It's a 350X - get an O or X ring chain - the engine can take the added resistance. I like Sunstar and other brand name sprockets, not an EBAY no namer.... Expect to pay over 100$ for a good quality set.
I run 20" tires so I upped the front sprocket one tooth for more speed and it helped out some. 22" with a stock engine probably suit stock sprockets best.
I am running a 400EX carb, 450R exhaust, increased jetting and an open AB lid.....
I will either drop the rear 2 or 3 teeth or try to stuff a 15 in the front as it still has more to go. I think it will rub the case guard so I'll probably drop the rear.
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country