Looking for help...

I picked up a 1999 Sportster 1200 Custom for my wife a few months ago. It ran great for a month but then all of a sudden it's been running like crap. It first started out during her training. The bike fell on it's face on upper RPM's and the tach would go whacky. I replaced the battery, but the bike still stumbled on upper RPM's. I've since changed out the coil, plugs and wires. I've checked the plugs and they're ok. I double checked the battery connections. They're clean and tight. Plus I even tried putting the stock mufflers back on. Still it is weak on upper RPM's. It's as if it wants to go but it can't. Something is holding it back. It stumbles.

Fuel is ok. I've pulled the air cleaner off while it's running and it's spraying fuel. I even sprayed carb cleaner inside to see if it needed a little cleaning.

Any ideas? My next step is the voltage regulator but don't want to waste $135.00 on that before checking to see if anyone else has any ideas.

 

Have you replaced the ignition module?

 

No I haven't swapped that out. Is that a possible culprit? I feel like a bad tech at a dealership swapping party's out til I find the cause.

 

On mine, was electrical. Leads to the coil were loose. Recrimped them. Tach would go crazy. U replaced your coil, so guessing u checked the leads for tightness. Got to be electrical. Something loose or dirty?