He's trailering it over here tomorrow....needs help fingering out electrical problem.

Bike will be running fine, then backfire and die.....let bike sit a day and it will start and run fine....then going down the road later it will do it again....really hard to restart if it will start at all once it happens.

Bike stock except for custom tank 2 years ago.

Tried new coils already.

Anyone here run into this?

 

sounds like someones gettin free beer!

 

check for spark, check for gas (at plugs) if it has those it has to do something. if it does not have those (for example no spark when the problem occurs) find out why. Backfire seems to imply lean condition (leaf in gas tank?)

 

Yep,

I'm thinking backfire occurs due to interruption in ignition spark.....I don't at this time think the backfire actually causes the failure....From his description, the bike pulls hard when it's running, so I doubt it's starving for fuel.

First thing I'm going to check is his keyring...if he's got lots of keys on it, then I'll examine his ignition switch and see if the heavy keys swinging off it has weakened the contacts....I've seen that happen with cars when the gals lump weighty junk on their key chain.

 

Number ONE...check his VOES sensor...it could be screwy.
Number TWO...make sure the fuel filter (screen on petcock), lines, and carburetor don't have any crap stuck in em.

AAAAAAAAAAnd number three...tune his carburetor again. Also check to ensure there are no vaccuum leaks.

 

I had a similar problem a long time ago, you might want to take off that tank and empty it and make sure nothing is covering the fuel outlet. I had a tank that someone had squeezed a tin cap lid, the kind that seals up octane booster that you peel off before usage, down into the tank and it would get sucked onto the hole and shut the gas off. It would sit for awhile and start and run for a few miles until it happened again. I would be about anything it is something like that.

 

VOES?....I had to look it up....Vac Op Elec Sens.....Ok, that's a good suggestion.

I'll also make sure to remove the gas tank and all supply lines if nothing else works.

Thanks, gents....Keep it coming!

I love this forum and the fact I get to spend my day tinkering on Harleys.

 

Yep, VOES is the bane of my existence....little f*cker always comes loose on me. i hate it.

 

Got any more details? Does the problem happen after a certain amount of time after the bike is running.......like does it die out after like 10 or 15 minutes always? Or is it die out kind of randomly. As for the VOES, i don't think that will be your problem......The Voes won't keep the bike from running, it'll just make it run like crap if it's not operating properly, although if the vacuum line for the voes is damaged the carb can die out at idle from the vacuum leak, although it most likely would be a constant problem then, and wouldn't let the bike run ok for a few minutes and then die. A few things I would check are fuel tank vapor lock, since you mentioned a custom tank, I've seen quite a few custom gas caps that are only vented by a tiny pinhole, that can clog up over time, and if this happens it'll cause a vapor lock in the tank and won't allow fuel to flow. It's simple to test this, when the bike dies, open the gas cap, and try to restart the bike. Another posibility is a failing timing sensor, usually being heat related, and can be tested by popping off the timing cover and using a hair dryer to warm it up. I had an issue with my plug wires arcing last summer through the spark plug boot to the base of the spark plug, took me 2 weeks to figure it out since i couldn't see the arcing under the boot, but once I caught it I put new boots on and it was good to go. Anyhow, it's hard to say based on what you know about the problem so far, but start with the simplest things first. A basic carb cleaning and fuel line check are fairly simple to do, and may be a good place to start to eliminate fuel related issues, then you can work into the electrical. But whatever you do, don't buy new electrical parts unless you know that it's the problem. I always see people that think they need a new ignition just to blow all the money, and end up with the same problem and and not being able to return the part since many shops don't take returns on electrical components. Anyhow, best of luck, let us know if you get anything figured out, or have more info for us to help ya out with.

 

+1 The first and easiest to check for is the tank not venting. When the motor stalls, remove the gas cap and the motor should restart if that's the problem.