hello my name is Siez i am writing you guys in hope that some one can help me how to solve a situation !! here is the point, i have a 1999 sportster883 with a s&s carb , i have it for 15 years with this set up and i never have a single problem,she was working just fine 2 weeks ago ,and now i tried to start the bike and she just crank the engines and backfires from one cylinder and won't start!!! i have gas on the bike!! what could it be guys?? HELP PLEASE!! thanks

 

First thing I'd do is pull the plugs and see what they look like; if they have black crud on them, would indicate a non-electrical problem. Plugs look ok, crank the motor while they're out, holding one at a time against bare metal (not with bare fingers!) and see if both are sparking. Then stick a finger over the plug hole and see if both cylinders have similar compression. A compression gage would be better of course, if you have one.

Check to see that none of your buddies swapped the plug wires (I've seen that!). A crankshaft position sensor (easy to reach, next to the oil filter) could do that if it went bad. Not sure if a bad ignition control module would do that... maybe. those parts are hard to troubleshoot, almost have to plug in a new one to tell if they're bad.

I don't know if your S&S carb has a bowl drain, might have to pull the bowl to check for water; get some gas with a little water in it, that can keep it from firing up. Wouldn't think it would make it backfire from one cylinder, though.

Can be tough to diagnose electrical problems. Let us know what you try, and someone else might think of something else. Good luck with it.

 

idk about bikes, but with a car id be doing a compression and leak down test. Typically in a car when the intake valves are leaking or not sealing they will pop through the intake

 

i purchased a 95 883 bout a month ago for 1,500dlrs from a guy who had same problems i got it home checked for spark and very little to nothing but bike had compression and good battery pulled plug wires and they was rusted new plugs and wires and coil it fired right up also check the plug gaps mine was set at .30 so i reset to .40

 

I would be willing to guess that you have a bunch of water in the gas tank or a timing issue...you can figure out how to fix the first..for the second I would pull the timing cover (small cover on engine by right foot, you may have to drill out the rivets on the cover) and take a look in there, I have seen all sorts of issues in there, such as rust and corrosion, to the timing sensor (bell) breaking loose ...

 

Pull your plugs. That's the

first step.