2003 kfx 400 its stock stock pipe jets and uni air fillter

its very clean wash it all time i seems to et hot quick and ffan comes on oil is new and full and anitfreez is good

 

Have you confirmed that the coolant is circulating?

My fan only comes on if I'm riding in the very slow woods, or if it is sitting idling. Is your can coming on while you are riding or just sitting?

I would first make sure the coolant is circulating through the system.

It can really only be a few things..... either your thermostat is not working or the temp sensor is not working.

 

it comes on when sit for around 5 min or when riding after awhile but am moving pretty good it shuts off pretty quick
the colant is moving oil is good and good colant level

 

there have been a few that have broken the fins off the water pump ,if your worried it may be worth a look

 

<div class="FTQUOTE"><begin quote>Originally posted by: honda400exracer3

it comes on when sit for around 5 min or when riding after awhile but am moving pretty good it shuts off pretty quick

the colant is moving oil is good and good colant level</end quote></div>

Well it should come on after 5 minutes of sitting still idling. Or even a few minutes of very slow riding.

If it shuts off when you are moving, that means the engine is cooling properly. Most sport quads will get hot if they are sitting still or going slow since most are designed to be moving forward. When you move you clear the hot air away from the engine and that makes more of a difference than the coolant alone can.