My little brother just got a 250r with a FMF pipe and power core silencer and a k&n filter in the stock air box. It seems to be running a little rich the way it is set up now. I think it could be a little faster and it migth be the jets that make it lag a little. Does anyone know what the ideal jet size would be for his quad and set up. we ride a sea level.
Thanks

 

I used to ride my stocker with a 158 main with the lid and a 160 without at sea level with an FMF and a K&n filter. Just keep tuning and you will get it running sweet!!!

 

Where are you riding? I have an 86Rw/ a fatty I ride XC with a Uni filter ,Outer wears instead of an air box lid. It's jetted with a 148 main and the needle on the #2 position. All was good through the woods, but then we went to the dunes. I got in about half a day at full to 3/4 throttle. It was to lean for the dunes, I burned the exhaust edge of the pistion. Ouch. New pistion and another overbore. Always check the plug.