably wont have much effect on my carbs as I discovered that the previous owner had not taken care of the carbs and two of those little flaps on the choke slides are missing. Here is hoping they aren't rattling around in the engine somewhere.