Sounds like a whole lot of running around for such a simple problem!
Follow my list and I guarantee your 250 will be humming:
Start by pulling the #1 piston around to top dead center on the compression stroke. If you don't know what that means, I'll explain it to you, just ask.
Is the mark on your harmonic balancer @ TDC when the #1 piston is at the top of it's stroke? Make sure that that is correct. Now check to make sure that your timing is set between 10 and 12* BTDC.
ALWAYS make sure that your ignition is proper before you start messing with gas. Now, you said you're using points & condensor. I'd reccomend switching to a pertronix for now. It will really help. A DUI/DSII is a great upgrade, but get the parts you're working with NOW to start working right, and then upgrade from a good base. Otherwise you're going to end up just parts changing over and over.
NOW to the carburetor. Go buy a rebuild kit. Ever rebuilt one? They're fun and easy, especially the little one barrels. The nice thing about rebuild kits is that they will tell you the proper float level, it will come with a new needle valve (which is what I'm suspecting, to be honest with you), and a little ruler. The kit will also tell you the proper adjustment for EVERY part of your carb, so you will know for a fact that you're right where you need to be with everything. Change out all the rubber and gaskets. If you've never rebuilt one before, just take it slow, make sure you use a clean and well lit workspace, and keep all of the parts in a bowl or coffee can or something like that, and just be careful.
Just follow those instructions and if you don't understand any of it then ask me and I'll clear it up, but if you start from the beggining and quit jumping around like "well now THIS is happening what do I do?" it will be nice to you. Promise!
-Mike
