Jetting ? for a stock 08 XP 154

[birdie]

I was just putting her away for the summer and thought I would see
what size jets are in there
They are 480's
My question is can a guy go a little lower to 460-470 and get any gains
of performance

I have a stock engine

Opinions or facts would be appreciated

Thanks
Birdie

 

[MARCUSO]

How do your plugs look? That is the main thing.

I don't think leaning out your jets will show anything noticeable exept putting the motor more on the "edge"

 

[trinitypowder]

I'm on 480's with my SHR860 at 10k and up with '07 needles in the 4th clip from the top. The 470's didn't quite pull as good on top as the 480's. I tried 500's and that was WAY too much. I say better safe than sorry! I also have MONSTER holes in the back of my airbox.

 

[JamesS]

I'm running 440 main jets and 9EGY2-58 needles with the clip in the middle (RKT head & "The Thing" can), my sled pulls hard with this setup. I ran the stock 480 jets and put the clip all the way to the top (leanest) and it ran super rich. The best thing a person can do is to buy adjustable needles!

 

[07rev800R]

I'm on 480's with my SHR860 at 10k and up with '07 needles in the 4th clip from the top. The 470's didn't quite pull as good on top as the 480's. I tried 500's and that was WAY too much. I say better safe than sorry! I also have MONSTER holes in the back of my airbox.

monster holes.... show some pics....

 

[trinitypowder]

I'm too lazy to go get pics! Instead of 2.5 flowrites, I have two 3"X4" square holes with silk over them.

 

[DWHalverson]

With silk. I like that ? How many thread count is the silk ? Good idea. Stock box gets kind of choked down at times.

I run a big hole in the top of my air box and ya know what goes in there? Lots of CFM under lots of PSI!!

I'm too lazy to go get pics! Instead of 2.5 flowrites, I have two 3"X4" square holes with silk over them.