If the engine is hard to start when hot, it can sometimes be because the carburetor is flooded. One technique here is to slowly put your foot on the accelerator (so that it doesn't flood with fuel) and then crank it. If that doesn't work, make sure all the connections are in good health - battery, HT leads, etc. Also check that the choke is upright. If none of this work, check that the air filter isn't clogged, the starter solenoid isn't failing (try replacing with a known gd one), the battery is in good health, and the battery ground connection isn't corroded. One issue could be that the system is suffering from vapour lock - where the heat from the engine causes the fuel in the surrounding lines to vapourize before it can reach the carburettor.