What TimeOutRV shared about seat height is a really critical element. I'm just north of 6' 2", and the stock seat post is fully extended. If I were any taller, I would need to swap out posts. But this one works, and I 'mount' the bike some so than merely sitting down on the seat. Watch how much bend you have in your knees. At the bottom of the peddle cycle, your knee should pointed down, at nearly a 45 degree angle to the ground. If your knees are coming up higher . . . say almost to the upper bar . . . they you're putting too much strain on your hips and butt, and your upper body isn't sharing the load. This will quickly sap a rider, and almost guarantee sore spots.
Happy riding, and with time, your muscle memory will lessen the discomfort.
2016 Coachman Leprechaun, 319DS, Motorhome, Dodge Durango Toad