I'm very new to ATVs. I just got a 1999 TRX300 2 wheel drive. I notice on the side of the engine there is this screw there that is just bugging the heck out of me to know what it does. It has the words Increase and Decrease above it. Could someone please tell me what this is and what it does? Thank you

 

That is your clutch adjustment.

per owners manual:

1.Make sure the ignition switch is off.

2.Loosen the nut and turn the clutch adjuster counterclockwise until you feel slight resistance.

3. Then turn the adjuster 1/4 turn clockwise and tighten the lock nut to hold the adjuster in this position.

4. After adjustment, start the engine and test ride the fourtrax to be sure the clutch is operating properly.

 

Sorry for such a dumb question but how do I tell if its not adjusted properly?

 

I have had my 98 TRX300 since new have yet to adjust it or felt it was needed. If you get on the machine and you are giving it gas and the rpm's are rising and you are not going anywhere I would try the adjustment.