Carbs

[750head]

Hi. My bike blow black smoke when its revved. My third butterfly dont want to open when busy sync. What can i do

[hardlydangerous]

clean and lube the throttle shafts and linkages. Make sure they are moving freely.
Also check the choke cable free play and make sure its routed along side the throttle cables and down the center cutaway under the tank. If you choke cable free play is not enough or the cable is binding it will hold the choke open.

[750head]

Thanks. Done that and check the choke, but still black smoke

[steves]

Is the spring in place on the throttle linkage? How do you know that #3 isn't opening? Did you have the carbs off?

You are certain nothing is binding or caught?

[750head]

Yes, i took it off. It opens by hand but when i adjust it with the screw it doesnt open. Cant get it sync like that.

Adjustment screw between carb 1 and two opens 1. Between 3 and 4 opens 4. Between 2 and 3 only opens 3.

[steves]

Do all four open with the throttle cable?

[750head]

Yes

[steves]

Is the adjustment screw backed all the way out, and not actually moving anything when turned?

[750head]

Yes. It opens butterfly 2.

[steves]

Screw 1 adjusts # 1 to 2
Screw 2 adjust # 2 to 3
Screw 3 adjust #3 to 4

First adjust #1 to #2
Then adjust #3 to #4

Then use the middle screw to adjust #3 to #2

Repeat as needed.

Something may be WAY out of adjustment. Read in the wiki, under carbs 101 how to do a bench synch.

[H-2 CHARLIE]

LIFE IS NOT ALWAYS EASY ..........

[loudnlow7484]

Like Steves said, the screws adjust 1 to 2, 3 to 4, and then the set of 1&2 to the set of 3&4. I can't remember off the top of my head, but the throttle cable is directly connected to either 2 or 3, so no amount of twisting the adjustment screws is going to open or close that particular butterfly. If you need that one open more in relation to the rest, then you need to close the rest of them to match it instead.

[steves]

Usually visual synch starts by setting #3 with the idle screw then balancing the rest to match.

[750head]

Between carb 1 and 2 and between 3 and 4 there is nipples that can swing up and down, isnt there supposed to be a pipe on to link them? I know i sound dumb!

[steves]

There should be a piece of brass pipe that goes from the bottom of each carb to the top. Can you get any pictures?