[2>>4]

Last week I noticed some gas leaking out of what appears to be the drain port on the bottom of the carb on my 04 KLR 250, arrowed in red:

I looked up the parts diagram - supposedly the screw that seals the drain (arrowed in green) is supposed to have an o-ring on the end, but it didn't. I'm wondering if it's as simple as adding the o-ring to seal off the port?

Seems like it should be, but the reason I ask is because the end of that screw is tapered in a unique way and I couldn't figure out where an o-ring would seat on that screw that would allow it to seal the cavity when fully tightened, and then gradually allow fluid to drain progressively as it is loosened. Here is a picture of the screw:

Is the o-ring supposed to reside on the tapered end, within the carb?

Also, here is a picture of the internal of the bottom case of the carb:

What is the purpose of that uniquely shaped hole in the bottom, as well as that brass rod? I think the rod is for some sort of overflow bypass. What concerns me is that I looked at the configuration and it appears that the overflow port would bypass the drainage screw, regardless of its position.

So I'm wondering if the leakage is just caused by the missing o-ring, or if the settings on my carb are incorrect allowing too much gas into the bowl causing it to spill out the overflow.

Any advice is appreciated.

 

[2>>4]

When I took the carb apart to clean it, I guess it's possible that an already-degrading o-ring could have been further obliterated by the carb cleaner, but I'd say unlikely.
Referring to the inlet valve, are you talking about the port that is sealed by the needle on the float bowl? The needle itself looked fine; I'm wondering if somehow the float isn't pressing up on it hard enough to get it to seat.

 

[Tom Schmitz]

Inlet valve issues are seldom the fault of the float. Almost all used inlet valve needles look good, but they aren't if there is a leak. The seat can also be a problem. If you want to fix it, then clean the seat and replace the valve, then check the fuel level in the bowl.

Fill the carburetor with fuel and attach a hose as shown. Open the drain screw and observe the fuel level in the hose.

 

[eamartin]

Principles are the same, but just to be clear, the carb in question is from a KLR 250, right?

 

[pdwestman]

Is the o-ring supposed to reside on the tapered end, within the carb?

NO!
The OLDER model KLR's & KLF atv's used a courser threaded cross-top screw (fit flat or phillips screw driver), not 3mm allen bit. Those screws had an o-ring between the head of the screw & the threads. Its purpose was to seal drippage from the threads of the screw & the bore of the hole when using the tubing to confirm fuel Level like Tom's pic of yellow hose..

I don't know where that bowl came from, but it ain't supposed to be on your bike. The brass pipe is an overflow pipe. In the event that your fuel inlet valve should fail, that overflow will allow gas to dribble out the bottom of the carburetor instead of filling up the cylinder and causing hydro-lock. It is a wonderful idea, but the EPA made them illegal a very long time ago because, gasp, think of the children and the whales. They aren't found on modern motorcycles in the US. Certainly not on a 2004.

The float bowl in question may be from the Newer off-highway KLF / KVF atv's, which are still allowed to have the overflow stand pipes. Go figure! Bouncing around in the rock piles, the overflow pipe is more likely to occasionally drip on gods green earth.

I would suggest either using emery cloth on the taper of the screw or replace it. And possibly use a Q-Tip & metal polish on the taper Inside the bowl, there could be 'grit' embedded into the taper. Those screws only need to 'barely snug' but people tighten the crap out of them, trying to stop a drip that can be coming from An Overflow Pipe & too high of fuel level or caused by float needle & dirt brass seat!

Then with the bowl still removed, fill it 3/4 full of gas and confirm that the taper is Not Leaking.

 

[2>>4]

Thank you guys very much for the info.

Any recommendations on the best place to order these parts? Last I checked bike bandit said 1-2 weeks shipping time; I'd like to get it sooner than that if possible.

 

[2>>4]

So I took the bottom off and filled it with gas - no leaking from the drain screw, and the o-ring that's supposed to be there. I put the carb back together and did the "tubing test" with the drain open and the line running up the carb body to see how high the gas was going and indeed it was probably a quarter inch above the interface between the carb body and the bottom bowl. I took it apart again and inspected the valve and it looked flawless. The valve seat had a tiny burr on it that I was unable to remove, but I proceeded to polished the valve seat with a q-tip and some carb cleaner and put it all back together and the level in the tubing was lower, and no leaks. So it must've been some sort of minor build up on the valve seat that caused gas to slip by and get to the to the vent tube.

I'm quite surprised that polishing it solved the issue. Upon initial inspection I couldn't see anything obvious that would have prevented it from making a good seal. I know there isn't much force from the float pressing the valve into the seat but I would think if the seal were that susceptible to leakage due to a minor buildup (which is of course inevitable in a carb) then they would have come up with a different design.