Small Engines (Lawn Mowers, etc.): generic, k and n air filter, priority issues

Question
hi the problem i have is a small engine atv , it runs fine but when it gets warmed up it cranks but wont start and the starter slips. the pull cord start almost takes your arm off seems like high compression when hot. i think i narrowed it down to the intake valves because if i take the (new) k and n air filter off it starts up ? ever heard of this issue in your travels??????   thanks

Answer
Hi Steve,

It sounds like there are a number of issues going on at the same time.

The trick here is to narrow it down to what the top priority issues are.

It sounds like when warm there is a problem.   Possibly the carb.  

Possibly something is wrong with the piston or cylinder or both.  Did you try changing the air filter?

That is about all I can think of at this time.

Regards,
H.B.