I have a 89 trail boss 250 4x4. It ran perfectly when I purchased it. The next day it will not start and run without being toggled between full choke. I have good spark and compression. I installed new needle and seat. I cleand every jet. What have I overlooked?? Why would it just shut down like that over a trailer ride away?
any suggestions would help.

 

You have removed the carb and cleaned it entirely?
Seems to me you are running too lean on the pilot circuit. Not enough fuel. When you pull the choke on you get a very rich fuel mixture and then it runs. Could there possibly be an air intake leak between the carb and the intake mainfold? Be very carefull here you could sieze the engine if there is an air leak. This is a 2 stroke correct?
Did you have the float bowl off the bottom of the carb?

More info here and we can solve this.

Keith

 

yes it is a 2-stroke. yes I have removed the carb completely and taken every jet out and cleaned them including bowl. I even put gas in float bowl to see if they floated. I did not look for a leak between the carb and jug? posssible?

 

Yes it is very possible to have an air leak between the carb and the jug. If this is the case the air fule mixture will be too lean and eventually lead to a seizure. I cannot really see this causing the engine not to run at idle though unless it is a very large air leak. An easy way to test this is to try and spray a combustable fuel around the intake after the carb and listen to see if the engine RPM's increase any. I assume
propane from an unlit torch would work good as long as you are carefull.

If you could somehow pressurize gasoline (maybe with a empty hair spray bottle) you could spray this at the intake after the carb as well. See if the RPM's increase.

Did you replace the float bowl with a new gasket? Or did you use silicone on the fuel bowl? The reason I ask is gasoline will break down the silicone seal and allow little ***** of silicone to get sucked up into the main jet, plugging it.

If you get the engine running with the choke on,then shutt off the choke and snap the throttle, are you able to keep the engine running?

Keith