This thing will NOT lean out! help

[griffsyj]

I rebuilt my 2150 carb, and set it to the specs on the tech library by michael baxter (thank you for the article btw). I put it back on the jeep, and I cant get this thing dialed in to save my life. Rough rough idle, smoke from the tailpipe, and the smoke smells like fuel. Ive adjusted the idle screws from one end of the spectrum to the other in small incriments, and the choke knob is 2 turns towards lean. I cant get the idle to smooth out at all, and it just seems to smoke worse, no matter what I do.

One thing I'm slightly confused about is it says in the article to lightly seat the mixture screws. is that supposed to mean turn them all the way in until they cant anymore, or turned JUST enough so that theres tension on the spring?

can somebody help me through this, im stuck. Theres no vacuum leaks that I can find at all, and the casting of the carb isn't cracked..I don't know where my problem lies.

[DAHoyle]

Turn them all the way in. Don't over torque them. you will feel when they are seated, then back them out to best lean idle. (engine speed doesn't climb any higher when you go past BLI) You should have a tach with a low speed sensitivity, or a vacuum gauge for this adjustment. I generally use a vacuum gauge.

[griffsyj]

wheres the best place to hook the vacuum gauge up while adjusting? and where should the vacuum typically be at when the screws are set correctly? (around what psi)

[DAHoyle]

wheres the best place to hook the vacuum gauge up while adjusting? and where should the vacuum typically be at when the screws are set correctly? (around what psi)

It should be manifold vacuum. a good place tho hook it would be where the hose to the softball(vacuum reservoir) attaches. Just remove that hose from the nipple on the manifold, and attach your gauge to that nipple.

The way I set it is to turn them all the way in, then out about 1.5 complete turns. That should get you running. Set them both the same to start out with. Then adjust them, most likely counter clockwise, until the vacuum is at it's highest point. turn them back in to see if it drops. If it does, then back out, to the highest vacuum, but no farther. Then do the other one. Once you get that done, your engine will probably idle up a bit, so turn the idle (not your idle mixture)back to where it should be.

Then I fine tune the mixture screws a bit more. Some times you can get them a little better at that point, but not always.

On occasion, you might find that you have a slight "off idle" stumble, When they are set to Best Lean Mix" If so, you might want to give them another half turn or so counter clockwise, and see if it clears up.

This is sort of an off the cuff technique that I use, not necessarily the book answer, but I find that it works very well.

Carburetors are pretty straightforward, when you spend a bit of time learning what makes them work. Just takes a bit of practice, and don't be afraid to ask. I'm sure that if 5 people advised you how to do it, there would be 5 different techniques, all arriving at the same end.

[griffsyj]

Ok, that makes me feel a bit better because I read somewhere that the screws should be a min of 3/4 of a turn but no more than 1 1/2..and i cant even get the think to run unless im at 1 1/2. i turned them out to 1 3/4 and the idle smoothed out a lot but i get that stumbling that you were refering to.

now off to get my new vacuum gauge..apparently my father broke mine when he borrowed it, and neglected to tell me. or he didnt know haha.

I'll come back if ive got more questions. THANKS!

[DAHoyle]

Ok, that makes me feel a bit better because I read somewhere that the screws should be a min of 3/4 of a turn but no more than 1 1/2..and i cant even get the think to run unless im at 1 1/2. i turned them out to 1 3/4 and the idle smoothed out a lot but i get that stumbling that you were refering to.

now off to get my new vacuum gauge..apparently my father broke mine when he borrowed it, and neglected to tell me. or he didnt know haha.

I'll come back if ive got more questions. THANKS!

Yeah, don't pay too much attention to what the settings "should" be. Go with what your instruments tell you, till you get really comfortable. After that, you can fly by the seat of your pants a little, and try to get it tuned to your liking, rather than what the book says. Remember, what you are working on here only effects your idle mixture, and that is only part of the battle. Really, it is the easiest part, once you get the hang of it.

[GWChris]

One thing to be aware of - if the gasket on the power valve is not sealing, it will just pour fuel into the manifold. I have had trouble with this in the past, though mostly while playing with Holley power valves a long time ago.

[griffsyj]

yeah..im screwed, this thing will not smooth out or stop smoking. i replaced the power valve when i rebuilt the carb...and just a little while ago after i got a really bad backfire through the carb. ive got the vacuum gauge on it, got it to the suggested method from above is (where the vacuum is the highest) sputtered every once in awhile so i adjusted the screws just a little more and the sputter has stopped, but the motor is litterally shaking the whole jeep around and still smoking out of the exhaust. i cant figure it out. ive been messing with this carb since 9am and im in the same spot that I was this morning. ive even pulled the carb off and double checked all the adjustments from when I rebuilt it.

[NVJEEPER]

Are you sure there is vacuum at the power valve to hold it closed at idle? The port in my base was plugged solid.

[griffsyj]

yeah im pretty sure because i shot the port clean with carb cleaner. now vacuum GETTING to the hose going to the power valve....is something i can check.brb

[DAHoyle]

One more thing to check.

Are you sure that your float adjustment is good, and that the needle is closing?

[griffsyj]

hmm. i adjusted the float to 7/16ths in the float off position. Maybe i need to bring it down some? like to 1/2?

[griffsyj]

also..yes i am getting vacuum through the line going to the powervalve.

[NVJEEPER]

One thing to be aware of - if the gasket on the power valve is not sealing, it will just pour fuel into the manifold. I have had trouble with this in the past, though mostly while playing with Holley power valves a long time ago.

For sure, mine did not even seat flat on the valve where it would seal to the carb because the hole was like a triangle, had to cut it round so it sealed ( sat nice an flat). An oped needle should push gas out the vent tube.

[griffsyj]

its not the needle. i pulled the top of the carb off and checked. the float adjustment is fine. the next thing is the power valve again i guess. any other suggestions?