Issues after Riding in rain

[Marcusx]

Hey!

I've been following the forum for a while now after picking up my first bike a few months ago( 1980 xs400) and have found this site really helpful for someone new to bikes. The bike ended up spending alot of time with the mechanic to get it running properly but eventually got it back and was running perfect for a month up until last week. It was the first time I had rode in the rain( it was coming down pretty good) ran fine for about 12km then started to bog down, backfire and dropping to one cylinder. The next morning it was intermittently doing the same thing the first 10km then seemed to clean up fine after and rode another 20km no issues and the day after that happened a few more times. Took it out riding a couple times since and haven't had any issues at all and seems to be running fine again.

It seems to have only started after riding in the rain and was wondering if anyone has any advice for what might be causing it since I will have some time to play with it over the winter. I was looking over the bike yesterday and just noticed the Crankcase breather tube disconnected where it attaches to the airbox and wasnt sure if that might have been causing an issue. Would there be any reason the mechanic would have detached it on purpose to vent outside the boxes? Any input would be greatly appreciated

Thanks!

Just some info about the bike:
-rejetted to work with airboxes/chopped exhaust ,carbs cleaned, diaphragm replaced, slide needle replaced to match(bike had 2 different ones on it causing some issues), some rewiring done with new LED tail lights,and installed all in one rectifier/regulator,
-gas cap gasket is completely dried and cracked(not sure if that is letting moisture in)
-unwrapped and checked exhaust for holes and it was all good
-original airboxes

 

[Marcusx]

forgot to mention the night I was riding in the rain was after having towed it for 6 hours in case that might for what ever reason might have contributed to it riding funky for a few days.

 

[OleDoc]

Fuses get wet?

 

[xschris]

Water can be getting it the vent hose if it was not attached. Any pics of the bike?

 

[OleDoc]

How are the plug wires?

 

[willem]

the crankcase breather tube should be connected. It puts any fumes from the crankcase into the air intake, which is good for the environment (no dirty oily fumes into the atmosphere) and good for the bike; it's basically free fuel and it also keeps everything inside the carbs lubed up a little.

Water into the crankcase is bad. Check your oil level! if it's overfilled or you see white drops inside, drain it entirely and replace the oil. You don't want water in there.

Water in your gas tank could also be an issue. It will have gone into your carb's fuel bowls, so drain those using the drain screws and collect what comes out. If you see water in what comes out, drain your fuel tank entirely and fill up with fresh gas.

Other than that it could be the the plug wires or caps, the coils, or anything else electrical. Try replacing the plugs, measure the resistance of the caps, wires and coil as per manual,and feel around a little while the bike is running. If all is good you shouldn't get any electric shocks anywhere

 

[Scorpio1963]

Might seem crazy but take a blow dryer and dry out everything that possibly gets wet when it rains.
Also on my bike I had changed the plugs and even though they were new the bike started running on one cylinder.I checked the spark on each side and found out one of the plugs wasn't firing.
This and listen to willem

 

[Unkle Crusty]

Most often it is water in the plug caps. Remove and dry them, and spray with a water repellent. Good plan to buy new caps, and shorten the plug wyres about 1/8".

Unkle Crusty*