My friend has a trx 90 for his son. It has been sitting up for about seven months. Since he has very little mechanincal knowledge, I decided to help him get it running. I replaced the battery and cleaned the carb. The bike runs great with the choke on, but as soon as I turn the choke off the bike dies. So I ran the bike with some fresh fuel to hopefully clear it out. I did not see anything in the carb when I cleaned it and the bike looks brand new. I searched the forums prior to posting but did not have much luck. I am not a four wheeler mechanic, but I am mechanical inclined.

Thanks for any help and a great forum.

 

First, these are very cold blooded, so you usually need full choke for a very long time to get it warmed up. I assume you have gotten past that point, and you are saying that even when well warmed up it will not run without choke (????).

If that is true, then it sounds like an air leak somewhere, and the choke is cutting down the amount of air and getting the right mixture back. Look for a bad air filter element (oiled properly???), improperly installed air filter, or a tear/crack in the rubber boot between the airbox and carb.

 

I did not see any cracks in the tube from the box to carb. and the filter looks brand new. Can I clean the filter with K&N cleaner kit? The air filter box also looks to be in great shape.

 

Just clean the filter with dish soap and warm water.

If the air intake system is ok, then you probably have a clogged jet. The jet isn't delivering enough juel, so cutting down the air flow gets you back to the correct mixture.......