Replace the main and pilot jets as I suggested. Make sure that the needle clip is in the stock setting (Typically 4th groove from the bottom).

Then set the air mixture screw to 2 turns out from lightly seated.

Check the choke cable for proper operation as well (I believe there is an adjuster in the choke cable itself).

I worked on a 1998 Trail Boss 250 (Wife's Grandfather) that had a very similar problem. It sat for a while, then wouldn't idle much and wouldn't accelerate without the choke and had almost no get up and go. I cleaned the carb very well and it was better, but still wouldn't run right. I took it apart again and sprayed carb cleaner through every hole that I could find. Again, still wouldn't run right. I had to keep thumbing the throttle to keep it running. I then replaced the Main and Pilot jets just for fun (About $10 for both of them) and that was it. I sprayed carb cleaner through the old ones countless times, and they looked perfectly clean, but once I replaced them, everything was back to normal.

 

Ok

I Pulled the Carb again pulled it appart cleaned everything with carb cleaner all ports etc. It has a 145 main Jet and the needle is set on 3 instead of 4 just a little leaner. Float looked good too. I also looked at the piston skirt it was fine as well as the piston had no scratches from what I could see through the port. Boot looked good also. So I put it back together and back in. Tried to start it and it backfired again killing my starter. I just left it there since I was ticked and went and worked on the 51 Chrysler sitting next to it.

A friend of mine gave me the service Manual on CD in PDF for it covers a few different models including this one from 96 to 98 so I will read through and see what I can find.

I hate carbs now I know why I bought a fuel injected Sled and fuel injected my car.

 

since it keeps backfiring i would double check the woodruff key on the flywheel and make sure it hasnt tried to shear. even the flywheel just starting to slip a little bit will be enough to make it run bad. while your at the flywheel check the crankshaft seals and bearings. if you can wiggle the flywheel and feel definate movement then the bearings are going bad and need to be replaced..that requires you to pull the motor and split it. replace the seals while your there too...

if the flywheel doesnt move i would suggest a leakdown test to check the seals to be sure one of them hasnt split.

 

Ok got back to the project.

Could I have a bad CDI or one of the switches be bad because now it will not even start. When I was looking at the plug cap I noticed it had a bad contact just fell off the wire. So I trimmed the end of the wire and screwed it back on. I have spark but could it not be sparking under compression or the throttle safety thing be bad or out of adjustment since I had the carb on and off a few times?

I should be able to start this thing without a battery correct? As the Battery is dead or is it needed to some extent?

I also noticed when hooking a strobe timing light up and spinning this thing over without a plug in that the light does not always flash if at all but I do seam to have spark another reason I am thinking it is an ignition thing.

The Key looks fine. I can't even get the flywheel off and if it is sheared it should pop off. Unless there is a trick to it but I pulled the nut off and put a flywheel puller on cranked it down. Tapped on it gave it just a little heat so as not to burn anything behind it still wouldn't go. So I just put it back together.

Todd