welcome to the site, and you need to clarify things better
its a 300, about 20 hp IF that when they were NEW! which they ain;t been ina LONG time!
so don't expect it to be no monster ATV, just cause you seen one on YOUTUBE do something your's doesn't
odds are the one you seen wasn't STOCK, and most likely worked up some
what do you mean NO power
or low on power as to in GOOD condition one would be
have you done a compression test?
how many hr's or miles on it, is it stock, did you add BIG heavy tires to it??
has it been used as a boat and sunk??
all this stuff maters and answers will get you better help
These trx300 are not fast either; their advantage is light, low and nimble. They are the best for riding narrow trails--good for new riders because the ease of operability inspires confidence. Sounds like you got a good rig might just need some maintainment ?