81 KZ550 weird idling and throttle issues

Firstly, I cant seem to get the bike to stay at a nice, smooth, low rev idle without manually adjusting the idle knob on the back of the carbs. But, when I increase the idle speed the throttle "sticks" and the engine remains at a high rev before calming back down to idle...this particular problem is much worse when downshifting on the road and the rev just seems to stay really high.

Setting the idle speed lower seems to remedy the throttle sticking issue, but the bike will stalls a couple seconds after I let off the throttle.

Here's a link to my bike from earlier today

It sounds like your carbs need to be cleaned or you have some vacuum leaks. If the bike is new to you, you should see if the carbs have been jetted to run with the pod filters

Besides the other things mentioned, it also sounds like it may only be running on two cylinders. Do a spit test to see if all four exhaust pipes are getting the same heat. Water should dance on all four pipes. If it's not the same on all four, then some cylinder(s) may not be firing.

loudhvx wrote: Besides the other things mentioned, it also sounds like it may only be running on two cylinders. Do a spit test to see if all four exhaust pipes are getting the same heat. Water should dance on all four pipes. If it's not the same on all four, then some cylinder(s) may not be firing.

So to be clear, I should pour a bit of water near the exhaust headers and watch how the water behaves? I guess I should warm up the engine a bit too right?

@nickleo373 Can I determine if the carbs have been jetted correctly without pulling them out?

Also, I noticed that the vacuum seal(?) or the larger hose that goes directly from the gas tank into the carbs doesnt seem to be clamped or sealed at all...looks like it was just pulled over the opening above the carbs and left that way.

If you had a low profile ratcheting screwdriver it might be possible, but it would probably take less time to do it with the carbs off. Plus if the carbs are off the bike you will be able to see what type of condition the parts are in.

Could also check for vacuum leak at carb boots by spraying carb cleaner on boots , while at idle, & see if there is any change in RPMs

You have pod air filters on CV carbs. Tell us what you did regarding jetting changes. Has it ever run properly with those air filters? Ed

650ed wrote: You have pod air filters on CV carbs. Tell us what you did regarding jetting changes. Has it ever run properly with those air filters? Ed

The previous owner put the pod filters on the bike and I dont think he ever had the bike running properly. He got them for aesthetics, but it seems like he never jetted them properly.

You should first identify what motor you have. That is not the motor from an 81 KZ550A.

It is a second generation KZ550 motor. You can tell by the more angular details on the castings. But there are several different types of second gen motors. The second generation motors use CV carbs with larger boots which are not compatible with the 81 airbox. Also, most later airboxes won't fit into the 81 frame. It may be possible the 83 KZ550A4 airbox might fit, but I'm not sure. It had the later style motor, with the earlier style frame.

If the engine number is KZ550A, then it's likely an 83 KZ550A4 motor.
This is the most likely motor since it doesn't appear you have an oil cooler.

If the engine number is KZ550D, then it's an 82 or 83 gpz motor from a KZ550H1 or H2.
These came with an oil cooler connected at the oil pan.

Both of the above motors came with Teikei TK-26 CV carbs, but with slight variations. Dynojet has a jet kit for running pods on those carbs and it works well, as long as the carbs are in good shape. The main problem with those carbs would probably be the diaphragms. Next would be the rubber/plastic jet caps inside the carbs. When they get old and crack, they leak fuel into the pilot system and cause rough running.

If the motor says KZ550D, it can also be an 84 or 85 ZX550A1 or A2 gpz motor.
That motor would also have had an oil cooler, but would have come with TK-27 CV carbs.
The TK-27 carbs don't have the rubber/plastic plug. There is also a Dynojet kit for them, which may even be the same kit as the TK-26 kit, but I'm not sure. TK-26 carbs and TK-27 carbs can be interchanged relatively easily. The rubber plugs over the pilot system will tell you which carb you have. You can also identify the TK-27 by the remote idle screw which comes out the side of the carb bank.

The gpz motors breathed better so the jetting would be different from the KZ550A motors.

@loudhvx, I really appreciate all the help you and the rest of the guys here have given me.

So it seems like you where right, and my motor is a kz550D and I also think I have the TK-26 carbs. I do have an oil cooler on my bike I didnt take a picture, but it I've attached an image of what it looks like.

and I did not see a remote Idle screw on either side of the carbs. I've added a couple pictures just to make sure I'm on the right track.

If we can confirm that I do have the TK-26 carbs, can you suggest any reputable online retailers I can purchase the jet kit from?

You lucked out, you have an engine from an 82 KZ550H1 or 83 KZ550H2.
They are far more desirable, and hard to find, than the standard KZ550 motor, especially if they are in good shape.
They had red oil coolers and the TK-26 CV carbs.
The idle speed knob will be down low, between the #2 and #3 carbs.

You need to find a way to mount the oil cooler. The gpz engines have higher compression and generate more heat, so you will want the cooler.

Once you clean the carbs and confirm the jet plugs seal properly and the diaphragms are working properly, you can use Dynojet Kit #2107.

www.denniskirk.com/dynojet/stage-1-and-3...71745.prd/171745.sku
Dennis Kirk is out of stock.

You can try:
www.amazon.com/Dynojet-Research-Jet-Kit-Stage/dp/B000GUZ3CE

Beware, there are counterfeit Dynojet kits out there. Their website shows how to spot some of the counterfeit ones.

By the way, don't drill out the slides right away. Some say to try it without drilling first.

I have never installed used this kit myself. I only know of others who have. You may want to get on the Gpz550 forum as well.

Also, check your compression and ignition before spending too much time messing with the carbs.

The oil cooler is already mounted, I've attached a picture of it below. Yep, that's exactly where my idle speed knob is.

So in terms of cleaning the carbs, can I follow this
There are also plenty of videos that I've found on the subject, but none of them relate specifically to the TK-26.

What am I looking for the compression and ignition?