I just put together a running 250x out of 2 4wheeles. One was an 87 and the other was an 86 I got the 87 carb on there which is a 35mm carb. When running it is very very rich and gas leaks from the bottom, and if I just give it a little throttle it boggs down as does when I fisrt get on the gas when I am riding it. Anyone have any suggestions. 2nd question the carb that came of the 86 is a 38mm carb but it is missing the top triangular plate that bolts to the top of it. where can I get that piece and how much would I gain by putting the 38mm carb on over the 35mm. Thanks

 

Oh yea as for the mods I have I have a RCM exaust and a K&N filter with a 12 and 38 tooth sprockets. I don't know if that info will help

 

Hmm-- runnning quite rich, gas leaking from bottom and bogs just off ilde. OK- if you were to leave the fuel petcock open say for the night, would you have an empty tank in the morning? I betcha more than anything that it's the float valve. in the extreme case as this sounds, you may not even have a float valve in the carburetor. What the float valve is. is a small- needle point type looking thing that fits into like a sleeve that rises up and closes off the fuel to the bowl when the float rises, just like in a toilet tank. Typicly a dealer will want something rediculous like $25.00 for just this small item, but and entire carb rebuild kit can be found on ebay for around $17.00 plus shipping. Once the carb is rebuilt it can be fine tuned via air mix screw etc by reading the spark plug to check how it is burning....

 

Are you sure you have the right carbs? a 250x used a 32mm carb? 87 was the first year. Maybe your using 250r carbs.

 

Actually it only starts leaking when it is running. As far as them being the right carbs all I know is that that is what came on them. I measuresed the inside diameter and one is 35mm and the other is 38mm I know they are not off a 250r because the 250r uses a different style of carb from what I have seen. Is there ay place I can get parts for (Like that top plate I said was missing)? And how wouls I cross referance the carbs to make sure I am getting the right rebild kit?
These are the #s I could find on the carbs:

QB & QB
10AANA 01AAAJ

 

Im pretty sure my 87 250x carb is 35mm. I had fuel leaking out the bottom as well when i first put it on there. But it wasnt the float(though it could be your float) Or it could be the bowl. But my vote goes to the rubber seal on the plug that opens up to change the jetting. Its underneath there. I had to go get a new one to stop it from leaking. Honestly i wouldnt screw aournd with a stock carb just spend the dough get an edlebrock carb. Thats what im doing when i put in my built 250x engine.

 

I replaced my stock carb with a 35mm lectron and it was easy to tell the bore was much larger. I think the size is measured at the venturi .

 

.. That's a good point, getting a new carburetor altogether. Get one from a 300ex on ebay. It'll be around $40 plus shipping...

 

Ya those carbs a faily cheap from service honda. Doesnt even pay to mess with them. The 250x had trouble with the detent for the choke fluttering while driving it causing wierd power complaints.

 

So are yall saying I should go with a 300ex carb instead of rebuilding mine. Is there any power differance with using a 300 carb?