I have an 09 450f with an fmf powercore 4 slipon with a twinair air filter. The next mod on my list is a fmf megabomb. I know i will have to jet the bike since I luckily slipped by with the stock jetting with the slipon and air filter. What would be you guys best guess on what i should do with the jetting after I get the megabomb. I live in central Pa and ride from spring till late fall in temperatures ranging from 55 to 90 degrees F? Also I am around one thousand feet above sea level. Any help is appreciated.

I ride from 2700 to almost 6000 feet.

Last fall, I installed a PMB endcap/spark arrestor which helps the stock can a lot, and also installed the Ti Megabomb header. I raised the needle (lowered the clip) one position and was pretty happy. When it got cold out, like around 40 degrees, it was lean at idle, like almost 4 turns out on the fuel screw to get rid of the hanging idle. It was great in the spring and probably a little rich at low RPM in 90 degree weather in the summer. This fall I finally installed a 48 pilot and it is almost too rich at idle, at least until it got below 50 degrees. I am going to put the needle back to stock before my next ride.

Summary: I will put the 45 pilot back in in the spring with the needle in the stock position, and next fall, install the 48 with the needle in the stock position. At your elevation, I would put in the 48 pilot and try dropping the needle for best throttle response, maybe go with the bigger main also. I'm planning to put the bigger main in for a desert race I'm doing in Febuary and see what happens--100 miles of sand wash:bonk:.

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