KZR's Bikes of the Month for 2024

Problem with idle

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10 Aug 2021 07:58 #853503 by Hbomb440
Problem with idle was created by Hbomb440
Ok guys back in the garage and so close to getting this bike back on the road finally and now ran into another hiccup. So its a 81 kz750h ltd with keihin carbs that I stripped down cleaned and put back together. When i got the bike it was idling at around 4000 to 4500 and no matter what would not go lower. Started digging into it petcock was shot and needed to be rebuild. The carbs were really nasty and gummed up from sitting a lot and cheap gas. On top of it someone looped carb 1 into 2 and 3 into 4 for overflows guessing there way of fixing overflowing problems from petcock and sticking floats. So everything fixed and back on factory air box and replaced the air box boots.  So i can get it to start up and idle pretty good at about 1000 to 1200. Give it some gas and revs up great but then hangs around 3000. Cant really seem to fix the problem got new carb boots coming for engine side they showed some wear but thought i could get away with it for a bit. Going to recheck the polite holes when i take the carbs back off  seems like its running really lean even turning them out 3 turns but was wondering if it could be something else im missing trying to get the bike out on the road. Also can i vacuum tune the bike or should i just wait?

As always thank you guys this community is so awesome 

81 KZ750H

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10 Aug 2021 08:29 - 10 Aug 2021 08:39 #853506 by F64
Replied by F64 on topic Problem with idle
60/40 test
Tape up half of the airbox.
Is the problem still there?

Remove the tape and crack the airbox open.
Is the problem still there?


Mike Nixon's 60/40 test
www.motorcycleproject.com/text/the_60-40_rule.html
 

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
Last edit: 10 Aug 2021 08:39 by F64.

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10 Aug 2021 08:33 - 10 Aug 2021 08:38 #853507 by F64
Replied by F64 on topic Problem with idle
Multi-post
Ugggh
 

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
Last edit: 10 Aug 2021 08:38 by F64.

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11 Aug 2021 08:14 #853569 by Hbomb440
Replied by Hbomb440 on topic Problem with idle
Thanks I'll give that a try tonight and see what happens 

81 KZ750H

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15 Aug 2021 15:13 - 15 Aug 2021 15:27 #853868 by Hbomb440
Replied by Hbomb440 on topic Problem with idle
Ok did the test and still is doing it hangs right around 3000 to 3500 even with air filter completely out. Pilot holes pluged?

81 KZ750H
Last edit: 15 Aug 2021 15:27 by Hbomb440.

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15 Aug 2021 17:16 #853878 by Nessism
Replied by Nessism on topic Problem with idle
Lean mixture, most likely air leaks is the most common cause for an idle like that.  A bad sync can cause a high idle too.  Plugged pilot jets will cause the affected cylinders to not fire.

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28 Aug 2021 11:11 #854457 by Hbomb440
Replied by Hbomb440 on topic Problem with idle
Ok guys finally got parts in and had some time to work on the bike and still has a very high idle i cant seem to figure it out. New boots on both sides, idle mixture ports are all clear and turned out 2 times. Bench synced again and original was off some. If i close off some air it gets even worse im really lost here also while I had the carbs off the bike rechecked the plugs in the bowls and they looked like they were in and good. 

81 KZ750H

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28 Aug 2021 13:30 #854463 by Mikaw
Replied by Mikaw on topic Problem with idle
Is there any free play in the throttle. Check cables. 

 

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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28 Aug 2021 14:32 #854468 by Hbomb440
Replied by Hbomb440 on topic Problem with idle
Yeah got about 1/16 to 1/8 

81 KZ750H

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28 Aug 2021 14:50 #854471 by Mikaw
Replied by Mikaw on topic Problem with idle

Yeah got about 1/16 to 1/8 
Have you checked the timing advancer. 

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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28 Aug 2021 18:00 #854489 by Hbomb440
Replied by Hbomb440 on topic Problem with idle
No i haven't  not really sure how to and it starts fine and half the time it will idle right until you give it some gas then it just goes up and stays there

81 KZ750H

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28 Aug 2021 18:12 #854490 by Mikaw
Replied by Mikaw on topic Problem with idle
Timing advancer is under the breaker plate. 

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
The following user(s) said Thank You: Hbomb440

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