kz550 '81 only starts with choke OFF and idles really high. New carb kit.

Picked up an ‘81 kz550 Ltd which was not running due to 'dead battery and fuel running out through carb overflow tubes'. The owner said it worked previously, rode from MN to CA on it. It has stock exhaust.

Previous owner put on pods. I fixed the valve clearances (not off by much), bought new pods, and cleaned/rebuilt the carbs with a kit (see attached pic of the kits) . When I worked over the carbs I noticed the bike had stock jets or at least had they been drilled I could't tell. Being that the new kit had stock jets, and as suggested by others, I moved the needle down one position as a first attempt before drilling jets. I checked fuel level with clear tube method and that seems fine.

The bike will turn over but only starts with choke OFF! If I blip the gas it hangs at that rpm. If I try to start with choke on it revs crazy high and I have to shut it down in one second!

What am I doing wrong? Been reading the previous posts but I’m still lost. Thanks!

Can't see any photo of jet kit. Did you get a Dynojet kit?

The high idle is most likely a vacuum leak from aged carb boots.

Thanks Nessism. So it's a lean situation? I'll try spraying the boots to look for a leak.

I forgot to mention that I disconnected two tubes on the carbs - they were connected to larger tubes which were connected to the top of the valve covers. The holes on top of the valve covers where the large tubes connected were plugged. I assumed it was a 'pollution thing' so I removed the large tubes and plugged the smaller air hoses connected to the carbs. Would that have any effect? I can take a pic if needed.

It was a K&L carb kit. I attached the image again, fingers crossed.

If it starts cold with no choke, it's not lean. Kz550's are all pretty cold blooded and need choke to start on most days.

Still can't see any photos.
You can use a drill set to measure the jets to see if they are drilled or not. The TK22 site has details on that too.
The K&L kits I've bought had what looked to be factory parts, so unless they changed, they should be good, but the rebuild kits have stock jets for a stock airbox.
The only adjustable part would be the needle.

s3.amazonaws.com/gpzweb/TK22mainPage/TK22mainPage.html

What needle setting did you use? Which clip from the top?
If it's rich enough to start with no choke, it will usually be too rich when warmed up.

The choke has a throttle position adjustment. It opens the throttle when you turn on the choke. It needs to be adjusted carefully to prevent the racing idle.
Here is a modification that allows you to adjust it on the fly:
s3.amazonaws.com/gpzweb/TK22mainPage/TK2...astIdleScrewMod.html

Thanks for your help loudhvx!

I have it running but now as I’m trying to sync the carbs I have an issue where I can balance the carbs at 1000rpm but the gauges read 12 in. Manual says should be 7.5-9.5 in. Is there a way to lower/raise the overall in? Does this higher reading indicate anything important?

kz550oak wrote:
Does this higher reading indicate anything important?

No, it´s more important that all gauges readings should be equal for good carb sync.



And you have to check the gauges calibration first.

kz550oak wrote: Thanks for your help loudhvx!

I have it running but now as I’m trying to sync the carbs I have an issue where I can balance the carbs at 1000rpm but the gauges read 12 in. Manual says should be 7.5-9.5 in. Is there a way to lower/raise the overall in? Does this higher reading indicate anything important?

I don't think 12in. is correct. The factory manual says 19 to 24 cm (with airbox). That's 7.5in. to 9.5in.

The vacuum with airbox is not much different with pods.

With pods on a Gpz550 and Tk22 carbs, I think I normally see from 160mm to 250mm Hg at idle or with a slightly fast idle. That is 6 inch to 10 inch, very roughly. Probably closer to 220mm (8.7 inch) most of the time.

I have quite a few manuals regarding the 81 Kz550's. Please download all of them. Some have updates over others.
s3.amazonaws.com/gpzweb/Mnls/Mnls.html

Thanks for the help. I got the carbs to sync at 12. I do use the choke to get it started but after a minute I shut the choke off. It seems to run fine. I made/installed new choke flaps as others had suggested.

Do I need to use the vacuum for the petcock on this bike or can I disengage the vacuum, plug the ports, and run on PRI? Any benefit to using the vacuum? Not having any issues currently, just curious.

I took it for its first spin yesterday. It's a great bike! I'm happy with the way it's coming along. Seems to be running well enough but I haven't tested it extensively enough yet.

kz550oak wrote: Thanks for the help. I got the carbs to sync at 12. I do use the choke to get it started but after a minute I shut the choke off. It seems to run fine. I made/installed new choke flaps as others had suggested.

Do I need to use the vacuum for the petcock on this bike or can I disengage the vacuum, plug the ports, and run on PRI? Any benefit to using the vacuum? Not having any issues currently, just curious.

I took it for its first spin yesterday. It's a great bike! I'm happy with the way it's coming along. Seems to be running well enough but I haven't tested it extensively enough yet.

The benefit is that the bike won't empty the tank onto the ground if your float sticks or overflow cracks, and it may disable the reserve capability. No reason to want to run on prime.

When the petcock is working as it should, there are benefits to running on "on". It automatically shuts off when the engine stops. That's the big benefit as OldJeep detailed in his post. And running on prime could get you stranded since you will already be on reserve all the time.