@MarkusG another hard start tip might be to follow your fuel hose from carb to carb and carb to firewall and then on to where it enters the frame. Make sure it always stays away from high heat sources like exhaust pipes and engine tins. This includes the fuel filter if it is back there, too. And if the fuel filter is an el cheapo plastic one, swap it out for a metal can version.
If the fuel line gets near a heat source the heat can boil the gas in the line and make bubbles that might force fuel to overflow the carb float bowls and make it super rich on start up when it’s hot. Those bubbles can also cause it to crank for a while to get gas past the bubbles and up to the carbs. @dlearl476’s suggestion of holding the throttle open on a hot start makes sense, too. Check on your fuel hoses and keep trying stuff on starts until you find what works for you.