Need advice on engine rebuild
My son recently bought his first sled--a used 2008 Polaris Dragon. After a few uses, it freezes up--it is a Dragon. Dealer says it needs cylinder, et al. Says he will repair it to "the latest and greatest". After $2000 of rebuild he says it's "good to go" and my son is off for a vacation ride. I used to race motorcycles and know the 2-stroke ritual and advised him to follow the book on break-in (even though the dealer said he already broke it in). He carefully spent 5 hours following the book. On first day of real riding engine light comes on, he stops, cools it off, light goes away. Light comes on again later, he stops, light then goes away for 1-1/2 days of riding. He thought light came on because it had a rich mixture from oil manually poured into gas tank by dealer. On next day engine bogs badly (no light ever appears). Vacation is over for him. Takes sled back to dealer. Dealer says it needs total new engine. Says the fuel filter was clogged. Son asks why they didn't check it/change it on engine rebuild, they say he didn't ask for a service. (He asked them to fix his sled, didn't tell them what to do or how to do it). Dealer says he must have bought bad gas even though 30 other riders in his riding group had no issues with gas.
Dealer refuses to rebuild, repair or refund.
My question: is this bad gas thing for real or just a dealer excuse? What should he have done differently? Does he have any recourse? I think the bad fuel filter may have caused the original engine breakdown and was never found/fixed by the dealer. Note: 300 miles from rebuild to breakdown.
Your expertise and thoughts are welcome.