KZ750 Spectre - Stuck Idle fix leading into Stalling

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KZ750 Spectre - Stuck Idle fix leading into Stalling

05 Feb 2019 08:49
#798228
As a bit of background, I recently bought an '83 Kawasaki Spectre, During its look over, it ran fine during the initial inspection and test ride. Since taking it home and riding it for longer times, the bike had a habit of getting stuck at around 3-4000 RPM once fully warmed up. Through searching for help here, I cleaned and rebuilt the carbs a few times, which had no effect, and eventually replaced the petcock. This corrected the issue of the sticking RPM's (huge thank you to everyone on the site that's helped out with other peoples issues.)

Since the petcock replacement a new problem has come up. After five to ten minutes of running, the bike will stall out and die, and wont be able to start back up for another five minutes. I came on another request here about the timing advancer being a possible issue, but I'm apprehensive about playing with that. Does anyone have any advice on what I might be causing the problem?

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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

05 Feb 2019 09:12
#798229
It Looks like your tank cap vent is blocked.
This create a vaccum in the tank so the fuel can´t flow into the carb bowls and lean out the air/fuel mix after
five to ten minutes of running. Try to run the engine with the tank cap open to test if your issue continues or not.
My 1975 Z 1 B 900 Project

www.kzrider.com/forum/11-projects/605133...ears-deep-sleep-mode
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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

05 Feb 2019 09:33
#798230
This might help.
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

05 Feb 2019 09:48 - 05 Feb 2019 09:49
#798231
If not already done, would also assure that valve clearances are within specs.

Too tight valves may allow decent performance until engine attains normal operating temperature and then run poorly and fail to idle.

Good Fortune! :)
1973 Z1
KZ900 LTD
Last edit: 05 Feb 2019 09:49 by Patton.
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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

05 Feb 2019 18:09
#798255
Goes without saying you should do all the bikes normal maintenance tasks right away. Valve adjust in particular. You may chase your tale trying to diagnose running problems on a bike that doesn't have all the maintenance up to date. And the number one reason for a hanging idle is a lean condition, most likely from an intake leak. I'd replace the rubber carb boots and make sure the airbox boots seal tight to the back of the carbs. Then vacuum sync. Some people like to spray stuff on the carbs and listen for a change of engine speed and that does work for gross leaks, but it doesn't work for minor leaks.
Ed
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0

www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

06 Feb 2019 06:55 - 06 Feb 2019 08:56
#798269
PostitiveZero0 wrote: As a bit of background, I recently bought an '83 Kawasaki Spectre, During its look over, it ran fine during the initial inspection and test ride. Since taking it home and riding it for longer times, the bike had a habit of getting stuck at around 3-4000 RPM once fully warmed up. Through searching for help here, I cleaned and rebuilt the carbs a few times, which had no effect, and eventually replaced the petcock. This corrected the issue of the sticking RPM's (huge thank you to everyone on the site that's helped out with other peoples issues.)

Since the petcock replacement a new problem has come up. After five to ten minutes of running, the bike will stall out and die, and wont be able to start back up for another five minutes. I came on another request here about the timing advancer being a possible issue, but I'm apprehensive about playing with that. Does anyone have any advice on what I might be causing the problem?

Good morning.

I would like to take this opportunity to say hello to kzrider.com. May I also compliment you on your style of writing.

Last edit: 06 Feb 2019 08:56 by Olajoe.
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Re: KZ750 Spectre - Stuck Idle fix leading into Stalling

06 Feb 2019 18:37
#798310
Thank you all. I've ordered a set of new carb boots, since the ones I have are at best stiff. I've run a few tests over them with carb cleaner and all that, but as you've all pointed out, any small leak could be a potential problem. I'll try to then run the full diagnostic once everything comes in and give an update to hopefully help any future people who have the same issue.

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