I just bought a 99 TRX 300 that has been sitting 2-3 years that I'm trying to get running. I drained the tank, checked the screen (which was clean), put in a new sparkplug and battery. BTW, the old spark plug was oily. At first it just turned over without firing so I pushed the primer button on the carb and it would fire for a few seconds. Then from reading the Clymers service manual, I pulled the choke cable and sprayed some WD40 on the o-ring to make sure it wasn't stuck. After that, it ran longer at idle, but when you tried to give it gas, it would either die or backfire. Any input would be appreciated.
On a side note, I've gotten some good info off this site since I bought it a few weeks ago.
On a side note, I've gotten some good info off this site since I bought it a few weeks ago.