Although this is my frist post i have been a lurker here for a long time! everyone seems very knowledgable so here is my question. I have a 2000 Custom Sportster with a 1200 kit. This motor was originally built in North Carolina by croft custom cycles along with all the other mods. problem is at about 60-70mph in 5th gear it cuts out, not a bog but just surges like crazy and wont accelerate. With very light throttle and i can cruise along fine, but twist on it at all and it surges liek crazy. downshift to 4th and it runs and pulls fine. I have changed everything from plugs to ign module, wires and whatever else you can think of. Pelkin fuel valve is fine, tank is clean too. The carb has a 45 idle jet and a 180 main jet. i was thinking maybe it is lean and changing the main jet to a 185 or 190 and see how it acts. the previous owner is gone so i can get no other info for him. I did talk to the shop that built the bike but the guy that actually built it for my buddy is gone to florida so all i can find out is they rebuilt the whole bike and added the 1200 kit. Was curious what ya'lls thoughts were on this. Idles absolutely perfect,starts fine and runs great in every gear until you hit 5th. Now if I run it wot thru all the gears when i shift to 5th it pulls fine. Just normal cruising and you shift to 5th it cuts out like crazy. Am i missing something? Appreciate any help ya'll might provide.