cb750 running very rich

[hood624]

i have a 77 cb750k has 120 main 42 slow jet bike has air screw turned out between  half and three quarter out from all the way in and bike got black smoke coming out of pipe wife following me home said she had to stay back because the gas fuses where so stop coming from the bike what do i need to do

[TOOLS1]

120 is pretty big! Depending on modifications made to intake/exhaust I would go down to a 110, and tune from there.
TOOLS

[shinyribs]

I have a 76 F with an open 4-1 exhaust.

When I had pods on the bike I was running 125 mains and 42 pilots. Air screws were at 1.5 turns.

When I returned to stock airbox and filter I had to rejet to 110 mains but left the 42 pilots. Air screws still at 1.5 turns.

Runs perfect. Upper 40's fuel mileage and no flat spots anywhere.


BUT,you have keyhole carbs vs my roundtops. If your bike has stock carbs,that is.

What do you have for exhaust,air box/filter? And are you still running stock keyholes carbs?

[hood624]

i have foam pods on the bike with a vince and hines pipe with 4-1 header and  have the needle clip on the second one down a guy on here told me i needed to put 120 and buy new adjustable needles and put them in middle position i did it and it would run right and ended up having to put it up on on the needle

[TOOLS1]

hood624 wrote

i have foam pods on the bike with a vince and hines pipe with 4-1 header and  have the needle clip on the second one down a guy on here told me i needed to put 120 and buy new adjustable needles and put them in middle position i did it and it would run right and ended up having to put it up on on the needle

Could you clarify this a bit?
TOOLS

[LukeM]

Here, TOOLS:

. . , , . . ... . . . . , . . ! ! ! ?

Put those in random places on his posting, and it should make better sense.

For the humor impaired:



Luke M

[hood624]

the bike has uniflow foam pods for air filters and 4-1 header with vinces and hines pipe and i was told on here that i needed to buy adjustable needles so the bike would run right since this bike only comes with a needle that is a nonadjustable needle so i bought the adjustable needles and put it on the second groove from the top of the needle and was told i needed to buy 120 main jet and 42 slow jet the bike seems to be running very well just people behind me have said that it smothers them out the gas fume smell


................ there you go LUKE M i thought we was through with English class i would like you to proof read this one for me i must need more help then i got in school .,?

[shultz_1978]

I read it pretty easily< But hay I never made it through high school. hahaha  rather play with wrenching on cars at the time.

Is it running rich all the time or idle, middle or all the time.? Check the plugs adjust the mixing screw.

Tools?

[shultz_1978]

Is this what  your carbs look like?

Okay may be not black. But you know

[shinyribs]

LukeM wrote

Here, TOOLS:

. . , , . . ... . . . . , . . ! ! ! ?

Put those in random places on his posting, and it should make better sense.

For the humor impaired:



Luke M

Probably one of my all time favorite posts to date.

[hood624]

Its running rich all the time at idle you can see black smoke puffing out of the exhaust pipe but when running the fume smell from behind the bike is horrible choked my wife up and those carbs look just like those

[shultz_1978]

I would say try dropping the mains 1 notch. Just what I think. You will be come a pro with taking these carbs off by the end.

I think their is no one sweet setting that works one all carbs. Some one my be able to get you close but in the end you will probable find the setting that work best for you on your own.

I am by no means saying not to ask any thing a long the way. Gives some of us more learning info and some pride in helping out.

[TOOLS1]

If it is putting out black smoke at idle, and all through the RPM range, you have more then a main jet problem. How did you change the pilot jets? You might have cracked a carb body.
TOOLS

[Lucky 1]

WOW...No wonder it is running rich!!! Read on.

The mixture screw should only be about 1 full turn out from lightly bottomed.
Make sure all 4 mixture screws have the O ring and washer.
The O rings should not be all wonky or chewed up.
The O ring goes in first, then the washer ,then the spring ,then the needle.

Make sure the accelerator pump system is operating correctly.

120 mains and #42 slow jet is correct for that set up.

BINGO!!!

The slide needle should be on the 2nd groove down from the top.
The stock position was groove #1 from the top.

[hood624]

i know that the accelerator pump is working when in i turn the throttle it squirts fuel out of all four the carbs but i looked at the manual but it wasn't easy to understand but how do i know that the accelerator pump is my problem squirting fuel while normal riding it should just squirt fuel and stop right or can someone tell me a easy way to check it

[TOOLS1]

It's not the accelerator pump unless you just keep opening, and closing the throttle. The accelerator pump only squirts when you twist the throttle open.
TOOLS

[hood624]

LUCKY ONE  i have got everything set like you have said rechecked the float height and checked to make sure everything was in the air fuel screw when i pulled them out it was the air screw the spring the washer and the o ring which is what you said  but i having black smoke rolling out of the exhaust and horrible mileage like 80 miles to a tank what do you think is making all this smoke and fume smell it keep people off my ass but the bike runs great just smoke pretty bad

[hood624]

and one thing i forgot to ask was when i was checking to make sure all the clips where in the second position on the needle was there is a small hole in all the sliders i not sure if this can be put together wrong but is the hole supposed to be open or covered by the link arm

[hood624]

anyone help or input would be great

[hood624]

IS this the color that the plug should be i put brand new plugs in and held it at 4000rpm for half a mile to almost a mile and then pulled clutch in and shut the motor off and this is what the plugs looked like the inside where alittle lighter this is the outside plug if this is the right color to be running right what do i need to try next