rough running '89 FXST

[crownmotorz]

I just got my 1989 FXST put back together after rebuilding the motor. It fires up without hesitation and idles pretty smooth.. Once I try to bring it up off idle it seems like it starts to misfire.

Sometimes it seems like its the carb and then other times it seems like it is the ignition.


the motor is a 96" stroker running the crane hi-4 single fire ignition. I am running an s&s super e carb. I am not familiar with this carb so any help would be appreciated.

I went up to a 32 idle jet on the carb and I cant remember what i am running on the main jet. I looked this morning but i forgot.

after some adjusting it seems to have a flat spot around 1/4-1/2 throttle but at wide open throttle it seems to pull good but has a very bad vibration, which leads me to believe it is ignition.

what is a good base setting for the hi-4 single fire ignition. I have the three trimpots advance timing on top, rev limiter in the middle and rear cylinder on bottom.

[RustyShackleford66]

Please tell us about your short 2 inch drag pipes and how great they sound.

[BrokenSprocketGarage]

How did you set the timing? Are you using a VOES? What air filter and exhaust are you using?

[jerseykat1]

Have you checked the plugs? Do they look rich or lean? What's the last thing you did to the bike before this problem?

[crownmotorz]

Please tell us about your short 2 inch drag pipes and how great they sound.

1 3/4" and they sound great. maybe i should change them to 2" and that will cure my problem.

[crownmotorz]

How did you set the timing? Are you using a VOES? What air filter and exhaust are you using?

no voes switch, I am running the FMA shorty velocity stack, and I am running some shorty drag pipes that where built from the previous owner.

The velocity stack and exhaust are something I can not part with so I am willing to take a hit in the performance department.

I set the timing with front cylinder at top dead center and then turned the module until the light went out.

[crownmotorz]

Have you checked the plugs? Do they look rich or lean? What's the last thing you did to the bike before this problem?

The last thin i did before this problem was rebuilt the whole motor........

I made some progress this afternoon and I re-timed it. It seems to be running much better, the pins holding the module in where loose I probably forgot to tighten them after I timed it because that is the dumb shit that I do.

[antblyme]

Throw the stock s&s air cleaner on (or any air cleaner) and see if it solves the problem....I have a 96" EVO and could never get it tuned with a velocity stack. Same exact symptoms as u described above