Hello I ought a old yamaha xs400 a few days ago and when I bought it the bike rode fine. The problem now is that I think I flooded the engine by not turning off the pet cock properly. I checked the oil and when I drained it was brown muddy and smelled of gas. Before I completly drained the oil I tried to kickstart it and the bikes starter seemed more stiff then usual. Even with my full weight (250 lbs) it would go half way down then on the second it would go down but with a-lot of back pressure. I know I will probably have to change/clean the plugs and get new oil but I.m worried of internal piston damage. The engine turns over just with more force then it should.