Bike still running rich with idle mixt screw seated in

[Jolaflaque]

Hi all,

I have a big problem with my S&S Super E carb on a 91 FLSTF, V&H 2 in 1 pipes.

Owned the bike for 3 years now, and it has always run lean, with erractic idle. ALways suspected air leaks. But it was running fine anyway.
A few weeks ago, saw a fuel leak at the accel pump bushing, decided it was time for a full carb rebuild.

Took it apart, changed throtle plate and shaft, nuts and springs, accel pump, orings and so on. Put it back on the bike, set idle mixt screw at 1 1/2 tuern back, closed enrichener and accel pump, started : wonderful idle, like it's never idled before. Though, black smoke at pipes... Started to close idle mixture screw 1/4 ti 1/4, until fully closed... Bike still idling, and with black smoke at pipes. Had a look at the plugs : both black...

Had a look at jets... Had a .295 intermediate and .72 main. Changed to .265 and .70. Tested again... Same problem !!

Well... Took the carb apart again... Desassembled the accel pump : both orings, balls, one of which with spring, diaphram, everything OK in there.
Checked the float level... Decreased it a little.. OK.
Checked the nozzle oring : OK, right there.

Checked the enrichener plunger : seemed fine, but changed it anyway. It's seating fully right.

Desassembled the throttle shaft and plate, and reassembled... Everything's fine there.

Put the carb back... Closed the accel pump... Tried it throttling... No fuel squirt. Open it a little. Throttle... Fuel squirt OK. Close it back, accel pump working fine.

Started the bike... Start at first time, beautiful idle, but black smoke.. Plugs black in 20 seconds, bike still running with idle mixture screw sated in. I tested the idle speed screw, back off, and the engine dies : throttle shaft and throttle OK.

Tested the coil : seems OK.

I tried to change the mixture screw putting back in place the old one... Same problem. Also put back the old needle. No change !!

Could this be a timing problem.. Don't know what else to check... If you have any idea, they'll be more than welcome.... I'm getting mad !!
Thanks to all.!

[jurneyman]

I am just giving it a process of elimination check, since black plugs could mean the fuel isn't burning completely, it could be low voltage, or contaminated or bad fuel, it could also be caused from fuel seeping around the float valve.

[El Paso Bob]

Had the same problem with my 92 FLSTC. Turned out that I had seated the needle too hard and had a hairline crack in the throttle body. Take the carb off and look in the throttle body from the manifold side; you may find that there is a hairline crack at the tiny intermediate seat. A new throttle body is $$$. If confused, Email me off NG for a pic of mine.

famjones@swbell.net

[Hillside]

My bet on the jetting would be a .028/70, 3 turns on the accelerator pump, 1 1/2 turns on the air/idle screw.

[Hexhead]

I would guess your checking this with the air cleaner off? Does it do as soon as you start it up or after it warms up a bit. Does revving it up clean it out or does it spit black all the time. if so I would do a leak down test on the jugs. Some times cool you'll have good compression but as soon warms up a tad a exhaust valve may be tightening up and dropping your compression. Did you shake the float to make sure it didn't have gas in it? The idle screw only affects the idle (unless it's sneaking passed) so if it does this all the time I would be looking else where. Keep feeding us info.