WTF is wrong with my bike?

[guitar man]

OK, this is weird. My little 99 Sportster has been ultra reliable up until the last week or so.

I can start it up in the morning, cold, ride for about 100 miles or so with no problem and then it pops, farts and dies. I can let it sit and cool for 15-30 min and it starts up and I ride off like nothing is wrong.

On the way in to work this morning, it quit about 75 miles into the trip, which is a bit shorter distance than the previous episodes. I was able to determine this morning that when it dies, it is from losing spark. I pulled the codes and it hasn't thrown any trouble codes at all, so I'm stumped as to what the problem is.

I'd appreciate any advice anyone can give me

thanks :)

[JustABozoOnThisBus]

1. Hmmm, you say it's the spark

how can you tell? Pull the wire, crank it over, and if you don't feel tased ...?
That's my test, and if it's got spark, it hurts.
:rofl:

The first thing that occurred to me was "vapor lock". Is the engine running hotter than usual, enough to boil the gas in the line or carb bowl (I don't know if that bike has a carb)? Has it done this with just the current tank of gas, or with several?

100 mile commute? Yikes.

:hi:

[guitar man]

2. that was my first thought

I thought it was vapor locking too at first. It started acting up when it got hot and humid here this year. The first few times it crapped out, by the time I got the tools out of the bag and started trying to find out what was going on, it would start again. This morning I managed to get the rear plug out and crank it over very soon after it died. No spark. :(

It was 68 degrees this morning and I was running 4 lane at 70-75mph, I can't imagine it getting hot enough to vapor lock under those conditions.

thanks for the response :hi:

[JustABozoOnThisBus]

3. My second guess is "coil"

But I don't know anything about '99 Sportsters. Does it have a coil? If so, do you have a friend with a similar bike to exchange coils with? Then, if the problem jumps to the other bike, you know to buy a coil. I'd hate to replace a good coil with a new good coil, that's a waste of money.

[guitar man]

4. I was just thinking that too

I was mulling over what might get hot and cut off the spark and the coil kept coming to mind. I like the idea of swapping coils to find out if that's it rather than shelling out bucks for a part I might not need. I think most of these Harleys use the same coil if I remember right

thanks

[HamstersFromHell]

5. My first guess would be coil

Known to fail from heat stress.

Old ex-coworker I hadn't seen in decades brought his Harley to the last shop I worked at in TN because he was fed up with the dealer. Dealer replaced both the trigger and the black box trying to cure his random "get it good and warm and it dies". Fired it up, ran 5 minutes and dead. Changed coil, all was good. Always check the cheapest (and most common) solution first before you let a dealer run profit margins on you!

Likewise, the most likely cause of "no electric start" on modern (Evos and later) Harleys isn't the solenoid, but the little Bosch starter relay. Harley charges $19 for it. Buy it at the auto parts store (or even a halfway decent car stereo shop...they use 'em in alarm systems) for under $6.

[guitar man]

7. thanks for the reply

I'm hearing coil from more and more people I talk to, so I think I'm about to change it out and see if that cures it. Harley Dealer wants $152.00 for one, JP Cycles has one for $40. I'm going to call a local independent shop here after they open up at 10am and see what they want for one.

thanks for the help :hi:

[ThomWV]

6. Question

Ok, you fire it up and ride, then after a while it farts and dies, then you wait 15 minutes and it restarts and runs fine. Now tell me, after it quits the first time will it die if you ride it for another hour or so or does it keep on running the rest of the day after it dies the first time.

Also, how many times has it done this? Is it every trip of length, or just sometimes?

On edit: I want you to go check you negative battery cable's connections on both ends - don't just make sure they are tight, make sure they are Clean and tight.

[guitar man]

8. thanks for replying

I could have been more detailed in my OP. :blush:

After it dies initially, the longer I let it cool off, the longer I can ride. After it died yesterday morning,I let it cool about 10-15 min and rode the last 20 miles into work. I heard it pop like it was about to quit right as I pulled into the parking lot.

I just went out and checked the battery cables, they're both clean and tight at both ends. I thought they would be, I had just cleaned them about a month ago and after the bike dies, the starter will spin the engine like a windmill, it just won't start :(

[guitar man]

9. update

I found a coil for $67 at a local shop and installed it during lunch. I took the bike for a spin and it runs a lot smoother than it was and seems to be making more power. I guess I'll find out if that was the problem when I ride home to Tulsa this weekend.

Thanks everybody for all the help :hi:

[guitar man]

10. Bingo!!

that was it, rode it home to Tulsa Thursday night, 100 miles and it ran like a champ, didn't die and started right up after I shut it off. It was the coil. Thanks for all the replies and help. :hi: