I recieved an old yamaha enduro 175 from my grandparents as a gift a while back, but since it had been sitting so long, it doesn't work the best. Every time I try to hit the gas, instead of the r's getting higher, the motor starts bogging down and if I don't let up immediately, the bike dies. A friend said it was the carbeurator (sp?) if so, what should I do to make it run better?