Here it is....I own a 1985 FXSB and never had a problem with it. Rode it in June and all was fine...Came back from Europe and started it up, got about 2 miles down the road and it started to sputter and backfired. Stalled on the way back as if it was out of gas.

I started it back up after about a 1/2 hour (jumped the battery) and drove it home. Stalled in front of the driveway....when it idles it seems to run okay (with the choke slightly out, keeping RPMs at 12.). When it idles it sputters and does not have that same smooth sound it always has. I am thinking it is a gas/carbrator issue as I can keep it running as long as I keep the choke out slightly or the gas idling slightly higher than it usually does. I thought it might be water in the gas but that doesn't sound practical if I can keep it running with the choke out slightly.

Additional stuff tried....sprayed carb with cleaner....took off Air cleaner and cleaned foam filter, rode with it on and off but challenge still exists.....

Ideas????

 

It could be the float valve sticking due to getting sludge from the tank down into the carb. If the float valve sticks open you get gas out the overflow tube. If it sticks closed you run out of gas. It depends upon where the sludge lodges as to whether it sticks open or closed. Shocks, vibrations and fuel flow will dislodge it and wash it down into the bowl where it doesn't really do any harm. It's just passing through the valve that it causes problems.

How did sludge get from the tank into your fuel line? A shredded strainer. The way your shutoff valve works is at the center position it closes the hole fuel flows through. When you set it to normal it opens the hole and raises a tube in the tank and fuel flow into the top of the tube down through the valve. When you set it on reserve if lowers that tube so you can drain from a lower position in the tank. That tube slides up and down inside the strainer. The strainer is that tube, the plastic frame housing it and the plastic mesh surrounding it. That plunger going up and down eventually shreds the mesh. That mesh is keeping sludge out of your fuel lines.

The strainer is suppose to be inspected and replaced as needed every 5k miles. It seems to commonly not get down because you have to drain the tank to do it. So if you haven't done it then there's a good chance it hasn't been done. It's like $15 to replace the strainer and fuel line. If the strainer is letting sludge into the fuel line then the fuel line may have sludge in it as well so you might as well replace it as well.

You can verify that is what is causing the problem by inspecting the float bowl. If you're getting sludge from the tank into the carb then it's going to be at the bottom of the float bowl. Likely it just started and thus the reason you just started having problems so there won't be much, but there shouldn't be any. If you inspect it you might as well clean it so if the problem repeats you can tell whether you just didn't get all the sludge out of the lines the first time or if it's a differant problem. If it repeats whack the bottom of the float bowl with the handle of a screwdriver or something to get the valve unstuck.

It could be something else, but with a 20 year old bike this seems a likely cause.

 

Sounds very logical and relative to the success I have had with the bike over the years, coupled with it running at a higher RPM, I find it hard to believe it is anything beyond the fuel (i.e. mechanical or electrical). I will give it a shot...

 

This might not be the problem. Friend had a 89 springer. The regulator would over charge and pop the circuit breaker and sometimes not reset and the bike would run exactly as you described as the battery voltage dropped. He always believed it was fuel and after a few years of problems replaced the carburetor. Didn't fix it. Luckily I was with him on "one of those days" and when we got to our cabin, borrowed a volt. tester and concluded that the regulator was shot. It would either over charge, under charge, or work correctly. New regulator and now 2 years later no problems.

 

Good points to consider...I emptied and removed the tanks, cleaned the filter and stuff out of the bowl (removed the seat and polished the aluminum heads to chrome with 1000-2000 wet/dry paper + mothers mag polish-focus...) and ran the bike around the neighborhood with new gas...ran a little better (maybe percieved better) but still had a sputter that wouldn't go away and forced me to keep the choke out slightly to keep at 10rpm. This said, battery has been loosing charge and perhaps odd but the flasher for signals suddenly stopped working right. If the voltage regulator is screwed up this would account for the sputtering in the cylinders. Off I go with my voltage tester to investigate....thanks again

 

When the circuit breaker was stuck open before we replaced it, I jumped the terminals and the second the charging system was somewhat working, It idled perfectly. Check the breaker. it should be under the battery box attached to the mud flat. It is normally closed. After that I would like to see 12.6-13 volts at an idle with a good battery. You can also check the stator by unplugging it, AC voltage should be around 15 at idle and run up to about 60-80 when you rev it.