My craftsmen lawn tractor has a 26 Hp Kohler engine. It starts and runs fine until I let out the clutch, then the engine immediately dies. The same thing happens when I pull the attachment clutch switch.

Sounds like a safety switch problem

It might have something to do with the timing key (you should have a repairman look at it).

"timing key ?" nah Mowerman has it, check you safety switches.

It happened to me! Went to a repairman, the timing key was shredded and now it can tow a lot (only 8hp! )

it happened to me! went to a repairman, the timing key was shredded and now it can tow a lot (only 8hp!!)
One thing I believe you missed here is the fact that he said it would start and run fine until he let out on the clutch pedal. IF your flywheel key is sheared, it would not be running fine, if at all. Most of the time when the flywheel key shears the engine will not start at all.

it might have something to do with the timing key (you should have a repairman look at it).
Oh, I thought it was an older mower

I didn't know it was a seat switch mower

I'm terrible at mowers