All 2st Homemade Airbox Drain Valve

I've had a couple instances of drown-outs through moderately deep water crossings with my 2008 CR 125. In both instances, I got water in the carb. The first time, I had the stock carb vent line setup, so I just figured I sucked a little water through the low-hanging vent hoses. The second time, I had Uptite's carb vent filter installed, with a T'ed secondary vent line up in the airbox. So I doubt the water got in that way. I suspect some water got sucked up through the gaping airbox drain port.

I figured some sort of one-way drain valve, like a check valve, would work. That would prevent water going in, but it would let any water out should I REALLY submerge the bike.

My first thought was some sort of aquarium check valve, but Petsmart didn't have anything that would work. Then I thought about something from Home Depot, but decided to just make my own.

Here's what you need:

Children's Tylenol or similar tapered measuring cup
Floating foam or plastic ball (I used a ball from one of those cheapie elastic string paddle ball toys--my son will never miss it)
Safety wire
Silicone or epoxy or JB Weld

First, verify that the cup's diameter, measured at the bottom, is smaller than the ball's diameter.

Cut a large hole in the bottom of the cup so that the ball will seal against the hole.

Put the ball in the cup and run some safety wire to keep the ball from falling out.





You need to use a utility knife to cut a semicircle out of the bottom the airbox so the valve can insert. I used a combination of RTV and some epoxy to block the airbox's drain port and attach the new valve.





I had to trim away some of the bottom of the cup to clear the swingarm at full compression--you should pull the shock and verify that you have clearance. I will also safety wire the valve to either the mudflap or the airbox before I take it for a ride.

I tested the valve in the sink and it works great. It flows plenty of water going out, but not a single air bubble when I submerged it.

Hopefully this works--I'll update after my ride tomorrow--I'm sure I'll be finding water now that all the snow is melted...

that's slick. Reminds me of a shop vac shut-off or kids snorkel.

darn good thinking bud, nice trick.

i've used j-drains and duckbills for boats...same result as yours.

http://www.rexmar.com/page157.html

I "think" you can also use a piece of a $7.00 1" air vac/vent ball check I use on irrigation systems. At least I think it would work. It's baciscally what you built. Way to fab., good job.

My fix doesn't completely seal the bottom hole, but slows water entry waaaay down. I cut a piece of 90 degree plastic from a package that some tie downs came in. Then cut 2 slots to fit the bolts that hold the mud flap on.
Remove the mud flap, install my fix, bolt the mud flap back on, done. It's worked pretty well for 2 years+

I'll take a pic and show it here if it's ok......

Please, post up your fix!

First I looked around the shop for something that would work and found a plastic holder package for tie downs.(1st pic)
Then I cut out a piece that would fit behind the mudflap, use the same bolts and mostly block the hole. (pic 2&3)
Pic 4 is a crappy pic of it on the bike.
It slides in between the edges at either side of the hole (pic 5)