Horsepower improvement with needle shim

[Traumahawk]

I know that there are several people on this forum that have shimmed the needles in their carbs. Does anyone know how much of a horsepower increase that they had? For instance putting the bike on the dyno before and after it was done? Or has it just helped the drivability?

I have an 07 (with slip ons) and changed the jetting to 147.5's, and am just kinda curious if this will be an improvement (the needle shims), and how much (typically).

Also...how much should the needles be shimmed? Ive seen anywhere from .032 to a max of .040. I know that at .040 you might run into issues with the needles hanging up because of the plastic screw.

 

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I've never seen any HP figures before/after shimming the needles. I can't see it making much of a difference as a dyno runs are measured with the throttle wide open. When the throttle is wide open, the needle is fully removed from the main which means the needle has a very minimal impact on this part of carburation.

Shimming the needle is for driveability and mileage. Most of your riding is in the "midrange" which is needle territory. You want to drop the needle as low as you can while maintaining good driveability.

 

[Traumahawk]

Well here is a pic that I found on here to shed some light on it....and thanks for the reply. LOL...Im still having to learn that these carbs aren't Holley's or Carters

 

[one2dmax]

Don't look for a HP gain so much as driveability. If you're rich or lean then the washers getting you in a more ideal a/f range will help that (but again it's going to be difficult to pinpoint a number to it).

Sean

 

[Lew L]

My needles are shimmed 0.025" doing most of my riding at over 5,500ft is part of the decision to keep the shim thin.
Lew

 

[m-cman]

On my first Max I shimmed the stock needles with Dale Walkers shims, installed K&N filter, remover the "T" and had Jardine slip-ons. The throttle response was much better and the initial surge of acceleration was greater. Never had to use the choke again either. (Not that cold here though). I could snap open the throttle at low speed in first and pull a small wheelie. Never did that stock.

My current Max is completely stock.

 

[Traumahawk]

Well when I get home, I will shim the needles...and see what kind of improvement there will be. Oklahoma isn't that elevated, so I will try to get mine around .030 to .035. Thanks for all of the replies.