water in fuel after rain

[Lbyvik]

ok guys....HELP ME!!!

I have an '87 K100 RS with about 100k on her.  I ride her daily as part of my commute and on weekends. She runs great generally. 

Here's my issue.   I ride her to work in the morning.  It rains while she's parked and when I go out to ride her home she stutters and bucks and etc...like there was water in her tank or like I put bad fuel in.  Its horrible.

Its happened 3 times.  Riding in the rain seems fine as long as I am moving and started out dry. But once parked and left for a while the symptoms return.

I always have a tank bag on and in rainy weather the cover is over that. So that would rule out water invading the fuel cover.

I've not had the valve cover open in a long while.  I've looked for bad seals and don't really see any, but that means little.

Anyone have ANY ideers?    :dunno2:

[TimTyler]

If you've never done it I'd still suggest replacing the seals in the fuel cap. It's pretty painless and not expensive.

Does the bucking go away after a few miles, once the bike is warmed up?

How many miles on the air filter?

[Scott_]

If you say that the tank lid is covered, I'd doubt that you are getting water in the fuel tank through the tank bag.

Something to try in a low-light(dark) spot, look for stray "spark" around the spark plug wiring while the bike is running. Where the plug wires run along the edge of the head and around the coil packs.
If you don't see anything, then try a "spray bottle" of water and carefully spray some on the plug wires, coils with the bike running and see what happens.

Something else, on a weekend, or day off, get the garden hose out and wet down a specific area at a time as see if you can determine if the rough running happens when a certain area gets wet when cold.

[Lbyvik]

THANKS!!!!  I did the fuel cap thing last summer....those seals are good.  But I hadn't thought about the plug wires! and THEY are Cracked!!!

So thanks Scott!  At least I have somewhere to start and this makes sense. Which is probably why I didn't think about it!  I did the plugs last at 70K miles and I've got nearly 100K now.  So its likely time to do plugs and wiring harness.

[K75RT Keith]

Clean the vent line on the right side of the tank and replace the gaskets on the cap.  Known issue as found on this site, IBMWR and BMWMOA sites.