i would like some help as i dont know much about mxers i recently replaced my piston and got a v-force3 for a yz 125 2001 model it fouled a plug today which it wouldnt of normally done when i started it bogged out nearly straight away i took out the spark and to my expectations it was oily i cleaned it off and it starte up ok but i had to throttle in a bit to keep it from stalling. i run it on normall premium unleaded as i cant get hold of super unleaded which is what i was told to use by the lad i got it off but my mechanic says i can put in this stuff that adds to the petrol for the life of me i cant remember what its called but he told me it makes the petrol igher quality or something similar can anyone tell me what would be the best thing to try ie jetting settings (baring in mind i dont know much about those so i might need a detailed explanation sorry) or is it my fuel (and yes i use the correct oil mixture 125cc to 5 litre) or is it that my mechanic dint re jet the bike after v-force was installed cos on the packet it says fit larger main jet with this product (whatever that is im sorry for mylack of bike knowledge but i have fidled with things that i know nuthin about before and broke them i am not gonna do it with my crosser thanks