Hey Guys !!

Im new here, But a brother of mine suggested I ask the "interwebs" and see if anyone has any ideas for a solution to my problem.

Ive got a 1993 FLSTF that Ive had for a few years.

Its got a CV carb, just rebuilt with all the right Jets for my altitude. (4500ft) and a new CV Performance slide, and needle jet.
Its got an S&S Hi-4N ignition modle.
and the top end was just rebuilt.
Over the weekend I put in the new slide and replaced the Vacuum switch behind the carb.

Ok introductions out of the way, this is the issue. (and it doesnt ALWAYS happen)

I start the bike up, to head to work, or to head home. Let it warm up for about 5 min or so. Until it Idles on its own. It ran to the end of the block like a work of art. turned the corner and it back fires. runs like it’s gonna die for like a mile or so. By the time Ive run another mile, you’d never know there was a problem. runs like a dream. idles at the light like smooth as silk. no sneeze on take off. putts into work like a dream.

I go to leave at 5pm, bike fires right up. Off Choke and idles fine. Leave the parking lot. . . fine. Around the corner and onto the main drag, into some traffic, cough, spit, BANG backfire. She throws a fit for about a mile and a half. Loses power, surges, the whole thing. Then POOF the problem is gone. Purrs like a kitten for the rest of the ride home.

I even went so far as to pull my timing sensor from the points cone, and check for oil in the sensor eyes. Yup there was a smear. Not alot. Wiped it all out, and shot some contact cleaner through the eyes to make sure I didnt miss any. Left for work. . same thing.

So, does anyone have an idea?

thank you for your time.

Cecil

 

start by pulling the plugs and see how they look ...
we would not let it idle for "5 mins " neither ...
fouled plugs ???...like a 2 stroke ..when the plugs clean up ...it hauls *** !!!
your idle mix screw may be too rich ??? or slow jet too big ...