My '78 DT250 wasn't flow any gas through the carb, so I took the bottom bowl off, cleaned out the gunk with carb fluid cleaner, dried and reassembled it. However the needle valve keeps slipping out when I slid the bowl back in.

So I turned the carb sideways so that the needle doesn't fall out, and set all four bowl bolts in place. But as soon as I turn the fuel petcock on, within 6 seconds, I have gas streaming out of the vent near to the throttle screw along with pipe air vent at the bottom.

What did I screw up? The needle valve sits in the recessed opening, just above arm float. And when the bowl fills up, it is supposed to push up the needle so that the fuel doesn't stream in, right?

I can post a video in the next couple of days. Maybe it would be easier to describe.

Any help would be appreciated.

Have you checked the float height? Floats/needle the right way around?

Have you checked the float height? Floats/needle the right way around?

I believe so. The floats just move up and down on the brass rods. As for the needle, there only seems to be one way to have it stay seated...round stock end recessed w/ the needle point resting on the seat lever, that rests on top of the two levers protruding from the floats, right?

But I'll take another look at this evening.

I believe so. The floats just move up and down on the brass rods. As for the needle, there only seems to be one way to have it stay seated...round stock end recessed w/ the needle point resting on the seat lever, that rests on top of the two levers protruding from the floats, right?

But I'll take another look at this evening.

Post a picture of the inside of the carb if you can get around to it.

have you put the floats in upside down? I suspect the little pegs that operate the float arm are not moulded exactly central to the float diameter.

Okay, i figured it out...I had the float needle upside down. Just had to reverse it.

Thanks for the help.