Neighbor just picked up a atv and we finally got it going. The exhaust pipe was cherry red after about 1 minute of running. He took the carb off and cleaned it, but im not sure how well he did that. What would be the most likely reason for it to put out that much heat. Lean fuel mixture?

Yep. Running lean can do it.

I couldn't do with out this tool on cleaning varnish from small jets and orifices. You just have to be careful and not enlarge/gouge out the jets when cleaning carbs. http://images.motorcycle-superstore....ire_Set_--.jpg

So, you think its a lean condition, and not a timing or valve issue?

Stator timing is preset,ignition timing and advance is through the cdi. If the exhaust is cheery red most times it's because of lean or partially stopped up jets or possible air leak from a cracked/split intake manifold under the clamp holding the carb. This was a problem on the 700s.