04 warrior motor carboned up?

[riverrat]

A friend of mine has a 04 Warrior and he took it his dealer due to poor running quality. The dealer told him motor was carboned up bad? Any ideas?

 

[Thumper1000]

Run some Seafoam through it, it should help and won't hurt for a couple bucks.

 

[RX1Jim]

How did the dealer determine there was an excessive buildup of carbon? Did they do a compression test or a leakdown test?