| it also depends on the oil you use. my bike likes shell r30 at about 30:1 but has a slight flat spot opening the throtle at 2/3 revs. tried castrol 747 love it 35:1 no flat spot, no fouling whilst idling. clean all the way. but is not the same for all bikes sugest to try a few diffrent brands depens on the mods on your engine. would stick to 30-40:1 RATIO. | 
