83kz550 stall at idle after blipping throttle

Hey all! Got my project bike rebuilt and fired up and broken in. Still have a lot to do cosmetic wise, but seems to be a strong runner.


Starts very easily with choke from cold. Maybe 10-15 seconds and she will idle fine from then out. Runs smooth and without any hesitation or stuttering throughout the rpm range. I checked plugs at WOT, idle and at easy cruising speeds and all looks pretty well. Not the tan color I would like, but close. Its just a little on the lean side during cruising speeds.

To fix that, I though I would move the needle up one clip/washer (not sure what I have in mine).

The odd ball issue is the random stall if I blip the throttle, after its warmed up.

As it is, I can ride however for however long and come to a stop no problem. It happens repeatably when I blip the throttle after coming to a stop, OR when on-off-on throttle at low rpms, i.e. in que at a stop sign or stop.

Air screws are 1.5 turns out from light seat.

Thoughts?

Don't blip the throttle.



Many such problems stem from clogged pilot circuits. They can be difficult and tedious to clear. Just spraying some carb cleaner in a can through them will rarely do the trick. Complete disassembly, long soak in serious, dedicated carb cleaner, compressed air and a small E string from an electric guitar will usually clear them. After that, check by sticking the straw from your canned carb cleaner into the pilot jet hole in the bowl area, and look for even spray into the carb bore. Do not point it at your face, and be sure to wear eye protection.
I suppose it could also be the result of a sticking needle valve or a seriously out of spec fuel level in one or more carbs.
Have the carbs been worked on, disturbed, or changed in any way recently? Do you know if it ever ran well in the current configuration?

Are the carb boots soft and not hard and brittle? Old carb boots can cause air leaks and idle Problems.

Thanks for the quick replies!

The carb boots from the airbox are soft, as are the intake boots. I have not sprayed carb cleaner around them yet to check for air leaks, but the idle is steady under normal riding and stopping. It only stalls randomly when Im inching along. Usually give it a bit of throttle and then roll for a bit, give a bit of throttle and roll, etc. Usual stop and go stuff or waiting to get to the front of a stop sign. Otherwise, all is well. No off idle hesitation or anything.


As far as history or the bike... lol. It came in several boxes, with things dangling off of it. Wires unplugged and that which was attached was loosely hand tightened. The carbs, however, seemed to be in excellent condition. I fully broke them down (not separating them) and checked all the usuals. Pilot and all other circuits were clear. Really was nothing of note dirt/debris wise that I saw. Actually quite shocked as I have pulled and cleaned many, many, many carbs over the years.

lol at the wear eye protection. Learned that one many years ago also. ha

Moving the needle a full clip position is a pretty drastic change on the TK22 carbs. Blipping the throttle quickly creates a very momentary rich condition. Rolling the throttle slowly results in a leaner situation. The fact that you raised the needle and are only stalling on a throttle blip means you might be too rich. Put the clip back and try a thin shim if you can. Really, with the airbox and stock exhaust, you really shouldn't have to alter the jetting at all. The factory needle was not adjustable in the U.S.. If you do get an adjustable version of the factory needle, then the stock position would be the second clip from the top.

If you used no-name rebuild kits in plain white boxes, they could be defective. The needles are too skinny and won't really work at all.

Here's a link showing the defective rebuild kits:
s3.amazonaws.com/gpzweb/TK22mainPage/TK2...TK22rebuildKits.html

This link shows how to properly shim a TK22 needle so the needle won't scrape against the needle jet.
s3.amazonaws.com/gpzweb/TK22mainPage/TK2...shimmingNeedles.html
In my signature you will find a bunch of other Kz550 stuff.

Excellent info! Thank you!

I have not changed anything in the carb. It does look like the carb had been cleaned and possibly rebuilt when I got the bike. Jets look new and clean. The baffles were removed and the airbox is stock.

It really runs great everywhere and the idle is fine currently. Its just that occasional stall in stop and go traffic. Would that be something I may be able to clean up with minor air screw adjustments? I dont just sit at red lights and rev the motor up. But a stall in stop and go traffic, could be a safety issue.

Okay, I misread your first post. When you said you thought of moving the needle, I read that to mean you did.

If the exhaust baffles are removed, then the bike may be a tad leaner than stock but nothing needs to be done. It should still run normal after its warmed up.

I dont think the blip stall is carb related then.

Have you ridden it fast on a highway yet? If so did it stall right after exiting the highway? Then you should check the valve lash. Read the warning in my signature first!

You will also want to do a compression test and verify the ignition timing with a timing light. Maybe the advancer is sticking a bit... Though I doubt it.

I have not had it on the highway for an extended run yet, but I have had it at highway speeds for short periods on vacant back roads. Never had an issue with stalling even if I went from WOT and then chopped the throttle and held the clutch lever in. Went straight back to a normal steady idle. Actually idles better than my FI 2016 Africa Twin. lol

Its kind of hard to describe when it dies. Best way is that you are in really slow traffic where you are lightly dragging the back brake to keep you inching along. Then the car in front accelerates, so you roll on the throttle just a bit and then close the throttle and pull in the clutch lever to slowly coast down. Most often, a couple or three of these routines in a row and when I pull in the clutch, it dies. Starts back up easily enough, though I usually have to crack the throttle open a hair when I hit the starter to get it to fire.

Is it consistent, as in, can you pretty much always make the stall happen?

If so, you could start to rule out some things.

If it was my bike I would want to eliminate the wiring as a possible issue. Pretty much every 30 to 40 year old bike I've come across had a wiring issue somewhere.

As a test, you could run a temporary jumper from the battery's positive terminal to the positive connections on the coil. This will also permanently power up the ignition. (Essentially this is how to hot-wire the bike.) You will need a female spade terminal with a piggy-back male spade (most parts stores have them). This will allow you to install the jumper and still attach the stock wiring at the coil.

Then start the bike normally. To verify the jumper is working, you can turn the kill switch to "off" and the bike should keep running. Turn the kill switch back on and try riding it and see if it stalls. If it doesn't, then you probably have a wiring bug somewhere in the ignition/power circuits.

You might also want to do the same thing with the ground connection from the igniter to the battery's negative terminal.

Excellent! A great place to start. Thank you