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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 17:44 #830493

  • bmanc2000
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I should really start by saying I'm very new to working on engines, but I have learned a lot thanks to this community! Anyway, I picked up a 1981 KZ440 about a week and a half ago and went on a whole journey of fixing the ignition system and timing (thanks F64!)

Like the title says, the bike will burp and kick to life when starter fluid is sprayed down the throttle body and will keep running if it's kept above 3000 rpm, but below that it wants to stall out and refuses to start without starter fluid. I've already taken the carbs off and cleaned out the three jets in each, I've made sure fuel is making it into the bowls, and I've already tried setting the pilot adjust screw (whatever its name is), and none of that so far has worked.

My assessment, taken with a grain of salt because like I said I'm new to this, is that the main jet and mixture is working fine, as the bike is happy to be above 3k rpm, but I think the issue is in the pilot jet/associated mixture.

Any ideas?

- Ben

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Last edit: by bmanc2000.

[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 18:11 #830495

  • 650ed
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I've never seen a KZ throttle body. Got pics? Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 18:24 #830498

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I would, but I've had the carbs off twice today and I don't much feel like taking them of again, lol. Here's a pic of the side of the bike, the black box to the left is the air filter housing.
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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 19:04 #830503

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Ok. I think there's a terminology issue. You use the term "throttle body" but there is no throttle body on the bike. So where are you spraying the starter fluid? Ed

1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 19:13 #830504

  • Nebr_Rex
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650ed wrote: I've never seen a KZ throttle body. Got pics? Ed


Oh I bet you have.

1980 KZ1000 Classic for starters.
Also the GPz750 turbo and GPz1100 which are sport version of the Z series and have been discussed many times on this board.


.
2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


.

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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 19:48 #830508

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Nebr_Rex wrote:

650ed wrote: I've never seen a KZ throttle body. Got pics? Ed


Oh I bet you have.

1980 KZ1000 Classic for starters.
Also the GPz750 turbo and GPz1100 which are sport version of the Z series and have been discussed many times on this board.

.

I stand corrected. I should have said I've never seen a KZ440 throttle body. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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Last edit: by 650ed.

[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 20:34 #830511

  • bmanc2000
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Apologies for the confusion, I've been spraying starter fluid right into the air intake, right behind where the air filter sits

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[KZ440] Bike has trouble starting and stalls below 3k rpm 12 Jul 2020 21:37 #830517

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650ed wrote:

Nebr_Rex wrote:

650ed wrote: I've never seen a KZ throttle body. Got pics? Ed


Oh I bet you have.

1980 KZ1000 Classic for starters.
Also the GPz750 turbo and GPz1100 which are sport version of the Z series and have been discussed many times on this board.

.

I stand corrected. I should have said I've never seen a KZ440 throttle body . Ed


Now you have.


2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


.
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[KZ440] Bike has trouble starting and stalls below 3k rpm 13 Jul 2020 08:35 #830546

  • F64
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Ben,
Did you soak the carburetor bodies in a cleaner?
The passages inside the body may be clogged.
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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[KZ440] Bike has trouble starting and stalls below 3k rpm 13 Jul 2020 09:18 #830555

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I did not, I only have spray solution and I'm not quite brave enough to take everything apart, diaphrams and all.

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[KZ440] Bike has trouble starting and stalls below 3k rpm 13 Jul 2020 09:58 #830560

  • F64
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You could do it. We all had to start somewhere.
Just take your time.. Take plenty of pictures with your phone as take the carbs apart.
You don't have to separate the carbs.
You're basically taking apart the top and bottom of each carb and cleaning the bodies.

Do you have the factory service manual?


81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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Last edit: by F64.

[KZ440] Bike has trouble starting and stalls below 3k rpm 13 Jul 2020 10:13 #830563

  • gavroyer
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The CV34s are pretty easy to disassemble. Do one side at a time so that if you get stuck somewhere, you have a reference to put them back together. Also, make sure you download the service manual from the articles link above. Also, as F64 noted, you don't have to separate the carbs. In fact, avoid this if you can. Otherwise you will need to re-sync them.

I've taken mine apart probably 20 or 30 times, so I'm pretty well familiar with their internals, and if you have issues, I can help you out.

I know you mentioned that you went through the ignition system with F64. Did you check that the advance unit was free and returning to the correct neutral position? If it's stuck advanced, then the bike will not want to run below 3000-3400 RPM very well. The cam should turn freely and smoothly. I wrap the cam in rubber and use pliers to rotate it. Be careful not to mar the surface; I'm not sure but there might be easier ways to rotate an advance from a bike with electronic ignition; my '80 has points, but your '81 should have electronic. The big point is not to damage anything.

It might also be a good idea to replace your Carburetor holders (the rubber boots which hold the carbs to the engine). If those are leaking, then the resulting vacuum leak will make the bike run poorly/not at all at low RPM. Z1 usually has them available. They're a bit pricey, but worth if for the sealing. When you get them, be careful not to overtighten the clamps that hold the carbs on; the holders can split if you do. Tighten the clamps until they're just snug; they only keep the carbs from backing out, they don't add any additional sealing.
1980 KZ440-A1 LTD

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Last edit: by gavroyer.
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