[tjwalters]

I have an 08 450x with a vance n hines xcr slip on. Put the emissions block off kit on and did the air box mod. The bike has lost alot of midrange power and does not run nearly as good as it did stock. I have not done any jetting or other mods yet. I am looking for advice on how to get it to run great again. I live in pa and normal riding temp varies from 55 to 80 degrees( elevation i am not sure can find out if nessasary).This bike ran unbelievably good and i just want it to run that good again or even a little better if it is possible. Will appreciate any advise.

[450xdirt]

Well you are getting air in and air out, but you need to get more fuel in, that is where the jetting kit comes in. You have a couple options:

1. NCVS needle with larger main jet (165-170)
-Honda dealer

2. JD jet kit includes two needles Hot(red) and cold(Blue) and i think 5 main jets varining in sizes up to 170. This kit also gives great step by step directions. -JD Jetting

Both set ups are good and will do a great job of getting more fuel into your engine.

Also removing the backfire screen helps a lot to get more air in. Twin air makes a great kit.

Hope this helps.

[tjwalters]

Thanks I will try the jd.