its a high revving 250 4 stroke. the cams chains and valves make all the noise i rode mine with a mx helmet and thought it was going to blow but its is normal as long as you broke it in right, but some people ride the piss outa there's bran new and just do their own brake in procedure. street helmet its pretty quiet except when you buy a power core 4 then you wont really hear too much engine noise. mostly muffler