Recently I've been having issues with my 03 sportster. After it is warmed up every once in a while it will backfire and lose power almost like it is running out of gas. If you give it about 1/4 gas and don't rev it too high it will drive but sputters and backfires a lot. When it is not doing this it runs perfectly fine with out any issues and still has plenty of power. I have changed the spark plugs and wires last week. Any other suggestions as to what it could be?

 

Decel pops and backfires are usually caused by a lean fuel mix. Making the mixture richer should clear that up, although the root cause of a lean fuel mix might be a dirty carb. Your bike is 13-14 years old, so it's probably due for a good carb cleaning.

However, the dying out part is the troublesome condition. I can't speak to the Sporty, but I know on my other bike, the ignition system was going bad. The bike ran fine while cool/cold. Once it got warmed up, it would backfire and pop under load. Towards the end, once it warmed up, the ignition system would stop working altogether.

I'm not saying this is your issue, but that's my experience. Take it for what it's worth.

 

I'm leaning more towards the ignition system as well, because it runs fine and smooth 90% of the time. How would I go about testing the coil ect?

 

When I test the coil will it give a bad reading when the bike is cool? Or would I need to get it warmed up to the point where it is misfiring in order to for it to show the bad reading?

 

Coils go bad hot.

 

Intake seals

 

Sometimes they "go bad" when hot because resistance builds as the windings get hotter. The increased resistance will usually show up as the misfires/popping, etc...

But there is no requirement to test it hot, the specs given are for a cold coil. Test it cold.

I don't know what the specs are on your coil, but you should be able to find out easily enough.

 

When it is spitting and popping how does it react to an adjustment in the choke/enricher? Just might tell you if the mixture is lean or not. Removing the Carb isn't too much trouble if you need to clean it.

 

A coil can have a break that only opens up when hot.


O4 and later Sportsters have a problem with the Crank Position Sensor, don't know about the 03's.

 

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