I have a 92 sportster 1200, while riding to work the other day it started missing and coughing when gas applied, it idles fine, I got it home cleaned carb, checked intake seals, still no go, switched to a older carb that ran fine, no go, tried new ignition and replaced the ignition plate sensor and coil. still starts fine but as soon as gas is applied it coughs out the carb, backfires out the exhaust. the headlight dimms as it coughs. any ideas.... ?

 

this may seem simple......try to drain the tank and put some new gas in it. It may be bad gas!

 

Already drained all the gas and put in fresh, also checked the VEOS switch just by blowing in the vac tube to make sure it changes state, but I don't think that switch could make it run this bad. can the voltage regulator make it cut out?

 

Check voltage, try another battery. Also could be time for some new plug wires

 

Sounds like something electrical from what you describe.

 

Didn't see any mention of checking the plugs, did you do that? Is it running like crap when engine is still cold and warming up, or only after the engine is fully warmed up? Can you slowly roll the thottle up to eliminate issues with the accellerator pump. Does it happen with the bike sitting and reving the thottle, does it happen only under heavy accelleration. Did you really clean the carb, you need to soak it in carb cleaner for a few hours with it completely dissassembled, then blow out all the passages directly with carb spray, then follow up with flash drying with compressed air, also blowing out passages. Make sure you're running a good battery, and check running voltage as well. And I hope you weren't checking the voes switch by blowing into it, it requires vacuum to switch. Have you tried bypassing the voes, simply pull the vacuum line and plug the nub on the carb, then run the bike. Based on what you said, it's simply not enough to really say anything about what's wrong. So for now, the suggestions i mentioned and others have mentioned are all valid things to check out. Try to narrow down the problem, if you don't have a manual, get one and start flowing through the trouble shooting procedures. And don't go buying parts if you can't varify that their bad, your just throwing your money away!