Use a 10w-40 motorcycle or atv oil mean for wet clutches. The cheapest I have seen is by Valvoline. You can get it at AutoZone or Advance Auto for about $4 a quart. Your 200 will only take about a quart and the 250x will be around 2 quarts.
I ran the mobile one synthetic for a while then the price went up to the same as amsoil and i changed over to amsoil because i get a good deal on it from a local shop. Amsoil seems to hold up a little better over time.
I recommend AMSOIL Formula 4-Stroke Synthetic. It withstands the high temperatures of ATV's - resisting heat and thermal breakdown, keeps engines clean and controls oil thickening to provide excellent operating efficiency, and is also wet clutch compatible. I run this in both my 250r and 400ex.