cobraR, going to a 50:1 oil/fuel ratio will only RICHEN your Air/Fuel ratio (due to the higher spec. gravity of the oil). So, if you run 50:1 you will only aggrivate your problems, and possibly promote engine wear.
I suggest that you read Eric-Gorr's jetting guide (stated above) and get to work! As to my opinion on your oil/fuel ratio, I would be running at least 32:1 in your bike, maybe more if you race hardcore MX or something. A good rule of thumb is the higher the engine revs, the more lubrication it needs.