[woolerguy]

Hey guys,
I have a 1990 TRX300 fourtrax 2x4. This spring I noticed I am getting water into the crankcase. Water was very shallow. Under 10 inches deep. Maybe just over the foot pegs. The only thing I see where it may be coming from is the crankcase vent tube. The tube comes off of the crankcase and goes to a plastic tee. From there a line runs along the frame up to just underneath the top of gas tank. The other tube drops straight down towards ground. At the end of the downward tube is flap of rubber material. There is no valve or anything. Is it possible water can get sucked back up this tube to crankcase? I'm tempted to run a single vent line from crankcase up to gas tank and eliminate the line going to the ground. Any ideas or suggestions?
Thanks

 

[SamUK]

It’s very possible to get water in through said hose/pipe. You have two choices really, block off the lower hose or route a new hose higher up the frame near the Air intake, don’t put it directly next to the inlet of the air intake though, leave a few inches.
Either of the above options won’t harm your engine in any way whatsoever.

 

[woolerguy]

I have owned the bike since 1993. This is the first year for this issue. I checked the hose for cracks or breaks and there does not appear to be any. What do you think would cause the water now getting into crankcase through the lower line? Also what's the purpose of the main vent line being divided into 2 separate lines with one going up and the other going down? Is the lower one maybe for drainage in case crankcase gets flooded with water through main air intake? If that's the case, it should have a check valve. I wonder if the flap of rubber is supposed to act as a check valve. It looks like the flap you would see on one of those fart cushions!!

 

[SamUK]

I have owned the bike since 1993. This is the first year for this issue. I checked the hose for cracks or breaks and there does not appear to be any. What do you think would cause the water now getting into crankcase through the lower line? Also what's the purpose of the main vent line being divided into 2 separate lines with one going up and the other going down? Is the lower one maybe for drainage in case crankcase gets flooded with water through main air intake? If that's the case, it should have a check valve. I wonder if the flap of rubber is supposed to act as a check valve. It looks like the flap you would see on one of those fart cushions!!

That’s exactly the valves purpose. I love your ‘fart cushion’ description though, that made me chuckle!
I’d say the check valve has just distorted over time or perished. I really routed a new hose on my 300 as it’s a mud bike, I just didn’t trust the check valve.
If I still have my OEM check valve I will ship it to you, I can’t guarantee it works though as it was one of the first things I removed before dunking my bike in deep water.

 

[RemMax]

The crankcase should be under light positive pressure when running so it can't really"suck" water in it
BUT.... If the water pressure gets higher than crank pressure it will get back in

I've been lucky as I've never had water get in my engine, just the diff's ?

 

[woolerguy]

Thank you for the offer of the OEM valve, but I think I may just run a single vent line up the side of frame. I would never on purpose have it in water high enough to reach main air intake. If it happened by accident, I certainly wouldn't leave it running long enough to cause any pressure build up in crankcase anyways.

 

[fishfiles]

....on the end of the vent tube you should find a duck bill looking thingie , I think the real name might be a vacuactor or something like that , do a way with it and the tee , run one vent line up as high as you can possible get it with or without a snorkel , or into the air box with a rubber grommet , 3M5200 , silicone or such