TRX 250 carb questions

[C-mo]

I have a 2001 Honda TRX 250. it starts, idles, & runs fine, except when riding up a steep incline. The wheeler dies on inclines. I believe I have isolated the problem to a rubber tube that comes out the left side of the carb, snakes along the right side of the wheeler, and goes through a clip mounted on the high part of the right side of the frame. The tube is open on the end opposite the carb.

I have twice removed the tube and noticed blockage. Once I clean the tube and drain the carb, the wheeler stops dying on inclines.

I have the following questions:

1. Did the wheeler come from the factory with an open carb vent tube (I bought the wheeler used)?

2. Is it OK to put a check valve on the tube, to prevent dirt, water, etc, from getting to the carb? If so, does the carb suck air in the tube, or blow air out of the tube?

3. Is it OK to re-route the tube from the front frame to drop next to the gas overflow tube that hangs directly from the bottom of the carb?

4. Any other suggestions? -- answers greatly appreciated.

[GPracer2500]

Is it a TRX250EX or a TRX250 (Rincon)? Probably doesn't matter because either of those carbs do have a vent line that routes to open air. It doesn't really suck or blow (much). It just allows the air space above the fuel level in the float bowl to remain at the same air pressure as the outside environment. Carburetors function based on the differential pressure between the float bowl (ambient pressure) and the comparatively low pressure inside a carb's venturi.

Frequently, these types of vent lines also serve as a fuel overflow if the float gets stuck open. The same path air takes to equalize the float bowl pressure with the outside air pressure also provides a path for fuel to escape if the float bowl were to fill up with fuel and then keep filling.

I would try re-routing the line to a "cleaner" place first. It does not have to vent anywhere special. However, don't loop the line back on itself anywhere. If fuel gets into the vent line it needs to be able to drain out the end or back down into the carb. Don't allow a space where fuel could collect and block the line. Bear in mind, fuel isn't normally in that line unless the carb float sticks and overflows the carb. But in case that did happen, the line needs to drain itself.

If that doesn't work for whatever reason, I wouldn't use a check valve. I'd use a breather filter. UNI and K&N both make them. Here's the UNI....

http://ad-discountperformance.com/images/UP-102.jpg

They're just tiny little filters designed for breather lines. Mostly they're used for crankcase breathers but I see no reason you couldn't use one on a carb vent. I'd just be concerned a check valve might have a tiny amount of stiction and not allow the air pressures to equalize perfectly on both sides of the valve. A filter shouldn't do that. Actually, depending on the original line routing and possible alternate routing, I might just try leaving the routing as-is and just filter the outlet.


If you're sure it's this vent that is the problem, that's fine. But if at any point you become unsure, I'd check the float level first. I can't think through precisely why a clogged vent would only impact the carb on inclines. It might--I'm just not sure exactly why. However, a float level that is too high or too low could very easily cause stalling on inclines. The float level may or may not be adjustable. Many are--some require replacement of the float if it's off for some reason. There should be a spec for the float level in the service manual.

$0.02

[C-mo]

Thanks for the input. I will try the filter.

Perhaps the open line allowed trash to get in the carb, causing the float to stick. If so, draining the carb may have washed the trash out.

I appreciate your help.