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TOPIC: KZ750 Spectre - Stuck Idle fix leading into Stalling

KZ750 Spectre - Stuck Idle fix leading into Stalling 05 Feb 2019 08:49 #798228

  • PostitiveZero0
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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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KZ750 Spectre - Stuck Idle fix leading into Stalling 05 Feb 2019 09:12 #798229

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It Looks like your tank cap vent is blocked.
This create a vaccum in the tank so the fuel canĀ“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.
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KZ750 Spectre - Stuck Idle fix leading into Stalling 05 Feb 2019 09:33 #798230

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This might help.
Steve
Z1b1000 1975 Z1b
Opinions expressed by me do not reflect those of the the staff or members
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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KZ750 Spectre - Stuck Idle fix leading into Stalling 05 Feb 2019 09:48 #798231

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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
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Last edit: by Patton.

KZ750 Spectre - Stuck Idle fix leading into Stalling 05 Feb 2019 18:09 #798255

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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.
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KZ750 Spectre - Stuck Idle fix leading into Stalling 06 Feb 2019 06:55 #798269

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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.
ZX12R
1981 KZ1000CSR-M
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Last edit: by Olajoe.

KZ750 Spectre - Stuck Idle fix leading into Stalling 06 Feb 2019 18:37 #798310

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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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