Author Topic: choke problem cb 750k2  (Read 350 times)

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Offline olasek18_18@o2.pl

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choke problem cb 750k2
« on: September 19, 2023, 06:53:28 AM »
Hello Guys.
I have a problem with start my bike,
when I switch on the full choke, the motorcycle turns off,
the motorcycle does not increase the rpm on choke,
 it starts best without choke and with a bit of gas.

Some problem with carburetor channels or jet?

Offline smee

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Re: choke problem cb 750k2
« Reply #1 on: September 19, 2023, 07:05:41 AM »
Need some more info from you.

What type of carbs do you have?
Is it stock or pods? What jets do you have in? Stock or aftermarket jets?
Carbs balanced and floats set to spec?

Could you be more specific regarding 'it starts best with a bit of gas?' Like blipping the throttle before starting? Shooting ether or starting fluid in the carb intakes?

Petcock/tank clean of debris? Do you have good flow of fuel to the carbs?


With the info you provided, it's most likely a carb problem. I will reserve any advice I may have until you provided us with more info.



Offline olasek18_18@o2.pl

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Re: choke problem cb 750k2
« Reply #2 on: September 19, 2023, 07:40:14 AM »
Carbs Keihin 657A
serial airbox
main jet 120
slow 40

pilot 1 turn off

mac exhaust 4in 1

Offline olasek18_18@o2.pl

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Re: choke problem cb 750k2
« Reply #3 on: September 19, 2023, 07:41:28 AM »
when starter run I just add little throttle

Offline MauiK3

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Re: choke problem cb 750k2
« Reply #4 on: September 19, 2023, 07:46:09 AM »
The choke linkage does not affect the throttle position, only the fuel flow to the engine
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline PeWe

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Re: choke problem cb 750k2
« Reply #5 on: September 19, 2023, 09:10:35 AM »
When engine is really warm after at least 30 minutes ride, set idle to 1200rpm.
This will work fine when riding. Even better take offs.

This make the engine easier to idle when cold too.

Mikuni Smoothbore VM29 has raised idle when using choke. This is by design.

Mikuni TMR has an on-off choke button to pull-push that gives 2000-3000rpm idle.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline ekpent

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Re: choke problem cb 750k2
« Reply #6 on: September 20, 2023, 06:18:57 AM »
The chokes on the early 750's are prehistoric in design. I use mine just on cold start and flutter it back and forth as needed but usually it goes off pretty fast and the faster idle cam is in my wrist. Most don't like to keep running for long at full choke.