Shutdown in the rain

[toomuchstuff]

I know that i will have to do some digging on my own, I'm wondering where folks would start looking.
Wife and I took a ride around Nova Scotia this summer for a week, which of course meant some rain. The machines were a late '80 and an early '81, so identical specs. Both ran great in dry weather or light rain, but when riding in moderate to heavy rain foe an hour or more both bikes would stall and not re-start when slowing to an idle. As long as the revs were above 2500, no issues in the rain. The first time they stalled we were stopping to check the map. Both bikes quit within seconds of each other. After about 90 looong minutes, they re-started. I bumped the idle speeds and that got us through the remainder of the day. The next rainy day, after an hour of riding in heavy rain, at the 1st traffic light both bikes retired for the day. The next day, after drying out, both ran like nothing had happened.
My initial thoughts are looking at the coils, but the unit I have looked at, seems sealed up properly. Also, plug caps were new and well sealed. Next thought is the ignition box?
Any thoughts would be appreciated.

 

[Jan_P]

If they shut down on both sides .. No misfiring .. just dies
I would check Kill switch first .
And then power wire to Coil service the connectors

But this one can be difficult I believe Voltage is dropping because of a partial ground .when wet
And getting to low for ignition to work But can be anywhere .

Brush inspection and checking charging when dry across battery Is always good to do and simple

If difficult to find I would consider to make new wires to the ignition and coil outside the harness.

 

[gggGary]

Were the air filters dry?

 

[Jim]

I've read that some Yamaha 4's of that era would do the same in the rain... early TCI (not unlike these) ignition. It's not sealed against moisture, so the circuit board can get wet. Never heard of these bikes doing that, but it's the same basic design on both TCI boxes.

 

[jpdevol]

I've got a long-shot that'll give similar symptom: significant dirt accumulated in the carb vent tubes, when it gets really wet it turns to mud and blocks the vent. Had it happen on an old 750Four(albeit the vent tubes routed below the swingarm and collected a lot of rear wheel dirt

 

[toomuchstuff]

Thanks for the suggestions. Both bikes were charging fine. (Voltmeters on both) I didn't check the air filters but 1 runs pods and the other is stock with good filters. I could see the pods getting soaked but I don't see how that much water could infiltrate the stock filters. Something to test further. TCI box is one of my suspects. It may be time to have them re-built and look at a better way to enclose them without creating a heat problem.

 

[Jan_P]

Strange that 2 x bikes stalls at the same time
I have no experience of the stock TCI
Points and Boyer .usually some misfiring or running on one cylinder
Any chance filling up at the same place getting some strange chemical ..as water included
Ethanol fuel ??

 

[nj1639]

On my converted to TCI '77, I first had the module setting atop the forward part of the battery under the seat. Now with unipods it's located aside the battery box, left side of bike under the side cover, mounted using the threaded hole left from removing the stock air box. Heat nor rain has affected it.
Having them stock mounted under the battery box makes them a real pita to get to.

 

[toomuchstuff]

Again, thank you for the responses. I eliminated bad gas as a possibility. Also it is not plugged carbs. Fuel system seems fine. The plan moving forward is to check and waterproof the coils, clean and dielectric grease all connectors and possibly get the TCI boxes overhauled. At this point in the riding season, I don't anticipate having final results till next summer. I'm not about to test in a cold October New England rain. I'll post if I find a "smoking gun" but otherwise it will be a thorough maintenance cycle. Thanks again for the suggestions.

 

[jetmechmarty]

clean and dielectric grease all connectors

Be careful with that. Dielectric grease is not conductive. I myself only use a smidgeon on spark plug boots, and none anywhere else. Deoxit for electrical connections. I know plenty of people disagree with me, but... YMMV.