Need help with no start on Honda 450 engine

Hi guys, please bear with me on this one. I know this is the vital site but I'm having no luck on the 4-wheeler forums. My brother has an '07 Fourtrax 450 ER that won't start. I was hoping there would be enough similarity between this engine and the CRF450 engine (pre-EFI) that someone might be able to help.

So, the quad hasn't run in 3 years, but it ran fine when it was parked. The fuel was drained out of the carb. The carb has been cleaned out with a blow gun, and pressing the throttle shows gas shooting up from the accelerator pump. There is spark and compression is 50 PSI (this is within spec because of auto-decompression). This is an electric-start engine, no kickstarter.

Any ideas? We did try gas in the spark plug hole but it just back-fired. I've read on the quad forums that the timing may be off but it ran when it was parked, no changes. I'm just an old 2-stroke guy so I'm at a loss with a somewhat modern 4-stroke engine with a FCR carb. Thanks!