I turned my 5-HP Briggs push mower on it's side to change the blade. Now that dude smokes like a run-away locomotive. The smoke rolls out of the exhaust so thick that I can not see the grass. I mowed several minutes thinking the oil would burn off, but the plug fouled first. This morning when I went to try it again, the engine acted like it was locking up when I pulled the rope. I pulled the spark plug and the motor spun OK. Is there any fix besides tearing the engine down?