air leak, bad petcock or bad timing advance?

[youstolemybeer]

Hi again, so the bike 1981100g kerker 4to1, idles fine until it warms up, then it wont idle below 2000rpm, if i gun the throttle to 7000rpm and release, the idle will drop to 1000 for about a minute. Then it will creep up to the 2000.
Airbox sealed
new o-rings and intake boots
took the airbox boots off, nice and soft
Changed the clamps for airbox and carbs
vaccum line at # 2 carb good and tight.

Thinking about putting the petcock on prime, seal the vacumm port and see if that changes anything, but am concerned with over filling the fuel bowls. Will the float valves have enough umph to shut off the fuel with the petcock open freely?
Any ideas?
Love the site, whoever came up with this is a saint.
BikeCliff= THANK YOU for your site. It appears that a lot of hard work went into it. Your work is very much appreciated.
Steve

 

[tkent02]

Thinking about putting the petcock on prime, seal the vacumm port and see if that changes anything, but am concerned with over filling the fuel bowls. Will the float valves have enough umph to shut off the fuel with the petcock open freely?

It should be fine, just don't leave it on Prime when the engine is shut off.
Is the vacuum line old and crappy?

 

[Guest]

You seem to have covered your bases with a vacuum leak but that is the symptom of one.

 

[youstolemybeer]

the vac line is new. gonna try the petcock thursday, wish me luck


Thanks for the replies
Steve

 

[dcil]

This may sound stupid but, if you turn your idle adjustment it dies I assume? You didn't mention adjustment so I thought I'd ask. My cable was to tight and well you get it. But otherwise almost has to be some sort of vac leak. Gotta love our carbs.

 

[motman]

Wait, so the vacuum ports are those two ports on the 2nd and 4th carbs??

Because this sounds exactly like my problem, but after I replaced the intake boots it made it worse!
So are these vacuum lines aren't supposed to be attached to anything right? Just the tubing that goes back by the battery, right? If so I think I just need to replace those.

 

[dcil]

just the single port on I believe carb number 2. the other ones are bowl vents

 

[SqDancerLynn1]

Petcock vacuum is on the intake side of the #2 carb on the BS carbs The engine doesn't care if the petcock is on ON or Prime when the engine is running makes no difference as long as you turn it off when you turn the engine off. You do loose the reserve function when on prime

 

[Guest]

Wait, so the vacuum ports are those two ports on the 2nd and 4th carbs??

Because this sounds exactly like my problem, but after I replaced the intake boots it made it worse!
So are these vacuum lines aren't supposed to be attached to anything right? Just the tubing that goes back by the battery, right? If so I think I just need to replace those.

Those are vent lines. I don't run hoses on them at all.

 

[youstolemybeer]

well its not the petcock. idle still comes up,From 2000 rpm with a load, it farts and pops a little like its running lean, but the plugs are black and sooty (i guess thats a word)

Aside from spraying the carb boots with wd-40 or carb cleaner, is there another way to check for vacuum leaks?
Thank you for everything so far
Steve