I have an 02 Eiger that has never had any problems until recently. It has 600 miles and doesn't get ridden much (obviously).
Background - my son rolled it a couple months ago and I'm just getting around to fixxing it. It started right back up when he rolled it and I thought it was just cosmetic. I've ridden it around the neighborhood a few times and all was well.

I had to replace the 2/4 wheel switch and then took it for a ride down the block and all seemed well but then it started chugging and wouldn't rev up. It idled fine but when you giver it gas it chugs and won't go, let off the gas and it idles fine.
Any obvious suggestions?

 

Have you taken the carb apart? On the side where the gas goes in to the carb there is a strainer there. After you take the hose off it will be stuck down in the port. Might be getting dirty.

Also perhaps the gas in the tank got stirred up. You can take the fuel valve off the gas tank and check both the strainers on it also. After you drain the gas. If both those filters and carb strainer is fine. I would just take the carb off and give it a good cleaning and see what you get.