1991 Sportster wont start backfires

I have a 1991 Sportster 1200 that backfires when I try to start it. Here is what happened:

I started it I was on my way to work drove about 15 miles everything is fine at this point I had to to turn it to reserve as I always do (little peanut tank) I pull into the Shell station fill it up, turn the peacock back to on take off for the rest of my ride to work everything is fine for 6 miles then I get behind this car going a little slow so I crack the throttle and pass the car about a mile later I could fell the bike surging a little, then a little worse, then a lot worse then it was dead. So I get it home it is getting plenty of fuel so I pull the spark plugs put in new ones try to start it and every so often it back fires. I'm leaning toward a trimming issue but don't know what to look for. Can someone please help me with some ideas.

Thanks
Thumbless

I would pull the carb cover off and take a look at the slide diaphragm (rubber boot) first.

Carb just had a complete rebuild this spring.

It's the plug coming from your stator. It's either loose or came unplugged and your battery is not getting a charge. Exact same thing happened to me a few times till I just changed the plug out on my 90 883. It should be located under your transmission. Have you checked to see if your battery has a good charge?

Batter does have good charge. I'm new to harleys is the stator on the left or the right side.

I think as of 91 they moved them back out from behind the clutch basket and onto the front engine spindle. Do you have a manual for the bike? It should show a picture of the plug I'm talking about. If not, then a J&P catalog should show it to you. I swear, it sounds like your battery is dying. Mine would backfire when the charge went low because that darn plug kept coming loose.

Always got me home though haha. Surprised I didn't wind up with a piston n my pants the last time it got so rough and backfiring the way it was by the time I pulled up to the garage.

Well when it died it was still turning over good until I run the battery dead trying to start it and it was still backfiring after I charged the battery.

I could be wrong then. The symptoms do sound exactly the same though. When mine was that low, it wouldn't turn over well anymore. If I was lucky [most times I was] it would fire just before going dead.

It only backfires and doesn't start?? Or runs and backfires occasionally?? If it doesn't start,check for spark...stick the plug in the boot and ground it against the head bolt.....should have a bright blue spark....Fuel, timed spark and compression it should fire up...Factory Service Manual and Parts catalog will pay for themselves first time you use them

Then on the way home, is when the backfiring would happen from the battery going dead because the stator wasn't hooked up anymore, from the plug being loose.

Mine only backfires and never starts, I checked for the spark, while it does have spark it is intermittent which is why I was leaning toward a timing issue.

Check the condition of the plug wires, make sure the ignition module ground wire is clean and tight,could also be the coil or pick up sensor...

When I pulled the seat off I found this, I plugged it back in but I still have intermittent fire and seems to be worse now.

Yes all the wires seem to be fine tight and clean, not to sure where the stator is on this bike. Don't know what VOES is I can snap a picture of it. Charging the battery again as we speak.

Will a stator cause a firing issue?

Looks like the ignition module plug...If that was unplugged how the heck did you get any spark?? Oh,yeah....there isn't a separate ground wire for the module since yours has the plug my '90 BT was wired direct(no plug in) your module ground would be in that plug...
Clean both ends of the plug and check for broken wires,could be dirt or corrosion....you'll have to get some slack in those cables too so they won't try to pull apart...

If the spark is intermittent, start with the ignition. Usually a bad pick-up will fire again when it cools down, but not always. also, check your coil, it should have about 3 ohms primary resistance, and obviously check all the wiring and grounds. Don't forget to look for wires or electrical connections shorting out by contacting bolts or metal, or pinched wires. sometimes the chrome covers that everybody likes to add shift a little and will ground something out. Good- luck.

Stator is part of your alternator...if that's bad your battery will slowly discharge while riding...

There are tests for that...I'd suggest getting the Service Manual and a multimeter and run some tests on your ignition system(and stator)...still could be bad plug wires,coil or pick up too...

There is only one proper way to find out whats going on here . You must start with the basics in this order fuel ! Spark and even compression . Now take a fuel sample to start with . Pull the hose from the pep **** open it do we have good fuel flow ? And what does the fuel look like smell like is it gas orf diesel or ethanol ? Is the spark constant and blue? At both plugs? And what is the cylinder pressures? Then we can fijx this bike correctly . Till then we are all pissing inthe wind . More info please!

Yep...He mentioned he has good fuel flow and has intermittent spark...