Overly rich mixture at Idle - which jet circuit to adjust?

[The Standard]

I have been trying to dial-in the jetting on a set BS34’s on ‘72 stock motor with 2.5” open velocity stacks and 1.25” open TT pipes.

I moved the overall jetting up 2-3 intervals assuming I now have an overly lean AFR with the low restriction intake and exhaust changes.

I am getting white smoke at idle and can smell the fuel - definitely rich. I did notice some fuel dripping out of the overflow hose and got a large wrench and tapped on the float bowls in case stuck floats. By had been sitting for about a month, no fuel stabilizer added.

I sprayed WD-40 on the choke linkage to lubricate.

Bike is kick-only. My usual procedure is a couple of priming kicks with fuel petcocks open, then pull choke all the way out and 2 twists of throttle before kicking with ignition on.

Is this placing too much fuel in engine thus rich smoking at idle?

Do I need to go with smaller jets in any of the circuits or move the needle clip up or down?

I was worried about hole’ng a piston with more air into motor and didn’t think I overcompensated on the jet changes.

Last jetting adjustment was:
130 Air jet
137.5 Mains
45 Pilots
Mixture screw dialed back to 2.5 turns out

Would a larger air jet be best first step or is some varnish somewhere in system the culprit.

I’ll do a ride on freeway and see if that clears things out re. idle condition. Bike doesn’t load up at idle, just smoking.

 

[bazz]

Try 4 .5 turns out on the mixture screws
WD 40 is a water dispersant not a lubricant so use oil instead and make sure the choke plungers are seating

 

[5twins]

Yes, go larger on the air jet. It feeds the idle circuit so that will lean it out a little. A 135 was stock so I wouldn't go any bigger than that. You could also check the float levels. If they are too high, that will cause a rich condition as well.

 

[The Standard]

Reporting back on this.

Returned the Air/Fuel mixture screws to 2 turns out (factory setting) and no improvement. I’ll look at changing the Pilots back to 135’s.

I meticulously set floats before installing carbs when I did the jet changes. @5twins saved the day in alerting me that Clymer manual spec was incorrect. I set them to 22~23mm height.

 

[The Standard]

I also lubed the choke moving parts with oil. When I push the lever all the way in everything looks seated.

How do I confirm the plungers are seated with carbs installed?

 

[Jim]

How do I confirm the plungers are seated with carbs installed?

Do the slide drop test. If the choke's leaking, they'll drop pretty fast.

 

[The Standard]

Assuming carbs have to be off the bike to view the slide motion?

 

[Jim]

Nope, just the air filters. Are you familiar with the test?

 

[The Standard]

I am not. Do I just visually see how fast or slow the slides drop? Compared to each other (carb-to-carb)?

 

[Jim]

Look in Tech (top bar), there's a carb guide that'll walk you through it.

Guess I will too... there's an oval port on the back, at the top. Reach in and push the slide all the way up. Now plug that opening with your thumb or finger and start counting as you let go of the slide. There's no published time for the drop. Personally, I consider anything over about 10 sec as good. If the choke is leaking, it'll drop like a rock.

A suggestion... get familiar with the Tech section. It's a treasure trove of information.