Choke/Idle Issue

[zooki91]

I recently went through carbs 101 (thanks special K) and got it running alright. I have to put the choke on all the way to start it which to me would be expected... once its cranked it only stays idle with the choke on (around 1300-1500rpm. So i give it a few revs and on the way down the needle stays at 3000-2500 rpm. So i slowly turn the choke to the leaner side and it'll start to go back to normal slowly but once it gets there it dies out. Seems to me like the choke is sticking or something.

Any ideas?

[Kreylyn]

I recently went through carbs 101 (thanks special K) and got it running alright. I have to put the choke on all the way to start it which to me would be expected... once its cranked it only stays idle with the choke on (around 1300-1500rpm. So i give it a few revs and on the way down the needle stays at 3000-2500 rpm. So i slowly turn the choke to the leaner side and it'll start to go back to normal slowly but once it gets there it dies out. Seems to me like the choke is sticking or something.

Any ideas?

Choke is not a choke, it's a fuel enrichment system.

Pull the lever, it opens the plungers on each carb, pulls fuel from the bowls and adds it to the mixture being pulled into the engine. Cold engines start better with a richer mixture. Hot engines run poorly with a richer mixture.

If you "blip" the throttle and the idle rpms hang high.... then your idle circuit is lean.

If the idle is bouncy... you have a vacuum leak.

If you "blip" the throttle and the idle drops immediately to about 1k or so and then slowly fades out to quit... your rich on the idle circuit.

Those are the basics... there are other possible issues, and symptoms to look out for, but... that will generally get you started in knowing what's going on with the carbs.

Thinks to know about the idle circuit...

You must dip the carbs to fully clean the circuit. Carb spray alone will not get it clean. Fuel flows from the main jet and emulsion tube area into the pilot jet area (black plugs seals it off) and if not dipped, then that hole will sometimes still be varnished up and you can't flow enough fuel to the pilot jets.

The A/F screws should be set at 2.5 turns out. If those were not pulled and checked, that could be another issue.

Krey

[1990gsx 600]

i have the same issue. mine will start and rev up to about 6k and then slowly come down to about 4k as i turn the throttle off the engien will idle at about 1k but its barely alive then it will die if i rev the engine then it will run up to around 3k again and then take about 40 seconds to win back down to 1k to slowley die

[zooki91]

Choke is not a choke, it's a fuel enrichment system.

Pull the lever, it opens the plungers on each carb, pulls fuel from the bowls and adds it to the mixture being pulled into the engine. Cold engines start better with a richer mixture. Hot engines run poorly with a richer mixture.

If you "blip" the throttle and the idle rpms hang high.... then your idle circuit is lean.

If the idle is bouncy... you have a vacuum leak.

If you "blip" the throttle and the idle drops immediately to about 1k or so and then slowly fades out to quit... your rich on the idle circuit.

Those are the basics... there are other possible issues, and symptoms to look out for, but... that will generally get you started in knowing what's going on with the carbs.

Thinks to know about the idle circuit...

You must dip the carbs to fully clean the circuit. Carb spray alone will not get it clean. Fuel flows from the main jet and emulsion tube area into the pilot jet area (black plugs seals it off) and if not dipped, then that hole will sometimes still be varnished up and you can't flow enough fuel to the pilot jets.

The A/F screws should be set at 2.5 turns out. If those were not pulled and checked, that could be another issue.

Krey

i followed carbs 101 to the T. My a/f screws are out 2 turns so maybe i am running lean. when i get it idling nicely is the the a/f screws i turn to sync them? and then also isnt there another screw that tunes the carbs in pairs?

[bob393]

2 turns on the A/F could be a bit on the lean side.

No the A/F screws are not used for syncing the carbs. That is done with screws on the throttle rod from the top. Left screw first, 3&4, than the right screw, 1&2, than the center screw bank 1&2, bank 3&4.

[zooki91]

thanks man, PAkat helped me out alot on this subject. Now i just gotta take my carbs off again

[Batgirl]

carbs off again

I think I'll start my own club .... "how many F***** times do I have to take these carbs off" club.

Hope you don't become a member!

[zooki91]

I think I'll start my own club .... "how many F***** times do I have to take these carbs off" club.

Hope you don't become a member!

I been a closet member for a 6 weeks now.

Fortunately I'm making progress. I wish i had an a/f adjustment tool. Tired of taking the carbs off to turn them.

[bob393]

.....I wish i had an a/f adjustment tool. Tired of taking the carbs off to turn them.

Aint that the truth!

[twerth]

I wish i had an a/f adjustment tool. Tired of taking the carbs off to turn them.

I bought one of those recently and still remove the carbs to adjust the screws. The tool is difficult to use and the curved part flexes inside the tube making it almost impossible to be accurate with your adjustments. Maybe there's a trick to it. I also had to modify mine so the screwdriver would go deep enough to engage the A/F screw head.

[zooki91]

I bought one of those recently and still remove the carbs to adjust the screws. The tool is difficult to use and the curved part flexes inside the tube making it almost impossible to be accurate with your adjustments. Maybe there's a trick to it. I also had to modify mine so the screwdriver would go deep enough to engage the A/F screw head.

that sucks