Small Engines (Lawn Mowers, etc.): sr1533 snapper rideing mower, head gasket, leak down test

Question
snapper rideng mower with 15hp kohler engine.wont start has new spark plug just cleand carb.has spark at plug put small amount of gas in intake still wont fire the first time,model cv15st.disp[cc]426

Answer
Have you performed a leak down test to check the valves, piston and head gasket?  Could be a compression problem.

Is the flywheel key partially sheared?  This is rare in a rider, but I always check.
How old is the mower?  When was the last major tune-up?

Let me know.
Eric