My 230 has a stock engine. This bike has never bogged when you open the thottle. I have changed nothing on the bike since last fall. I ran it several times over the winter to keep things moving. I have checked the adjustment on the mixture screw and it is correct. Normally this type of problem may require a needle clip adjustment on some other bike, but in the case of this bike it wouldn't be needed. It has a new spark plug and air filter. So what other ideas do you have as to why it is bogging when I open up the throttle? Thanks.