Smaller jet gives more midrange?

[Alberta EX]

I talked to the Honda shop today and they told me they put a 146 main jet in a 400EX with a K&N and a White Bros Slip-on and it smoked a stock 400EX. I think the stock jet is a 148 so how could a smaller one make it go faster???? We are at 3000'...Could some one explain this one to me?. He said you can add 9% to the jet size because of the altitude...146 @109% = 159.1 Does this sound right?

[JhallettEX]

Read what you wrote and think about it again. You think that the aftermarket exhaust and other mods had anything to do with it?

[Blake24]

ya i doubt it was all the 146 main jet and not the pipe/filter......obviously if u let a machine breath it will run better........lmfao........


hey guys think if i go with a 125 main jet in my stock 400ex i can smoke heavly modded shee's in the dunes..........

:huh :huh :huh :huh :huh :huh :huh :huh :huh hahahaha

[Alberta EX]

The POINT was, It was a 146 main jet not a 160 or 170 like everyone else here talks about having. This is the first time I heard anybody talking about putting in a smaller jet to make a bike go faster.......That is the point I was trying to make...

[JhallettEX]

Ummm, OK. You need to spend a little more time on here reading and learning, ***EDIT****. Good luck!

[Alberta EX]

I am reading and learning, however I am getting conflicting information on the jet sizes question. Could someone out there answer my question without a smart***** answer? The guy at the shop says the larger jet will only help the top end, I ride on trails where I need midrange and his experience is that a smaller jet is the way to go.....THAT IS MY QUESTION,AGAIN