I could not get my 96 trailblazer to start with the pull start or the starter without using ether. I cleaned my carb that didn't help, I sent it to the dealer and had it soaked and set. It still would not start without ether. I than changed all the hoses on the carb and replaced the fuel line and filter. Still nothing, I got a new battery, plug and the magnetic switch, all fluids and I removed the air box. Still needed ether to start, the plug is a little black so it is getting fuel. It would start every now and then with the starter after a lot of cranking but maybee 1 out of every 30 times. I thought it must be compression I did a check and it was 92 psi so I had the head shaved .020 and bored .020 and I bought a weisco piston, I just got it back and am going to do the rebuild this weekend. My question to everyone is I have never jetted or adjusted needles in the carb I am affraid it still wont start after I do the rebuild and I dont want to crank and crank the piston with no lubricant. Could my problem be jetting maybee, and with the new motor work should I change the jet size or needle position before I do the cylinder. All settings are exactly as I got the machine new in 96 on the carb.

 

Once it did start it would idle for a little bit and then die after about a minute, and for some reason adjusting the screw to the thumb throtle had way to much response just a little turn and the engine would race or die this worked alot better than my idle screw. This made me think maybee something may be wrong with may cable or cable adjustment.

 

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A cracked reed can (sometimes, anyway) be the culprit of what you are describing. It would explain difficulty starting, and the rev/die nature of the engine. I am assuming, of course you didn't fiddle with the carb before this started acting up.
It could be a plugged port in the carb also.

To help prevent siezure of a rebuilt engine, run pre-mix thru it until you get the carb set. This will at least give you a little bigger margin for error.

 

No reeds on a trailblazer.

 

DUH, you're right. Sorry about that. I am so used to tinkering with the 400 engines, I forgot the 250s are cylinder ported.
After re-reading your post, it has to be lack of fuel somehow, likely in the idle circuit. That would explain the need for ether, plus the rev fast or die nature of the engine.
Maybe the pilot jet is plugged? That is the little bugger that is next to the main jet if you view the carb from the bottom with the bowl off. Again, I am looking at the diagram for a 400, but I assume they are about the same.

 

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