KZ650 Jetting Help
- KZer78
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KZ650 Jetting Help
27 Jul 2020 07:50 - 27 Jul 2020 08:02
I have a 78 KZ650 with the stock Mikuni carbs.
Running pods and a 4-1. Stock jets 97.5. Assuming stock pilot jets.
Air screws are 3/4 to 1 turn out.
I knew I'd be running lean, I did a short drive with new plugs and here are the plug pictures.
Cyl 1 on the left, 4 on the right.
I think it's weird that 1 and 3 seem rich and 2 and 4 are lean.
Will bigger jets fix this? Or do I have a weak coil also?
Thanks,
Dan
Running pods and a 4-1. Stock jets 97.5. Assuming stock pilot jets.
Air screws are 3/4 to 1 turn out.
I knew I'd be running lean, I did a short drive with new plugs and here are the plug pictures.
Cyl 1 on the left, 4 on the right.
I think it's weird that 1 and 3 seem rich and 2 and 4 are lean.
Will bigger jets fix this? Or do I have a weak coil also?
Thanks,
Dan
1978 KZ650-C2
Last edit: 27 Jul 2020 08:02 by KZer78.
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- zed1015
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Re: KZ650 Jetting Help
27 Jul 2020 08:12 - 27 Jul 2020 08:13
With pods you must go up a size or two on the main and fit air corrector jets.
www.kzrider.com/forum/23-for-sale/611992...lide-mikunis?start=0
Base rings are mostly clean and this is your mix strength which is on the lean side .
They should have a full turn of light soot.
The rich appearance on 1-3 may be due to leaking choke plungers.
Plug readings only indicate the fueling at the time of shut off so that is the state of running at idle unless you did a plug chop under load at higher rpm.
www.kzrider.com/forum/23-for-sale/611992...lide-mikunis?start=0
Base rings are mostly clean and this is your mix strength which is on the lean side .
They should have a full turn of light soot.
The rich appearance on 1-3 may be due to leaking choke plungers.
Plug readings only indicate the fueling at the time of shut off so that is the state of running at idle unless you did a plug chop under load at higher rpm.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
Last edit: 27 Jul 2020 08:13 by zed1015.
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- Mikaw
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Re: KZ650 Jetting Help
27 Jul 2020 08:28
I’d check the spark or compression on #2. It doesn’t appear to be firing... either it’s so lean it can’t fire...
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.
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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- KZer78
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Re: KZ650 Jetting Help
27 Jul 2020 09:38
I killed the bike under load and coasted to my driveway for the plug reading.
Exhaust of cylinder 2 was hot. It is running.
I will recheck compression. When I purchased the bike last fall, I checked compression, and they were consistent. I don't remember the # though.
I have the air corrector jets, they will be installed when i pull the carbs to rejet.
Is there a way to check choke plungers?
Exhaust of cylinder 2 was hot. It is running.
I will recheck compression. When I purchased the bike last fall, I checked compression, and they were consistent. I don't remember the # though.
I have the air corrector jets, they will be installed when i pull the carbs to rejet.
Is there a way to check choke plungers?
1978 KZ650-C2
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- Mikaw
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Re: KZ650 Jetting Help
27 Jul 2020 09:51 - 27 Jul 2020 10:44
Zed1015 would know, but I’d say if you can just slightly lift the choke lever without and rpm change then you might have a plunger leaking.... adversely if you do start to raise the choke lever and [strike]no change[/strike] then they should be good...
Edit.... I just noticed a mistake....
Adversely if you raise the choke lever and you do get an rpm change then the seat might be good...
Sorry
Edit.... I just noticed a mistake....
Adversely if you raise the choke lever and you do get an rpm change then the seat might be good...
Sorry
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.
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Last edit: 27 Jul 2020 10:44 by Mikaw.
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- zed1015
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Re: KZ650 Jetting Help
27 Jul 2020 10:06
The choke plungers will be leaking, they all are at 40 years old but it is to what extent.
The sooting may be due to other issues such as oil burning, leaky guide seals or worn ring etc and the overly lean plugs may be due to leaking intake boots on top of increased air from fitting the pods.
The plungers are obsolete and currently i am the only person world wide who offers a Viton re-seating service.
I've just done one set and the user reported that the gas mileage went from 29 to 42 mpg just from that.
There's no real way to test them apart from what Mikaw suggests but even that method may not be conclusive if other problems exist.
I would fit the air correctors and larger mains before you go any further and see how you go from there.
The sooting may be due to other issues such as oil burning, leaky guide seals or worn ring etc and the overly lean plugs may be due to leaking intake boots on top of increased air from fitting the pods.
The plungers are obsolete and currently i am the only person world wide who offers a Viton re-seating service.
I've just done one set and the user reported that the gas mileage went from 29 to 42 mpg just from that.
There's no real way to test them apart from what Mikaw suggests but even that method may not be conclusive if other problems exist.
I would fit the air correctors and larger mains before you go any further and see how you go from there.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
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- KZer78
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Re: KZ650 Jetting Help
27 Jul 2020 14:38
I found some 110 jets sitting around.
should i try those? or are they way too big?
should i try those? or are they way too big?
1978 KZ650-C2
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- zed1015
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Re: KZ650 Jetting Help
27 Jul 2020 15:08
110 to 112.5 are a good place to start.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
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- KZer78
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- KZer78
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Re: KZ650 Jetting Help
04 Aug 2020 05:33
I installed the air corrector jets and wow, seems like a different bike off the line.
I installed 110 main jets, but haven't done a plug chop yet.
At midrange RPM the bike sputters and power drops off.
I think i need to raise the needles correct?
I'm 90% sure i have the needles in position 3. Should i drop 1 step at a time or go all the way to position 5?
I installed 110 main jets, but haven't done a plug chop yet.
At midrange RPM the bike sputters and power drops off.
I think i need to raise the needles correct?
I'm 90% sure i have the needles in position 3. Should i drop 1 step at a time or go all the way to position 5?
1978 KZ650-C2
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- zed1015
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Re: KZ650 Jetting Help
04 Aug 2020 07:47
I'm pretty sure the 650 stock position is 4 so you need to lift it a notch to get it to stock which may also cure the hesitation.
Feathering the choke at the point of the stutter is a quick way to see if you are lean or rich.
If the the choke cures the hesitation you are lean and vice versa.
Feathering the choke at the point of the stutter is a quick way to see if you are lean or rich.
If the the choke cures the hesitation you are lean and vice versa.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
www.kzrider.com/23-for-sale/611992-air-c...lide-mikunis?start=0
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- KZer78
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Re: KZ650 Jetting Help
04 Aug 2020 08:06
Good point on the choke. I will check that out.
1978 KZ650-C2
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