KZ 550 Carb Woes

Hi crew, first time long time, etc.

So I have an '83 KZ 550 LTD (550C), 13K, which generally runs like a champ. For the last year I've been having some carb issues (stuck float causing fuel overflow, backfiring, etc) so like a genius this week I decided to clean and rebuild the carbs.

I did so as carefully as I could. I didn't separate the carbs, soaked them in cleaning solution, replaced o rings and brass bits very carefully, blew out all the passageways with an air compressor, and took careful notes and photos to put everything back as it was (as near as I can tell). It reassembled easily and everything moved as it should. Much cleaner, as would be expected.

Now, after I got everything back in and buttoned up, the bike will start, and idle at 1100rpm, with the choke all the way out. But if I so much as touch the throttle, it bogs and stalls. Likewise, if I move the choke in even a little, it dies.

I have the air mixture screws set at 1 1/2 turns out (per manual) and have experimented with them in lots of different settings, with no significant results. I also pulled the air filter just to see if running it artificially lean would make a difference, and it didn't.

My manual tells me that from 0 to 1/8 throttle involves the pilot system, so I'm guessing something is wrong there. Just to clarify, the pilot jet screws (the screws accessed by removing the float bowl) should be snug, right?

Any other ideas as to where I might start looking?

Thanks in advance.

I'm a little confused by your choke comment. The Kz550C models had TK22 carbs which have a choke lever that moves up and down to rotate a shaft. If your choke is a knob and moves in and out, then it may be a different bike (or possibly a different motor).

The link in my signature wil lead you to a TK22 website. You can confirm the TK22 carbs are what you have by comparing the photos on that site. If they are the same, I have manuals for your bike in case you need them. the links are on the link page from my signature.

Are you using the stock airbox and filter? If not you will have to rejet the carbs.

I'm not a fan of using aftermarket carb bits inside the OEM carbs since the parts are typically of inferior quality. You also can not perform a proper rebuild unless you ungang the carbs and clean everything properly and replace all the various O-rings.

Ivan42 wrote: Hi crew, first time long time, etc.

... replaced o rings and brass bits .....

Why? Had someone damaged the brass bits? Ed

Ivan42 wrote: . . . '83 KZ 550 LTD (550C) . . . carb issues . . . soaked them in cleaning solution . . . blew out all the passageways with an air compressor . . . bike will start, and idle at 1100rpm, with the choke all the way out. But if I so much as touch the throttle, it bogs and stalls. Likewise, if I move the choke in even a little, it dies.

I have the air mixture screws set at 1 1/2 turns out (per manual) and have experimented with them in lots of different settings, with no significant results. I also pulled the air filter just to see if running it artificially lean would make a difference, and it didn't.

My manual tells me that from 0 to 1/8 throttle involves the pilot system, so I'm guessing something is wrong there. Just to clarify, the pilot jet screws (the screws accessed by removing the float bowl) should be snug, right? . . . .

pilot jet screws (the screws accessed by removing the float bowl) should be snug, right? --- correct, should be snug.

Would suspect that pilot circuits aren't yet "as-new" clean.

Would speculate that the orifices into the carb bore (where the pilot circuit mixture exits) might be clogged. As this is a condition that may exist absent actually seeing carb cleaner sprayed through the pilot circuit exiting into the carb bore.

Good Fortune!

As mentioned, you should not soak the carbs if you did not separate them. If you did not separate them, you could not remove all of the rubber parts.

The TK22 carbs (if that's what you have) rarely need to be separated. Their fuel rails and associated connection parts are almost never a problem. But this means they should also not be soaked. They are such simple carbs, a can of gumout with a straw will usually clean what's needed.

Now that they've been soaked, keep an eye out for possible fuel leaks in the fuel rail.

And, also, as mentioned, there are some no-name rebuild kits out there that have bad parts, like the metering needles. Also, the replacement fuel valves are usually a different height from stock, so if you replaced them, you may need to reset the fuel level per the manual. The Tk22 site has some additional details not mentioned in the manual.

I've got a little hobby going of rebuilding and spiffing up old carb sets and then flipping them on ebay for profit. Of all the sets I've done in the last few years about three quarters of those sets have had hard and brittle O-rings on the fuel transfer tubes, which distribute fuel to the various carbs from the central fuel Tee. And the only way to upgrade these O-rings is to ungang the carbs.

Everyone is free to do what they want but to me it's just plain dumb to go through all the trouble of cleaning carbs and not doing the job right. I'd venture to guess that the success rate of people rebuilding carbs is less than 50% too, partly because they shortcut the process and do a half assed job.

Well, maybe I've just been lucky, but even the really worn out, dirty carbs I got off ebay didn't need to be deganged, and they've been working fine for 10 years. I own about 6 sets, and have worked on dozens. The TK22's are a pain to degang, and I've seen many get damaged in the process... bent throttle shaft or bent choke shaft, stripped screws etc. If the shafts are rusty, they need to be cleaned before disassembly or they can get stuck.

As a side note, the rebuild kits don't supply orings for the fuel rail (double oring on every connection ).

They can always be deganged later without having to re-open them, if the fuel rail is leaking.

I'm only talking about the TK22's, though, and assume the OP may have them. I've seen many more posts about other carb brands with leaking fuel rails etc. Obviously, they need to come apart.

Nessism wrote: Everyone is free to do what they want but to me it's just plain dumb to go through all the trouble of cleaning carbs and not doing the job right. I'd venture to guess that the success rate of people rebuilding carbs is less than 50% too, partly because they shortcut the process and do a half assed job.

What he said.

OK, thanks fellas.

To clarify a few questions - these are the TK22's, and the motor will only idle when the choke is "up" (not "out" as I originally said). The choke needs to be in the fully horizontal position. Also, it's the stock airbox and filter.

Sounds like I screwed up a few things in my approach. I don't mind that, I learn best by taking these things apart 10 times. Maybe I can remedy my errors...

1. I Shouldn't have soaked the carbs without separating them. I didn't separate the carbs because I had read here and otherwise that it was a PIA, and that it rarely resolved problems. But by soaking without deganging I may have damaged the o-rings in the fuel rail. How would I know that? Leaking fuel, right? So far, no leaks that I can determine, so maybe I got lucky.

2. I Shouldn't have replaced the OEM brass parts (pilot screw, needle etc) with those from the rebuild kit. The OEM ones I replaced didn't appear to be damaged in any way, I just assumed that the rebuild versions were there for a reason, and were shiny and new, so I put 'em in.

So my plan now is to remove the carbs, inspect/clean the OEM brass parts and use them to replace the aftermarket ones I put in, check the fuel levels in the bowls, check that the pilot circuits are clean (via Patton's approach) and reinstall.

anything else I should think about while I've got them out?

thanks again.

Check your fuel level before you remove the carbs, also ensure the throttle cable(s) are correctly adjusted and the slides are all seated when throttle is closed.

Then clean again with an aerosol carb cleaner using the straw to blast the tiny passages that make the idle circuit which are the first to block up,

Ivan42 wrote: these are the TK22's, and the motor will only idle when the choke is "up" (not "out" as I originally said). The choke needs to be in the fully horizontal position. Also, it's the stock airbox and filter.

Ok. Choke up, horizontal, (fully counter-clockwise) is fully choked. Normally, depending on outside temperature, and idle-speed while choked, the motor should run without choke after about 10 to 20 minutes idling. If it's really warm outside, like 90 deg F, you might come off choke in as little as 1 minute idling, that's if it even needs choke to start.

The TK22 carbs have a fast-idle setting while on choke. There is a cam that opens the throttle, which bypasses the normal idle setting. If your idle setting is set too low, the fast-idle setting will let it run on choke, but removing choke will cause it to die because the normal idle set-screw is set too low.

So first make sure the idle set screw is set to open the throttle at least a little.

Ivan42 wrote: 1. I Shouldn't have soaked the carbs without separating them. I didn't separate the carbs because I had read here and otherwise that it was a PIA, and that it rarely resolved problems. But by soaking without deganging I may have damaged the o-rings in the fuel rail. How would I know that? Leaking fuel, right? So far, no leaks that I can determine, so maybe I got lucky.

Yes, the only symptom would be fuel leaking from the fuel rails. That can be fixed later if need be. But As I mentioned, you will want to clean the throttle shaft and choke shaft before trying to separate the carbs. I'm not sure if you can get the throttle shaft dust boots anymore. If not, then you will want to be very careful not to mess those up. I don't have the o-ring size handy.

Ivan42 wrote: 2. I Shouldn't have replaced the OEM brass parts (pilot screw, needle etc) with those from the rebuild kit. The OEM ones I replaced didn't appear to be damaged in any way, I just assumed that the rebuild versions were there for a reason, and were shiny and new, so I put 'em in.

This depends on which kits you bought. Some older kits contain the original Teikei factory parts. Some later, no-name kits have inferior metering needles that really can't be used. But the symptom with the bad needles is too-rich. You are running only able to run on choke, so that is not the problem. I think aftermarket jets should have been ok. They may look slightly different but I *think* they work, from what I remember.

Here is a link on how to identify the more common rebuild kits, scroll down to the fake kit to see if that's what you got:
gpzweb.s3-website-us-east-1.amazonaws.co...TK22rebuildKits.html

Here is a link on how to identify the bad needles. They have no stamping on them, but you can check their taper easily, without special tools:
gpzweb.s3-website-us-east-1.amazonaws.co...K22threeNeedles.html

Obviously, don't throw away carb parts ever. There is always a chance you or someone else may need them in the future, and they take so little space. Even if you go back to your old jets, keep the new ones. Drilling the pilots is the only way to get different sizes, that I know of... but I should search that again in case some new source may have become available.

Ivan42 wrote: So my plan now is to remove the carbs, inspect/clean the OEM brass parts and use them to replace the aftermarket ones I put in, check the fuel levels in the bowls, check that the pilot circuits are clean (via Patton's approach) and reinstall.

anything else I should think about while I've got them out?

thanks again.

Like Tyrell said, check the fuel level with the clear tube method before removing the carbs. This will let you know where you are starting at.

The fuel level needs to be checked while the carbs are perfectly level side-to-side, and angled very slightly forward as they would be mounted in the bike. So you will want to check the fuel level multiple times, with an auxiliary gasoline can, before re-installing.

New fuel valves are often a different height from the factory parts. This link will get you a dry starting point if already removed them:
gpzweb.s3-website-us-east-1.amazonaws.co...stmentsAndMaint.html

Also, make sure your needles are set with the clip in the second groove from the top, or just use your original needles.

This link shows the port routing of the carb body, so you can check them with a spray can (as Tyrell mentioned) to make sure the ports are clean. Wear safety goggles for this! The spray can come out unexepctedly at your face. Avoid spraying the fuel rail, as that will probably not do any good.

gpzweb.s3-website-us-east-1.amazonaws.co...TK22portRouting.html

The choke flaps are easy to check when the carbs are off so you may want to get a good look at those. Here's what to look for:
gpzweb.s3-website-us-east-1.amazonaws.co...chokePlateFlaps.html

Make sure the air-screws are set to about 1-1/4 turns out.

Make sure the slides all show the same size crescent light through them when you look through the carb bore from the engine side. That is the shape of the light that comes through when the slides are slightly open. This is adjusted by the idle-speed knob., but if they are uneven, you will need to adjust the throttle slides individually. If they are close to the same, you will fine tune them when you sync the carbs.

Here's a link for how to change the needles, but you probably already know how to do this:
gpzweb.s3-website-us-east-1.amazonaws.co.../TK22needleSwap.html