gas pouring out of air filter box

[derekmelton]

Hello, my son and I just bought a very clean 2008 250 nighthawk. It's not cranking, turns over just fine and was running recently but now when we turn the gas to 'on' and try to crank it, gas leaks out of the air box. Would this be a stuck float in the carb?

[Larry Fine]

Welcome to the forum.

Yes, it sounds like the float valves leak. Does the 250 have a vacuum valve?

Gas in the oil destroys its lubrication abilities, so don't run the engine until you're sure the oil hasn't been contaminated, or until you change it.

[mollusc]

"Cranking" and "turning over" are synonyms.  Do you mean that it's not firing?

[derekmelton]

"Cranking" and "turning over" are synonyms.  Do you mean that it's not firing?

Right, not firing. Turns over/cranks good but won't fully start. Gas is dribbling out of the air filter within seconds of opening the petcock to the ON position

[mollusc]

Definitely sounds like a stuck float valve.  Sometimes knocking on the side of the bowl with the handle of a screwdriver will dislodge them.  Worth trying before wrangling the carb out of its nesting site (although I think the CB250 is not so difficult to get to as the 4 cylinder Nighthawks).

[derekmelton]

It's definitely not. I'm just a bit nervous about making the situation worse.

[mollusc]

Since it's not operational as it is, you can't really make it worse.  As I mentioned on your Facebook post, I would try removing the float bowl in situ just to see if you can inspect/clean the float valve.
And yes, it is important to use a proper JIS bit.  Those are NOT Philips machine screws, and you will strip the heads if you use the wrong tool.

[Pete in PA]

Some of the same people are here also.

Same answer:  Get a manual, watch some YouTube videos on it and do it yourself.  Been about 7 yrs since I had a 250 Nighthawk. only 1 carb.  Comes out super easy, simple one to work on.
Get the GREAT satisfaction of DIY!

Also Carbjetkits.com
A little richer REALLY wakes this bike up.

When checking valve clearances set to min.  More lift and duration. More power.
It's really a great bike, will do 80 mph eventually with the jetting.
Good for back roads where cars aren't trying to run you over at 70 mph.

[Northern Rider]

Also if you have that much gas pouring out, be sure to check the oil level in the crankcase. Gas may have also flooded into the lower end. Like mentioned earlier don't start the engine until you know what went wrong or where the gas ended up. You may have to drain the old oil and gas mixture and refill it a couple of times to make sure all the gas is out of the lower end. Better safe than very sorry! Good luck!