Another Jetting question, Do I need jetting?

[Red 99 400ex]

I looked through the Search archives.. but my question wasnt answered.. I have a 400ex. WB E-series and a K&N and Outerwears and I run the stock airbox with Lid. MY bike seems to run fine. NO hestitation except at LOW RPMs in High gears,(normal) it does sorta suck back when i let-off at High RPMs Cranks easy takes gas pretty fast in other words warms up quick. (it is summer) So does it need jetting I bought the bike USED with a K&N and Huge Holes cut in the airbox lid. It might have had a BIG GUN pipe.. stock one was on it when i got it.. There was a big gun sticker on the airbox.. I have not checked the plug yet though.

[hondarider2006]

yes you need to jet, unless it was jetted before you owned it. You need to do a plug test, and that will tell you where you are at. I am going to say that you are lean, and need to go up a main jet size or two.