I went out a got a K&N filter charger kit and HMF slip-on muffler and was told to up the main jet alittle. My stock main jet was a 122 and I went out and got a 125 and 128. It starts good, idles good, but when I hit the throttle fast it dies out and at about 1/4 throttle it runs rough. Giving it a nice steady rev it runs good. It does all this with all three jets..... so I guess my question would be, should I get a bigger jet and would messing with the idle adjustment knob help any (I tried to mess with it with 1/4 adjustments and still nothing)? I haven't even taken it out for a test run..... I live in a residential area.

Maybe I should get a bigger pilot jet

Contact Woodwardspecialities on this forum and get him to order you the Honda HRC jet kit for your 450R. Your main is much too small.

Hi, I have done the same mod on a bunch of the 450r's. You are way to small on the main. You need to be in the 160 range with the main. Shoot, they need a 140-150 range right out of the box when they are stock. Honda trys to set them up super lean for emissions I guess?
Take care....

Thanx guys I'll try out a bigger main jet...... HRC jet kit is going to be my best bet.