Engine problems again

I had just pre-flighted my airplane for this weekend's flight. I filled it up with gas and pushed the MX out of the hangar and started the engine. It started on the first pull. I quickly put in my ear plugs and muffs and gathered my GPS and such and shut the hangar doors. I strapped in and attached my GPS to the velcro strap that I used to secure it to my left leg. I pushed the throttle forward and the plane moved about ten feet and then the engine started to sputter. I tried to nurse the throttle to keep it running, but it didn't help. The engine quit anyway.

I got out and turned around and there was a huge cloud of gray smoke behind the airplane, slowly drifting away with the minimal breeze. I tried to start the engine again and it ran for just a few more seconds, billowing the area with smoke. I'm wondering what is going on here. I pulled on the rope again and again, but it still didn't start. I'm really miffed at this point. This engine only has about 15 hours on it and it never performed perfectly right from the start. I have informed the guy who sold it to me of all the problems I've had along the way, so he definitely knows the troubles I've had.

I suspect that maybe I've put oil in the gas twice without realizing it, so I drain all the gas. This takes about an hour because the fuel has to drain through a three-sixteenths diameter fuel line by gravity. Aggravating the draining process is the fact that I have to hold a can up to the hose while it's draining because it isn't long enough to put the can on the ground. Let's just say it is a very long, messy and smelly process that I'm not anxious to repeat. This particular visit to the hanger I previously filled up and mixed two five gallon cans this time, anticipating doing some serious flying, so I refilled the tank with the other can that I've mixed and try to re-start the engine. No-can-do. The engine is still showing the same symptoms, very wet rear cylinder spark plug and bunches of smoke when it fires. There's no way that I've overmixed two separate containers of gasoline....or is there?

I've had it with this engine and I'm going to send it back and request a replacement. As I disconnect the driveline, I slowly turn over the engine while the prop is not attached. As I do, I hear a click, click, click. The bearings on the crankshaft of a Rotax two-cycle are ball bearings, They have a certain number of balls, evenly spaced by a carrier. The clicking sound indicated that the carrier had somehow broken and the balls were free-floating between the inner and outer races. The bearing carrier (it's a phenolic resin material) broke and went through the engine. I'm not sure if this caused the problem, but it was certainly a condition that should not be present in an engine that had been "gone through" by a mechanic. This alone is enough to warrant a replacement. I continue the removal and take the engine home with me. I contact the guy who sold it to me and told him what had happened and asked for a replacement. I expect to get a hassle, but he told me he would take care of me. He would send a replacement short block and I could transfer components from the bad engine to the good. The engine I am returning is a Rotax 377 (368 cc). Because I had so much trouble with this engine that was supposed to be trouble-free, I ask the guy if he could send a larger engine, a Rotax 503 (500 cc) for no additional cost. He agreed and we said goodbye. I was to send the 377 back after installing the 503 and insuring that everything was OK. I'm feeling good about the whole situation now. I'm gettin' a 503! Cool!