how much mileage can i go before i have to do a valve job...and what are the consequences of not doing a valve job. bought rc51 used with 5000+ miles on it...now has 17000 miles...lost the fwd cylinder...50psi...and the rear cylinder is at 110 psi.. one shop guy says that i have bent valves...air coming out of intake and exhaust. any info be much appreciated...v twin (especially rc51) for life.