I recently purchased a 1984 TRX 200. They said they rebuilt the carburator, but they didn't change the spark plug. When I first got it, it would start and run, but it wouldn't idle no matter how I adjusted the idle screw. It had an old champion spark plug in it. I replaced it with a factory NGK and replaced the air filter.
I took it out, it started fine but it still wouldn't idle. However, when I would try to accelerate it began to cut out quite a bit until I got it past a certain point on the throttle. I parked it for about a week, but now when I try to start it, it won't start. I even put the old spark plug back in, but that didn't help.

I did take the spark plug out (both of them), and ground it against the engine. When I hit the starter, there were some small blue sparks. I don't know how much spark there is supposed to be so I don't know whether it is an electrical or fuel problem.

Any suggestions would be appreciated.

 

Try replacing the jet and the needle

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