Start with the spark plug. It is arguably the easiest thing to check. They often get fouled. You can clean it off, but I have always simply paid the few bucks, gapped it, and thrown a new one on the bike. Next up would be the CDI, which on my enduro is under the seat. It is a module that can be changed easily, too (like how easy the spark plug is). Once you determine that it is not either of those two, then it could be a carb issue. My suggestion is to take it to the dealer and use your warranty. Make sure you ask about the spark plug (if it is fouled, it will be very black) and the CDI so they at least think you know what you are talking about in order that they don't try to take advantage of you. You can't really check the CDI yourself unless you buy a spare one (they are not expensive) to see if that is the issue (or if a friend has a similar bike to exchange the CDI for a while), so that one is harder to diagnose without a spare one nearby, but the spark plug is very straight forward provided you have the spark plug tool. Just be careful taking the plug lead off so you don't pull the wire apart.