Fired up Bomberboys bike today after he had some problems with it a couple weeks ago. Last weekend checked comp. and did a leak down they were OK. Spins over freely by allen wrench in the crank, fired right up todaywith a lot of growling in the bottom end. Looked in the oil resevoir, no oil returning, pulled the sending unit, no oil pumping out there either. How bad do you think its damaged the crank and rod? Can just the bearings be replaced or will it need a new crank assembly? What kind of cost? Thanks, John.