New plunger black plugs

Nessism
Offline
Sustaining Member
Registered
Posts: 7777
Thanks: 3159

Re: New plunger black plugs

22 Jul 2025 07:23

Several model of Suzuki GS bikes used richer main jets in the center two carbs compared to the outside carbs. Airbox flow? Maybe. I assumed it was because of cooling differences, with the center cylinders running hotter. Anyway, one step difference on the mains shouldn't be a dealbreaker. Of course, the proof is in the doing, and this bike shows rich on the center cylinders, particularly #2. Something may be wrong outright with that carb.

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

The following user(s) said Thank You: Maxbou92

Please Log in or Create an account to join the conversation.

Wookie58
Away
Moderator
Registered
Posts: 5182
Thanks: 3183

Re: New plunger black plugs

22 Jul 2025 07:40 - 22 Jul 2025 07:42

#914948

Nessism wrote:

Several model of Suzuki GS bikes used richer main jets in the center two carbs compared to the outside carbs. Airbox flow? Maybe. I assumed it was because of cooling differences, with the center cylinders running hotter. Anyway, one step difference on the mains shouldn't be a dealbreaker. Of course, the proof is in the doing, and this bike shows rich on the center cylinders, particularly #2. Something may be wrong outright with that carb.

I remember broaching this topic a long time back and I got "shot down" for even suggesting it. Many years ago I ran the centre cylinder on my KH400 (with pods because the mono shock filled the air box space) richer - 1 slot on the needles - and it ran perfectly with even coloured plugs (I appreciate the centre cylinder running hot was more of an issue with the 2 stroke triples)

1982 KZ1000 Ltd
www.kzrider.com/forum/11-projects/617631...-82-begins?start=192
kzrider.com/filebase-alias?view=download...d-fault-diagnosis&ca

Last edit: 22 Jul 2025 07:42 by Wookie58.

The following user(s) said Thank You: Nessism, Maxbou92

Please Log in or Create an account to join the conversation.

Maxbou92
Topic Author
Offline
User
Registered
Posts: 216
Thanks: 10

Re: New plunger black plugs

22 Jul 2025 07:44

#914949

Thank you man.. all is done with these carbs!! Ultrasound cleaning, mechanical synchro.. a lot of valve has been corrected by machinist before my rebuilt.. last guy has make wrong timing and bent a few valve!! Now everything is on specs.. dont know what to do, I will try to put 102.5 instead 105 like Zed suggest me.. last night I took hot compression.
1 : 165
2 : 163
3: 157
4: 160

Kz750e 1980

The following user(s) said Thank You: Gdizard, Wookie58

Please Log in or Create an account to join the conversation.

Nessism
Offline
Sustaining Member
Registered
Posts: 7777
Thanks: 3159

Re: New plunger black plugs

22 Jul 2025 08:27

#914951

One other thing to try...

Remove the spark plug caps on the center cylinders, and measure resistance. They unscrew from the wires. Should be something in the range of 5000 ohms. Inspect the spark plug leads, and snip off about 5mm off the end, before screwing the caps back on. If the cap shows high resistance, you can use a flat blade screwdriver, and open up the cap, for checking the resistor inside.

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

Please Log in or Create an account to join the conversation.