Carb tuning

Ethan B
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25 Jun 2022 16:59 #869356 by Ethan B

Carb tuning was created by Ethan B

Hi guys!

I'm riding a 1981 Kz750 LTD 4 strokes. Just finish cleaning the carbs and tuning them. The bike is idling fine. When in first gear it automatically dies when I pass 2500 rpm (no throttle response what so ever). Before changing the jets it was running quite well. So here's what I'm running in the carbs:

-137.5-k main jets in cylinders #1 and #4
-140-k main jets in cylinders #2 and #3
-62-k pilote jets in all 4 cylinders
-Lowered de needles by one spacer

Just so you know, I tune the carbs cause I'm running JBS pods filter and my exhaust are empty inside. My first thought is that I might be running too rich and I'm flooding the carbs, if so what should I change? Main jets? Pilot jets? Which size I should I get and where to find them online?

Thank you for any advice!

Ethan B.

IMG_0904.MOV

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Nebr_Rex
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25 Jun 2022 18:33 #869360 by Nebr_Rex

Replied by Nebr_Rex on topic Carb tuning

DynoJet jet kit.

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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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Ethan B
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26 Jun 2022 08:39 #869381 by Ethan B

Replied by Ethan B on topic Carb tuning

Thank you!

According to their website, I should be running either 126 or 130. Just check my plugs and they are completely toasted... Think I just found out my issue.

Ethan B

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Nebr_Rex
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26 Jun 2022 16:04 #869397 by Nebr_Rex

Replied by Nebr_Rex on topic Carb tuning

DynoJet uses adifferent number scale and you will need more than the main jet.
Buy the kit it will save you from the aggravation.

.

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Nessism
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27 Jun 2022 16:55 #869439 by Nessism

Replied by Nessism on topic Carb tuning

wrote:
Buy the kit it will save you from the aggravation.

.

This, plus install a baffle in the pipe. Open pipes are annoying as F**K

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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howardhb
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God, I trust

30 Jun 2022 07:59 - 30 Jun 2022 08:02 #869612 by howardhb

Replied by howardhb on topic Carb tuning

Looks waaay too rich.
That black sooty carbon is conductive, and will cause all sorts of rough runnjng problems.

Carbon deposits can be burned off by butane or propane blow-torch, heating the electrode end to a dull red and letting it cool. Resist the urge to use a wire brush.
If you have access to one, a spark-plug sand-blast cleaner will work.

Dynojet have a nice detailed explanation of how to diagnose rich or lean running. I'll search for it and post it here...

H.

'81 GPz 550 D1
'81 GPz 1100 B1 ELR "Tribute" www.kzrider.com/11-projects/617040-1981-...-rstomod-elr-tribute
'82 Yamaha YB100 Fizzie
'79 Suzuki GT200 X5 TWO STROKE TWIN - SMOKER!

Last edit: 30 Jun 2022 08:02 by howardhb.

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daveo
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04 Jul 2022 16:26 - 04 Jul 2022 16:26 #869873 by daveo

Replied by daveo on topic Carb tuning

I wonder if the baffle exhaust coloration is a good indicator of carb jetting, and spark
plug condition.

1982 KZ1100-A2

Last edit: 04 Jul 2022 16:26 by daveo.

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Warren3200gt
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05 Jul 2022 10:21 - 05 Jul 2022 10:28 #869912 by Warren3200gt

Replied by Warren3200gt on topic Carb tuning

That'll work as long as it don't back fire and suck it back in.
You might want to think about a tie strap to stop that happening and you may experience slightly retarded ignition.