CRF450 - Hard to Start with BigGun Exhaust

I just installed a new race system from Big Gun. I jetted the bike according to their recommendations, which is the stock 42 slow jet and a 175 main with the stock needle in the stock clip position. I now have to start the bike without using the choke by blipping the throttle a couple of times, then kicking it over a couple times and repeating this process until the bike starts. It seems the choke (with no throttle twists) is just flooding the bike. Also, I no longer have to use the hot start after the engine is warmed up. All I have to do is kick it once or twice and it fires right up. Once running, the bike runs fantastic from bottom to top. I am in Florida, and the temperature does not seem to make much of a difference, it is the same starting procedure.

Could this be the slow jet or fuel mixture screw adjustment?

Yes, try turning the fuel screw inwards to lean the jetting at closed throttle and idle.

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