wondering if anyone got any thoughts? i have a 93 fxstc with a shorty, crane cam, cranes cam ignition and have got a big flatspot while goin down the freeway doin bout 120.

bike rides fine round town its just when i get to bout 120 that it feels like its running out of fuel but twist the throttle and it pulls away no worrys. ive cleaned the carby out and found it to be pretty clean anyway. i have had the bike in a million pieces due to a smash then rebuild so ive only just got it back on the road after about three years. so ive had the ignition out and wonder if its set right. just feel like its starving for fuel at that certain rev though. any thoughts??

need more information m8, like what jets are you useing? what is the timming set at what pipes what cam and what is you cranking compression? what fuel?

 

the s s e carb, and the stock cv carb, are both 40 mm
are you running drag pipes, and without baffles?

i thought the s&s E was 1 7/8"? & the G 2 1/8" the D 2 1/4" in USA they don't measure in metric, the stock cv is a jap carb. but your right the cv40 & the E flow about same air. just the s&s can sometimes run funny at different rev with some pipes.

 

The Super E has a 17/8" (47.6mm) bore and 19/16" (39.6mm)
venturi.

Poorly phrased by me. I meant the venturi is 40mm(well, approx anyhow. they do say 39.6)
which versus the cv40 flows about the same as you say(effectively speaking)

However, as you also point out, the fixed jet carby does not adjust well to all exhausts, esp drag pipes

and as kiwi dave states, this occurs at overlap, curable by

air bleed, to move the overlap
main jet, to reduce the overlap
good baffles in drag pipes
good pipes

I really liked the e in its day, as it seemed a good all round match for shov and evo
But twin cams seem to be easily able to be taken to a point where I have to concede that a mikuni style is prob the way

hi,  set timing  1st  with timing light  you can't jet the carb if the timing is not spot on ,

 the jet sizes for & E carb on & EVBT-80 c.i. is 28 or a 29.5  idle jet   29.5 is safe  ,   main jet is 72 or  74 . mix screw is about 1 - 1 1/2 turns out, 1st jack bike so as to have the fuel tap at the lowest  point  &  dump flush fuel tap  into a bucket  loose about 1 to 1/2 ltr  out  with fuel cap off, even if you have to do it  the 2nd time i bet you will feel the grit as you undo the fuel cock  it  should be done 1 or 2 times a year anyway ,   clean fuel cock before refitting ,  then back blow the jets in the carb,     look down the carb with a torch light &  set the acc pump so it is just working  not too much  fuel on acc pump as it is not needed & will  make it hard to jet  you can bring more acc pump into it later    its the 1 step,     the carb always come last after checking tappets & then the timing then the carb , if you jet the carb to a out of tune motor then you have to go back over it anyway  ,      cheers