Please help!

I have a Craftsman Lawn Tractor 17HP Kohler Engine and I bought it in 2003 so its fairly new.

When I start it up with the choke and then let it idle it seems to run OK, I can even drive it around a bit.

However when I engage the mower blades to cut the grass the rpm seem to drop to the point the engine is going to conk out and the mower is backfiring.
I have read the owners manual and it seams that when you engage the blades it is also attached to a clutch spring.. I am not sure if that has anything to do with it but darn why the heck when the blades are engaged does the motor conk out?:mad:

Any advice would be so greatly appreciated!

Thanks in advance, and let me know if you need anything clarified.

Thanks!

Check your sit switch