I am a begginer rider and i do all track riding. I will be racing about once a month. Are these bikes reliable. Do you have to change/ adjust the valves alot. After how many hours should I change the top end. I wont be riding it to hard since I am still a begginer but I wont treat it like a baby. Is there anything wrong with these bikes. I am 14 and before this I was on a 2 stroke. Thanks