Ok guys,
I did some trail riding on my raptor a while back. It ran fine. Got home and the bike wouldn't start. I thought, "ok, need a new battery". Got a new battery. Put it on. Bike still wouldn't start. Turned over, but wouldn't start. Cleaned the carb. Adjusted the floats. Adjusted the valves. Changed the gas. Put in new spark plug. Using some starting fluid got the bike to start and idle with the choke on. Valve sound was more noticeable than it was previously, but I didn't think it was too terrible since I was within specs on my adjustments. Turned off the choke and the bike wouldn't idle on it's own. Went back out today to try again. Starter now only engages intermittantly. Tried a different battery. Same problem. Sometimes takes 2-3 seconds before starter will roll motor over. I think when it does I hear a "slapping" sound. It's pretty loud. Started twice for about 2 seconds and died. Fuses are good.

 

Start with the basics. . . fuel, air, compression and spark. . .

My guess is carb. The battery is probably just weak from all the attempted starts.

Pull the carbs off and give them a severe cleaning.
Loosen the gas cap - to make sure venting isn't an issue.

Loose valves will decrease performance but, tight valves will make it difficult for it to start when cold.

 

Mods?
Have you rejetted?

 

Bike is completely stock. No mods at all. Oh, and when i had the carb apart i checked the needle valves and they seemed ok to me. Forgot to mention that before.

 

Did you check the floats. . . were they sticking at all. . . freely moving? Turn the fuel on and play with the floats a little to see if everything is working as it should.

Check the pilot jet to be sure it isn't clogged or anything.