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Bike dies with throttle/ Carb tuning help 09 Nov 2019 20:21 #813768

  • kz550ohno
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Hello all!

I'm working with a 1982 KZ550 LTD. At this current time, the bike will start strong with choke but requires throttle to stay alive. With the bike warmed up and the choke off, the idle sounds pretty good but as soon as I add throttle the engine sputters and dies. With the choke ALL the way up the bike will almost die instantly (from my understanding it's supposed to do that). If needed, I can post videos of the bike running.

For some background, after I took the bike into a mechanic they fixed a vacuum leak and told me that my far right cylinder is running extremely rich and the spark plug isn't firing. After riding the bike home from the shop I looked at the spark plug for that cylinder and he was right, it was pitch black. So I opened the carburetors and adjusted the float in the corresponding cylinder to not allow as much fuel into the cylinder. I also changed all of the spark plugs.

The cylinder I was referring to was running rich with the float in the carburetor at spec height. It might also be helpful to know that in addition to that one spark plug that was pitch black, another one was extremely white (running lean in that cylinder). I suspect the bike is running lean now but at this point I'm not sure exactly how to tune this carb to get the bike to run properly. The bike seems to be all out of whack and after attempting to tune it with the owners manual the bike was still running strange.

Other notes:
The air filter is practically new.
Fuel lines aren't clogged.
Petcock works just fine.
New battery.
Looking inside the cylinders there was a lot of carbon but I don't think that has any large affect with the issue I am facing.

I really have faith that this bike can run well but frankly I'm pretty new to this. I hear that carbs are considered really nice to work on, but right now I hate them lol. Please enlighten me and if you have any advice it would be much appreciated.

Thanks!

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Bike dies with throttle/ Carb tuning help 10 Nov 2019 06:38 #813774

  • TexasKZ
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There are several possible causes for what you describe. The carbs are likely dirty and gummed up, the ignition may be in need of attention, and the valves are likely out of adjustment.

The carbs should probably be completely disassembled and very carefully cleaned. All of the soft parts, orings and gaskets, should be replaced. After being bench synchronized, the clear tube method should be used to determine proper fuel level. Then reinstall them for a proper final synchronization.
You will also want to perform all the routine maintenance listed in the factory shop manual. Most of these old bikes have been sorely neglected in that area. Also be sure the valves get adjusted before trying to synchronize and tune the carbs, or you will be doing it all twice.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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Bike dies with throttle/ Carb tuning help 10 Nov 2019 07:14 #813780

  • loudhvx
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Is this bike new to you? Did it ever run correctly so you know what it should run like, or is this possibly your first inline four?

The reason I ask is that many first time inline-four owners are not exactly sure what to expect, so when I work on their bike, it will be way out of whack, as you said. By that I mean it will only be running on two cylinders and those two will be way out of sync, and sometimes it will actually be made to idle on the main circuit (instead of the idle circuit), but the owner just thought it needed a minor tweak or two.

To expand on what Texas Kz said...

So if this bike is new to you, you need to do a compression test with a good tester. Not a harbor freight tester. They often read way incorrectly. The compression should read near 180 psi. I've never seen a 550 read much lower than that regardless of miles or condition.

If this is your first bike ever, a valve adjustment will be tricky. Normally I would say it needs to be checked and adjusted as TexasKz said, but for now, we want to avoid putting in any more bugs, and it will usually run ok as long as it doesn't get too hot if the valves are just out of spec. If you do open the valve cover, read the valve train warning in my signature to prevent doing damage.
s3.amazonaws.com/gpzweb/CamsKZZXZR550500...KZZXZR550500400.html

Next is to confirm ignition. I suspect you are probably having ignition and carb issues. Carb issues are the most complicated, so it's better to take care of the easy stuff first.

A first test would be a water spray test on the exhaust. Get a squirt bottle with water, an actual toy squirt gun works best, probably. When the bike is cold, start it up and use the bottle to test each header to see which ones get hot right away, and which ones only get warm. The water should dance on the metal without really getting the metal "wet". That will tell you which cylinders are getting combustion. You know you are getting spark on at least those cylinders.

To check for actual spark, take out all four plugs (this should be done on the compression test as well, so it's a good time to do both), connect them to the wires, and make sure all four plug bodies rest in contact with the engine. Crank the engine over and confirm you have spark on all four. It's much easier to do this in a garage or at night.

Make sure the advancer mechanism is free to move and snaps back easily. That will cause strange running if it doesn't move freely. To confirm the advance timing, you will need a timing light.

Most of these test are described in the manual. Here's a link to several. You should probably grab all of them while they are available.
s3.amazonaws.com/gpzweb/Mnls/Mnls.html

Here's a link to a site about your carbs. It's not meant as a substitute for the manual, it's for details not covered in the manual.
s3.amazonaws.com/gpzweb/TK22mainPage/TK22mainPage.html

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Last edit: by loudhvx.

Bike dies with throttle/ Carb tuning help 12 Nov 2019 11:14 #813914

  • kz550ohno
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This is my first inline-four. When I bought the bike the far-right cylinder was having the same issue and the exhaust wasn't getting hot. I guess I'm not really sure what it should run like. I took it to a shop and they supposedly did some troubleshooting on it but they didn't give me any compression test results or anything, which I feel they definitely should have with how much money I paid. Oh well.

I'll be working on it this coming weekend again and I'll do the tests you described. I think it is a good idea for me not to mess with the valves just yet. If I have any questions I'll be sure to ask!

Thanks!

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Bike dies with throttle/ Carb tuning help 13 Nov 2019 11:21 #813953

  • Rick H.
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Hey Ohno: You stated that you took it to a repair shop and they did some "troubleshooting". Do you know what they actually accomplished? Did they check/set valves and or timing? Did they install new plugs or anything? It sounds like they must have charged you a substantial amount so they should have done something to help you out or correct the problem. I am not at all familiar with the KZ550's, just the 900/1000's and there are a few differences in procedures. I think I can honestly say valve adjustment is at the top of the list or close to the top, as an initial step because almost everything is based off proper valve adjustments. After that would be setting the timing, but it's quite difficult to set timing first if the valve adjustment is out of whack. There are a lot of individuals on this forum that know much more about the model bike you have and they will give you loads of helpful hints. You said you followed the "owners manual" for carb adjustment, did you mean service manual? If you don't have the service manual for your make/model bike by all means pick one up. I have three for my KZ-1000, but only use two of them. Good luck with your project!
Rick H.
Rick H.

1977 Kawasaki KZ-1000A1

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Bike dies with throttle/ Carb tuning help 13 Nov 2019 11:28 #813954

  • 650ed
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Wow! I can't even imagine taking my KZ to a shop to have them work on it. I'll bet they don't even have the Kawasaki Service Manual much less any in depth knowledge of how old bikes are to be tuned, etc. . Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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