Bike about died in rain......

[Redman]

............ power washing my engine in NM and no problems with restart.............

I am reluctant to take bike to spray-it-yourself-car-wash, but have. But do try to avoid bearings and ignition and instruments. Have not had a problem after such washes.

But this occassion was about 10 miles in rain, then 15 miles in downpour (water falling so hard that just the water between the fairing and my faceshield cracked open abit was running across my face and down my neck) and then another 30-40 miles on wett pavement. That did it, after a rest stop it barley started, and stumbled fora couple minutes.

[Tom R]

I rode without that gasket in a rainstorm and experienced pretty much the same symptoms. I since cut one out of something I had in my garage, don’t remember what, but haven’t had the issue since. Btw - I had only one or two year old plug caps on at the time. I’ve ridden in the rain more that I’d have liked to, and it was the only time my bike ran weird.

[DRB166]

I'm mostly a DIY guy, but outdated on bikes. I used to use a lot of RTV. On covers, connections, anything that could stop the bike. Also, dielectric grease, in a tube (not dielectric paste) for every electrical connection. I never had any problems. Is this a possible solution?

[Redman]

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Darkend the garage and Did the spray-salt-water test. Could not recreate the the stumble-bumble. Could not find any errant sparking. Sprayed most the entire bottle of water all over the wires and the coils and the plugs until I was choking on the steam and the exhaust.

But then went about changing the ignition cover gasket. Then noticed, hey, look at that, can see gasket material sticking out all the way around, I dont recall that from before.

And then went about changing out the 4 four spark plug caps.
Earlier this summer I ohm check all four and all were the 5k ohm.
Now I noticed that one boot at the wire was cracked/split, and I noticed that 3 of the four had the boot at the plug that was quite stiff and the opening for the plug was a lot bigger than the new ones. I also noticed that the paint in the lettering on 3 of the four was faded almost gone.

I also pulled the wires out from the bike frame to inspect and to clean/treat with WD40.

So I replaced the four caps, Thinking that maybe the rubber boots could possibly contribute to the poor running in the rain, but not really convinced.

THen later took another look at my existing caps - inside the caps - OH!

Looks like some sort of deposits in three of them - OH!
I suppose that can lead to a problem especailly if gets wett in there.
As first I was thinking some sort of rust deposits. But cant think of what is in there that can rust.
I suspect maybe is the result of some arcing.

(I had a 65 Mustang that would get stuff like that in the distributor cap and then run poorly.)

Okay, now I think I have found something related to the problem of running bad in the rain.

[Cipher]

use a screwdriver to take out the brass bits. There is a resistor and a spring inside,

[Redman]

use a screwdriver to take out the brass bits. There is a resistor and a spring inside,

Yep. Ohm check was good, so wasn't concerned about the resistor.
I was looking for what might cause poor running in heavy rain.

.

[Cipher]

Oh my do check at least one. You might find the spring all rusted. Its a 5 second operation.
The points cover is odd mine has no gasket and theres never been a problem.

[Grimly]

I am reluctant to take bike to spray-it-yourself-car-wash, but have. But do try to avoid bearings and ignition and instruments. Have not had a problem after such washes.

But this occassion was about 10 miles in rain, then 15 miles in downpour (water falling so hard that just the water between the fairing and my faceshield cracked open abit was running across my face and down my neck) and then another 30-40 miles on wett pavement. That did it, after a rest stop it barley started, and stumbled fora couple minutes.

Yep, that will do it. That's absolutely classic signs of fine spray droplets getting up into places they wouldn't normally reach and if it goes on for long enough, they soak components that would normally dry out almost as quick as they got damp. Engine heat really plays a large part in this. It's easy to think the coils are well up out of the way, but spray gets everywhere, even under a fairing.
All you can do is thoroughly damp-proof the coils and connections up the top and you might even put a simple plastic shield around them (nothing more sophisticated than clingfilm does the job). Of course, by this time elderly HT leads are prone to damp misfiring, so they need replaced anyway, just to be on the safe side - they've reached their disposable age by now. Plug caps and all their boots need replaced, too.
As you're doing the LT side down at the triggers, also make sure any LT wiring connections are clean, tight, and waterproof.

[argonsagas]

As did others, my first thoughts went to plugs and wires, however the symptoms described could result from a bit of water in the gas....

You might check the gasket fitting on the tank cao, as water just MIGHT have crept inside

The longest single trip my GK saw in rain was roughly 150 miles of non-stop rain, varying from mild to heavy, with the final twenty in downpour.....

.......then I had to turn around and go back

The return trip saw a little less rain, but the GK never gave a hint of a problem.

[850 Combat]

I agree with everyone who put it on the high voltage side of the ignition. I had a Guzzi 850 Eldorado, It had a Bosch charging system with a belt driven generator on the top of the motor, and it had an automotive type distributor on the top upper side of the crank case out in the weather. It would get wet and short out on the low voltage side. Fortunately, it only did it to me twice. Both times, I was on the way home from a longish day trip, and it died in front of a pub. Burger and the rain stopped. Guzzi goes!