I'm confused. I was under the impression that main bearings were lubricated by the crankcase oil and not the two stroke oil from the fuel mixture. I was thinking the two stroke oil was used for lubricating the piston movement and is burnt off (or mostly) during the firing in the combustion chamber. Am I right? I was told otherwise but I'm still not convinced.

The reason I ask is because I just looked at my sister-in-laws Blaster. She was complaining that it wasn't running correctly. I started it and it sounded great for about 30 seconds. It then started rattling. I figured it was piston slap (top end has never been replaced) and I went to work to take apart the top end.

After removing the motor, it dawned on me that what I may have been hearing was bearing noise. I peeked into the oil level window and noticed it was DRY. She had no idea she had to put oil in that too. [img]i/expressions/face-icon-small-smile.gif[/img] I wish I would have thought to look there before I pulled the motor from the bike (live and learn). I'm now thinking that maybe filling it with oil may have stopped the rattling noise I was hearing.

Is that oil level window only for transmission level? Or is it crankcase (bottom end) and transmission combined? Would having no oil in there cause a rattling noise?