Unit has been sitting for approx. 5 years. having problems starting and over half throttle. have done the fresh gas, new filter and lines, checked fuel pump output and disassembled to clean. It just cranks when cold. Starts ok when warm. Also anything over approx. half throttle it bogs and puts black smoke out exhaust. Any idea's. Also it came from being close to sea level to around 4500 ft. Would this cause any problems????? Thanks for the help.