I have been slowly working on a 2001 Trailblazer 250 that I have. Since it had old gas sitting in it, I went ahead and cleaned the carb. However, after putting it back together gas immediately starts leaking out the bottom of the bowl. I noticed when I cleaned it that the float arm was stiff, so along with a rebuild kit I also picked up a new float arm and pin. Took the carb back apart today, replaced all the parts that I could with the kit, put the new float arm and pin back in. Put it all back together, back on the ATV, turn on the gas..... and it starts leaking out the bottom again.

So, at this point I am stuck. I don't have any real experience working on carbs, but they seem pretty straight forward. I just have no idea why the gas keeps leaking out of this one. I am assuming I have done something wrong. Took some pictures of the carb itself and highlighted where it is leaking from. I am not sure if the vent lines are in the wrong place or what exactly. When I put the new needle in, it looks to be seated properly, but not sure if I should push it further in? I can see the float arm pushing the middle of the needle as it would raise while the carb is filling with gas.


Are the vent lines in the right locations? I saw a picture and moved the line that is to the left in the picture, to the bottom of the bowl where fuel leaks out of. Looks like another vent line comes from up near the handlebar area that connects to that location instead.


Leaks from here


Gas and what I assume are oil lines hook up here


Hope someone can see something obvious I am missing, or knows what the problem might be. It did not leak gas before I removed it to clean it the first time, so am assuming it is something I have done.

Thanks.

 

Sounds like a sticking float bowl was your original problem, but did you set the float bowl height when you replaced it?

 

I did not set the height, trying to figure out where I should set it at the moment but not getting much luck with what the height should be.

 

Take your float needle out and look into where the little rubber seal seals up. If there is anything gummed in there it will prevent it from sealing. To clean this, take a small wooden dowel rod and sharpen it with a pencil sharpener, poke it into there and twist it on the mating surface, should clean it up. Also check what your manual says float level should be and set accordingly.

 

It looked pretty clean where the needle seats, I had sprayed a bunch of carb cleaner all through there as well to be certain. Will definitely give it a second look though just to be sure. I don't have a manual, so am trying to research what the float height should be, not sure if that is the problem though as it leaked fuel with the old float (although that could have been sticking) as well as the new float arm. But, also worth a look at least.

Is it possible the vents could cause it to leak? By mistake I had what would be the bowl vent hooked up to the vent that goes up to the handlebar area, although I doubt it would cause it to leak like that, just trying to rule that possibility out. It looks like the vent hose that goes up to the handlebars is missing, I may be able to easily replace it with some airline tubing I have laying around though.

 

I dont think your vents will cause it to leak. Additionally, all the vent hoses coming from the carb should terminate below the level of the bottom of the bowl to prevent water inhalation. If you have to guess at float height usually parallel to the plane of the face of the bowl gasket is a good guess. Next time it does start leaking too give the bowl a good few hard taps to try to get the seal to set, I have to do that from time to time on one of my older dirtbikes. Ultimately though it should still run regardless of the fuel dumping overboard, its dumping to prevent it from going into the cylinder, your fuel feed system should still work. Sounds like you have issues other than dumping fuel overboard. Take the carb completely apart and use some compressed air to blow out the passages. Does your engine have adjustable valves?

EDIT: Would probably be smart to pull up a parts breakdown of your carb to ensure you arent missing any components.

 

Funnily enough this all started because it would not run at all, it ran a while back but had been sitting and no longer ran at all. After looking into it some it turned out the fuel petcock was completely gummed up preventing any fuel from getting to the carb. After replacing the petcock I then took apart the carb to clean it, when I put it back together again it started leaking. But, while having it torn apart I noticed the float arm and pin were pretty crappy looking, so decided to buy the rebuild kit as well as the new float arm and pin. Going to try and search the manual and correct level for the carb, but in the meantime I had the old float arm still on my workbench, so just took the new one and placed them side by side. The old one had about a 2mm bend to it which I have replicated on the new one. From the kit I replaced the gasket, main jet, needle and piece the needle seats into (not sure on the correct name) in addition to a new float arm and pin, I also sprayed carb cleaner through all the passages.

Hopefully the weather gets above freezing later and I can put the carb back on to see how things are. Will be nice to get this thing running.

 

Ok a couple things here. Did you confirm before replacing all your jets and needle that the new jets were the same exact number jets? and what position did you set your new needle E-clip at? Most of the time "rebuild" kits come with some random assortment of jets usually not what you had in there in the first place, if you just slap in the new jets, chances are it isn't going to run right. Get your old jets cleaned and back in there and see if it runs better. Is it a OEM carb or a chinese knockoff carb?

 

My apologies, I did not replace the needle that uses the E-clip, just the needle that the float pushes up to close the fuel. The kit only came with one jet and should be correct for the carb, it did come with a new needle and e-clip, but I left the old ones alone. As far as I am aware it is an OEM carb, it's a Mikuni, but I could not tell you if it is an original or knockoff.

 

If it says Mikuni on it chances are its at least OEM if not original. That is good news. The jet you replaced should have had a number stamped on it. That number should have been the same as the one it replaced, if it was, youre good. Is the float needle a metal or rubber tipped one? I've had issues with metal ones seeping/dripping a little fuel when the engine is off, not usually much though.