what dows this do?

[manhunter]

i have taken my carb apart for cleaning since my last ride i ended up riding with my air filter bouncing around in the box. as i dissassembled and cleaned and tested as much of the ckts as possible i ran across a part that i cant figure out what it is i have an idea but not for certain.

when you take the cover off the side of the carb, where the throttle cable attaches, there is a hose that runs from this black devise that looks like some sort of pump. the hose runs up under where the fuel screw is located is this a fuel ckt or an air ckt ? and is there a way i can test it for proper function?

also is there a good diagram of the ckts in this carb(stock 400ex carb)

the problem i am having now is i can get it to fire up if i pump the throttle and hold it open slightly but as soon as i let go of the throttle it dies as if i hit the kill switch.

i appreciate any response

[honda400ex2003]

i believe that is the accelerator pump or the idle cable and adjustment you are talking about my friend. i would say that if it goes through and it has a cover on it, it is the accelerator pump. if you messed with the f/a screw then you should move it back to where it was. i would make sure it is at 3 turns out to get it to idle good again. ill find a schematic of the carb and show you the 2 things i am talking about. steve

[honda400ex2003]

heres the schematic
http://www.bikebandit.com/houseofmotorcycles/showschematic/m2661sch98410

11 is the idle and 32 is the accelerator pump. the pump is in the bowl and goes into the main body of the carb. the idle adjustment is the black thing outside that fights you while putting the bowl back on. steve

[Which 450?]

Whats a ckts???

[killer400ex]

allright, that black thing is not the accelerator pump, it is a bleed line for the choke, the holes above the choke plate on the outer edge run through this and it forces more fuel our of the bowl due to pressure differences, and also try turning your idle screw up, cause when you put the carb back together you might have screwed with the nut that holds the throttle line to the carb up

[manhunter]

ckts=curcuits

thanks steve

in that part diagram th epart is number 28 and i was messing with it today and when i try to start it i can feel the tube is sucking from this part but the part seems to be seized so it is not pulling anything out of it. when i was cleaning the carb i took this piece off and there were 2 small jets in it and when i was blowing it out there was grit in it so i imagine there was some in this "pump like thingy" that has clogged it up.

im pretty sure this part needs replacing but trying to understand what its purpose is will help me in the future when troubleshooting.

thanks for you guys help

[honda400ex2003]

alrighty then killer got it. i thought you were talking about the stuff on the bottom not on the top. lol. steve

[GPracer2500]

It's an air cut-off valve. It richens the pilot circuit during high vacuum situations (such as closed throttle deceleration) to mitigate the lean misfires that can occur under those circumstances.

You can check it's function by removing it and applying a vacuum to the vacuum port (where the hose goes). It should hold the vacuum. With vacuum applied, air should not flow through the two other ports. Air should flow with no vacuum applied.



IMO, more than anything else the ACV is there so the pilot circuit can be as lean as possible for emissions purposes without causing annoying (but mostly harmless) pops on decel. As long as air can freely pass through the ACV, it could be non-functional without causing harm.

$0.02

[manhunter]

so would this make the bike not idle.

i got it to crank but it is lean and crackling but if i let off the throttle ti dies i have more tinkering to do but before i took the carb off to clean i took it around the field and it ran half lap then it died couldnt get it to crank towed it back in and later that night it cranked and would run only if i had the throttle down a little if i let go it automatically died. this is also might have been due to the manifold being cracked and air leaking in? i dunno what do you guys think