bike runs poorly in the rain

[Full_Throttle]

Before I go and start tearing into things, I want all of your opinions on what to look for.
'98 Valk that I have owned for 3 weeks.  30,000 miles.  Previous owner hadn't ridden it this year due to bad back.
The bike runs fine.  It starts right up, I need to give it some choke and let it warm up for a minute or so then no choke is necessary.  It runs and drives fine all day.  However, the other day I got caught in the rain for approx 5 miles and she started sputtering and missing as I was going along.  Today I decided to spray it down at the car wash.  Mind you I didn't go "crazy" with high pressure around the engine or rear tire.  I only used high pressure on the windshield and front fender area.  When I was finished the bike wouldn't start immediately.  It would start, but then die upon ANY throttle.  I let it idle while I toweled off the chrome and such.  in the time I spent drying the bike, it cleared up and I was able to leave the car wash.

So where should I look to discover why water is affecting the drive-ability of my bike?  Is this a carb issue or a spark issue?  I suspect Spark, but since I am at work and can't look until this evening I get to speculate all day

What has all of this forum's vast knowledge and experience have to say on the matter?

Thanks in advance,
Mike
 

[sugerbear]

vent tube from the tank.
there should be a "T" in the line somewhere.
either the t is missing, letting the tube suck water in or theres a small kink in the tube.
look under the bike should be a "opaque" colored thingy connected to a tube hanging down.
take it off and drain the drool out. then check the line all the way to the tank.
if there's no T in the line, thats the problem.

p.s. may involve taking the tank off.

after rereading your post not so sure now
my thought was just about the riding in the rain, the car wash i'm not sure about.

[Robert]

Sounds more like the spark plug wires are getting wet and then drying out. There is a resistor in the end that connects to the spark plug more than likely the water is getting to this resistor and causing the bike not to start. Easy check just wet the boots that go to the spark plugs if it doesn't start or runs bad you got it.

[Thunderbolt]

Some have found that shortening the lower portion of the vent below the "T" solves the problem.  It exits the tank on the rear and if I remember correctly, it exits at the sidestand and is held in place by a small metal clamp.

[RLD]

Mine would actually starve when riding in the rain. If I opened the gas cap, it ran fine for awhile, then starve again. I cut about an inch off the vent tube, end of problem, and I did have the "T" in the line. Seems to create a weird vacuum problem when left stock on some bikes. Probably has nothing to do with the car wash symptoms though.

[Tx Bohemian]

I bought my bike last Oct and washed it (at home) for the first time in April.  Ran like crap after that.

One member suggested to check the drain holes in the head where the sparkplugs are.  If they're plugged up water will stand and probably short out the plugs.  Two of my six were plugged.

Although it runs better after the unplugging and draining gas and adding B12 and all that stuff I still think I have a carb/lean problem.  Maybe it was like this before but now I'm more tuned into it, don't know.

It needs a washing again but I'm a little leary now.

[Blister]

Well I try not to ride in the rain anymore as I did that for years using motorcycles for getting to work here in Wa.St. The same thing happened to me awhile back just when I rode into a little sprinkle. I ended up doing a petcock rebuild ( checked it when I pulled the tank to check air filter and found a hole in the diaphram). However you'll notice when you work the air filter cover off it's fairly tight in there. The previous owner hadn't got the lid on all the way and when I pulled the air cleaner out the front half was caked with mud. I'm not sure if the sprinkle had anything to do with it. Cleaned air filter really made a difference, I'd start there and just as well pull the petcock apart as I did to check the diaphram while you got the tank off. You can either hook a vaccum gauge to it or seperate it and hold the diaphram up to a light in a dark room and look around the nipple in the middle for light. Sorry I went on so long. Good luck.