Erratic idle in the rain

I found a string from September on a similar issue, but it was old enough and I had a few more questions that I started a new one. I ride year-round in western Washington and have problems with idle in the rain. It runs great when dry and will maintain idle just over 1K with no problem. In the rain, I have to give it a little choke to maintain idle, and have trouble getting it just right. I don’t have any trouble with performance when I am riding in the rain. Throttle is responsive and smooth acceleration, it’s just when I am at idle. Once I pull into the garage, if I let it run for a several minutes, it eventually evens out and will idle without choke again.
The previous string (“Performance in the rain?”) suggested grounding wires. A friend of mine also suggested the same grounding problem yesterday, and another suggested water being drawn into the carbs (cracked boot?) today. I start leaning towards the grounding problem because my idle is fine in dry weather no matter if it is 20 or 90 degrees outside….however, I also know that choking the engine shouldn’t aid combustion for a grounded wire not delivering to the plug. To make it a little more interesting, I don’t recall having the same problem in warm summer rains, just those beautiful Washington 40 degree days give me trouble.
Both explanations seem plausible but neither seems to have “text book” symptoms. My thought process tells me:
If it is a cracked boot, it should also be erratic acceleration and possibly erratic idle regardless of weather. If it is grounded wires, the riding rpms may provide enough “juice” to fire the plugs, but I wouldn’t think the choke would smooth the idle.
It’s never left me stranded, but it is annoying to constantly be managing the choke and idle when it is raining (which does happen from time to time here!). Anyone have input?

 

It sounds like your coils, coil wires, or plug boots may have some small cracks (in the coil cases, the cracks don't have to be very big at all!) that, when moisture infiltrates, causes erratic performance in the spark going to the plugs.

An easy way to test for these problems is to have a COMPLETELY darkened area (nightime, lights off, etc.) and start it up and see if you see any tiny blue or white flashes of light around those areas. If so, you know the culprit.

If that doesn't help pinpoint the problem areas, then out comes the multimeter and you start checking resistance on the coils (both primary and secondary side) and the plug boots. Also visually inspect all components very closely to look for cracks, broken wires, etc. Make sure the plug wires are "screwed" tightly onto the plug-end boots.

Do all those checks while things are dry, and then again when you're having problems (wet) and I'll bet you find your problem!

 

Thanks, Chacal! I'm still confused why the choke would help the problem, but I won't be surprised if I do have a problem with my wires and/or coils since I believe they are original. What do you recommend for running with lights off to check? I assume fuses would be the easiest. Also, woud a spray bottle of water be enough to see the problem without waiting for rain (although I don't usually have to wait long in Washington)?

 

You're very welcome!

Rich mixtures are easier to ignite than lean ones. OR, it may be two separate issues, with the wet mis-fire exaggerating and bringing to the surface the dreaded "clogged bowl starter jets" problem:

http://www.xjbikes.com/Forums/viewtopic ... rt=15.html

I'm not sure what you're asking here???

When I said "with lights off" I was referring to ambient light, such as an overhead light in the garage, etc......but disabling or obscuring the headlight and side lights would be a good idea too.

Should...just make sure you spray from all directions in order to try and mimic "real world" conditions as closely as possible.

 

Thank you again sir. The rich mixture explanation makes sense, as it is still getting enough spark to run, and making it richer might be just enough to help.

You interpreted my poorly worded question correctly about the light. My headlight in the garage adds enough ambient light that I think it would be difficult to see grounding spark. I guess I could also cover the lights with dark cloth.

I will give the spray bottle a try and see if I figure anything out.

 

Puget Sound? Lots of salt in the air? Make electrical problems worse.

 

I suppose if salt water is a likely culprit, cruzing across the sound on the ferry 5 days/week probably doesn't help! :roll:

 

Box the whole thing up and send it here where we don't ride when there is salt in the water

Salt water is an excellent conductor of electricity. If you get dried on salt and then add a bit of water........

You are a definite candidate for packing all the electrical connectors with dielectric grease.