Synthetic oil in bike

what are the benifits in changing to synthetic in my 1977 honda xr75?

Same as in a car.  You will get a little better lubrication (mileage and power) but not much.  You will get longer life to the engine, but not all that much.  You will pay more, but not all that much. You may bet longer life to the oil, but I would stick with the manufacturer's recommended changes. 

I use synthetic in my bike.  Bikes tend to have wide ranges of heat and the synthetic stands up better under those conditions.

and i cleaned out those fins, it runs much cooler now, thanks

so… whats the best kind of synthetic to use?