my original duel exhaust was at that time to be replace with after market exhaust. I found it cheaper to go to a single exhaust from a duel exhaust...was wondering do i lose horsepower and performance in doing this. what is the actual horse power rating for this bike..1981 yamaha maxim xj650..also is there anyway possible to find another fuel tank that would hold at least 5 gallons of gas rather than the normal 2 1/2 gallon tank that is all ready on it..( 13 liters )