Ok, so i have a 96 CBR 600 F3, i just rebuilt the motor, new rings, new bearings, new R/R, new fuel pump, new fuel cutoff relay, new main relay, head was fully rebuilt, carbs replaced with used carbs in good condition, 1200 miles on the motor so far, on my way home from work my return throttle cable snapped, i was able to make it home fine and the bike ran perfectly, i bought a new cable that day and replaced it, i have to remove the whole air-box assembly and the carbs to do so, after i put it all back together and fired it up it ran rough like it was only firing on 3 cylinders, after a while of fighting with it i gave up and put it away, later that night i went out and fired it up again and it ran rough again, i held the throttle open at about 3k rpm's and it finally smoothed out, idled perfectly, ran like a champ, i took it out for a ride, rode fine, would red line no problem and ran strong.... for all of ten minutes, then i came to a stop and it just died, had to push her home most of the way until i finally got it started and it ran rough as hell but i made it home, since then it starts up rough just for a few seconds then runs beautifully, i can ride it around my neighborhood no problem now, still haven't goon to far cause i don't wanna push it for another mile again, If anybody has a clue to what my problem is i need help asap, this is my only vehicle i have right now due to being in a car accident a few weeks ago. Thanks for any and all help in advance.

 

I would try new spark plugs! Only thing i see you didn't replace. Not the major thing i could think of but cheap. Fuel problem could be a stuck float.Did you clean your other set of"used carbs in good condition"? Alot of problems start on these f3 from dirty carbs, fuel pumps, and fuel pump relays.(i see you replaced the fuel pump and relay,but just saying).

 

When the head was rebuilt new NGK plugs were put in, and i did not clean the carbs cause they looked immaculate, also, if the carbs were dirty wouldn't this have been a gradual thing, the bike ran Amazing since its been on the road, then when i pulled the carbs this issue happened with no warning?

 

Check all of the connectors. Look for loose, melted or other-wise damaged spots.
Be sure your plug wires are firmly in the coils.

Due to the sudden onset, I would look more at an electrical cause.
As opposed to fuel/air/carberation.

If all of the connectors are good, inspect the rest of the harness, as well.
Check for pinched/tight runs, melted and/or torn insulation, etc.

Even if it isn't the main cause, it's still time well invested.
Especially if you pack all of the connectors with di-electric grease,
as you perform the inspection.

Hope this helps, Ern