Any hints on figuring out why my bike died in the rain yesterday? It ran perfect today so seems to have fixed itself. I have an FXR with an Ultima 107 and Mikun 42 carb (with tilted front chrome cover).

Although I had ridden through a light shower about 30 minutes prior, a seriously heavy downpour saw the bike sputter, cough and stall. The electricals remained on and she started straight back up, but I spent 20 mins (tring to get home) with the bike sputtering and coughing along. The oil pressure gauge indicated standard oil pressure and my electricals were not cutting out (my digital gauge flickers if there is a short etc). After 20 mins the bike resumed normal operations for 10 mins, until I went to lower gears pulling in to home, when she sputtered again. I let her idle a bit and shut her down. Took her for a run today and zero trouble, back to normal.

The air filter was soaked yesterday when I took the cover off to check. Could water in the carb have screwed it up?

 

If you get caught in the rain and the air filter gets too wet/soaked, It will start sucking in rain instead of air and it will start spitting/sputtering. The carb is meant to suck in air, not rain/water, so since it cant burn the rain/water it starts spitting/sputtering.

 

coil is bad

 

Well it could be a bad coil like Dave said, way to test it is with a garden hose while the bike is running.
if that does nothing the problem is the bike is injecting water in the carb.
if it is dying then you are getting enough water so the spark is not igniting the gas, if the bike does not die and idles ok just does not want to accelerate and runs real rough under load the the MAP sensor inside the intake is getting wet and the bike is not retarding the spark under load.
This is a pretty common problem.
How old is the bike?

 

Harleycruiser, the bike died and would not idle properly. I started her up but she would not idle, so I had to keep her in 2nd or 3rd and sputter along with her surging and coughing. After 10 mins she stated running fine again.

The Ultima 107 has about 12,000 km on her, so no old. But the FXR is a 1992. I have replaced most original stuff, charging and ignition system included. Not sure if all that answers your questions.

Aquadave, not sure about the coil. It's less than 2 years old and I don't have any starting, charging or other electrical-related issues. I'll spray it with water while idling though and see.

Mainly I am trying to determine if this death by rain was an isolated, freak thing (it was torrential), or an indicator of a problem waiting to happen.

All suggestions welcome.

 

If this only happened once, it's probably just the rain. If it was something else, it would be
failing most of the time. Don't make something out of nothing.

 

Well like I said I would spray the coil with water same with any electrical parts, and connections, and see if you can replicate the problem.
we do not have the problem with cracked coils like we used to due to better housings, but easy to check.
I would also suggest dielectric grease in all connections if you haven't done so.
This keeps the contacts from corroding and helps keep water out.
This should be done on a regular basis, every three to five years, or any time they are taken apart.
I am with ragtop if this was a one time occurrence I would not worry about it unless you plan on riding in the rain more often, then you might want to consider something to cover your air cleaner like a cut up two liter bottle over the end.