SXF 250 won't start. Any suggestions?

[Evoroboto]

So its an 07 ktm sxf 250. It sat all winter but started up great in the spring and has run really well for 6 or so long rides. The other day it stalled when I started it up and it wont start since. I replaced the spark plug and it is sparking. There is lots of compression when I kickstart but it wont start. When I try to bump start it, the back tire locks up and skids when I put the bike in gear. Also when its in gear, the back tire wont spin even if I have the clutch pulled in. Clutch oil seems topped up and fine. I'm lost here hehe, any suggestions? Thanks!

[bajadog]

So the engine turns over, not seized, but it the transmission won't turn?

Take the chain off, and see if you can turn the counter shaft sprocket, if yes,
then see if your rear wheel bearings are frozen. That would be my first step.

[Evoroboto]

The rear wheel spins when the bike isnt in gear tho

[bajadog]

Okay,

Let's look at where you are now:

To have a four stroke run you need the following.

Air/fuel mixture

Combustion from spark

Compression

Valve timing

I think you should concentrate on the engine, and not worry about
the clutch now.

Not familiar with your bike, is there an e-start?

How old is the fuel?

Did you drain the carb before the winter?

[Evoroboto]

Its just a kick start. no e start. I didn't drain the carb before the winter. After the winter the bike started up after 10 minutes of trying which was pretty good. Its been starting up this year better than ever. Then it just stalled while warming up and wont start again. I've run 3 tanks of premium gas through it his season and its been alright. The gas in the tank was no more than a week old when it stalled out. I appreciate you taking the time to try to help me with this