Oil smells like gas - if correct would mean carb is probably leaking. Fuel valve could be leaking and/or float height could be incorrect or the float needle valve is still leaking. Bike starting with no choke - if all jetting is stock, o-rings and seals are in place and undamaged mixture screw is only 1 turn out - also implies possible fuel leak or overflowing float bowl. Due to modern fuels, the spark plug will tell you nothing unless it is super, super rich. Put the snorkel back in. 1998 would be EPA lean and would probably have a slight bog at low throttle / low-to-mid rpm until thoroughly warmed up. Going up one size on the pilot jet and/or switching to the adjustable needle would probably cure it.