I purchased a 250x that had been sitting for some time. I couldnt get the thing started. Replaced the plug with a new one. Napa did not have the same NGK plug that was in it. They looked it up and found a champion plug that it called for. He did tell me that it was a little hotter of a plug. I put the plug in and it fired right up with the choke on. I tried to take it off choke to run and it would die. I then took the carb off, cleaned every possible thing in it. Put it back on and the first time I was able to take it of choke but it would pop and crack and the exhaust is getting extremly hot within a few minutes. Took carb off again to see if I missed something. Cleaned it once again. This time it would run a bit better but wouldnt idle without constant gas. The exhaust is getting way to hot. Can someone tell me what is going on?

 

You need to completely remove the pilot jet from the carb body. Its the one with the slot, for a screwdriver. Theres no way to clear it, unless its removed. If you cant see light come thru the center hole, of the pilot jet, once its removed...its plugged. You can try soaking it overnight in carb cleaner, but if it doesn clear out, go get a new one..they are about 5 bucks at the dealer.
The popping and hot exhaust are from running lean.

 

Guess I should have mentioned it had been re-jetted for the aftermarket pipe. I did remove the jet, blew it out and soaked it. I can see light through it. Each time I clean it seems to run better but still not right.

 

What else is not stock? Are you running an air box lid? Did they jet for that? What were the jet sizes they put in?
Id guess the pilot jet is either too small, or the mixture screw is too lean.

 

It has an airbox with a k & N filter. I know that it ran with the current jet in it. He told me that he jetted it to match the fmf pipe, but it had been sitting for sometime.

 

Have you drained out the old gas? And replace it with new?

 

Hondabuster first off. thank you for being so attentive to the posting. nice to have quick responses to an irritating issue.

No, I personaly did not drain the gas. the previous owner told me he put new gas in it. he also told me he pulled the carb and checked it but you could obviously see that he hadn't.

 

Not a problem, too cold outside today, so im inside drinking coffee, and planning the summer trip.
Id try some fresh gas, and then look real careful at the connection between the carb and the head. Look for being loose, or the rubber being ripped. If you have an air leak there, itll really run lean, which is the situation now. And as long as youre under there looking..check the other end of the carb, and how it seals to the air snorkle.
Then count the number of turns, the mixture screw needs to be turned in, to hit bottom. This is so you can have a reference as to where it started at. It should be about 2 to 2.5 turns out. Going out is richer.

 

OK came home from work and tried a few things. I put fresh gas in it. blew out tank. I attempted to adjust the air/fuel mixture screw which was 7 turns out. I tried it at several points. heres what it is doing now.

I start it with choke on. let it warm up a bit. Then I flip it to run. now when i flip it to run it revs really high then drops off to where it idles but almost dies. sometimes does. it just doesnt appear to be running smooth at all and will pop when giving it gas.

 

I also went out later and pulled the petcock not realizing that it had a screen in it. It had a bunch of crud built up in it. CLeaned that out and checked flow. Not sure how fast or how much fuel should be coming out. I would imagine a steady flow. Still didnt seem like a lot so I re-installed the tank. It fired up and began to run better then before. Only problem is now it wont stay running. I looked at the line running from the petcock to the carb. appears to be getting pinched on the two bends to the carb. Gonna pick up another line and try that. Ran smoother then before.