When you shim the carburator needles you will eliminate that slight
hesitation you get on take off, when you go from off idle to wide open
throttle. We used 20,000 (thousands) thick shim washers for this
project. I got a bag of shim washers from Radio Shack for a little over
$2.00, with enough shims to do 10 ATVs.
Remove your carburator air box.
Remove
the 2 black side covers to reach the needles. This will allow you
access to remove the needles, and to install the shim washers on them.
Remove the 4 screws on both side caps. Be careful you don't loose the springs or any other parts when you remove the caps.
Remove
caps slowly, and set aside. You can almost pull the needles out with
the spring, that is attached to the retainer clip that holds the
needles in position. Be careful that you remember what order every part
goes in place.
I pulled the springs out with the cover caps, and left the rest of the parts in place to be removed next.
Notice where the seal fits in the grove at the bottom of
the carb..Make sure when you re-install the seal that it lines up
correctly in that position.
Be
careful if you yank on the springs, you will loose some parts. Put your
hand over the seal and gently pull the springs out and set them aside.
Note how I put a towel over thecarb openings to keep out any debris from falling in, ruining your day.
Slide out the vacuum piston from the carb.
Pull your slide clear of the carb. You can see the
needle sticking out of the end of the slide. Be careful not to drop any
parts now.
All our parts lined up ready to re-install into the carb.
Shown
is the needle with a 20 thousands shim washer slid on the needle. Be
careful the washer doesn't fall off the needle when you insert the
needle in the slide.
Needle & Shim placed in the slide. Now to slide everything into the carb without dropping any parts.
Slide
everything in place. I used my finger from the top to guide the needle
in place. Don't force it, the needle needs to go back exactly where it
was before in the slot.
Note the needle with the shim installed. Push everything
into place slowly, lining up the needle in its proper position. Also
remember to position the rubber tab at the bottom grove in the carb.
Re-install
the springs with the retainer clips. Remember these retaining clips go
over the ends of the needles and hold them in position.
Re-install the caps, being careful not to kink the springs when you position the caps over them.
Re-install
your air box, and check for gas leaks. No sense ruining your day after
all this work. Put everything back together and try it out, and see if
your ATVpulls better for out of the hole!
Note:
Pros:
This is a twenty minute job, if you do this project at the same time you re-jet your carbs ( for the new exhaust or cdi you have just installed on your ATV).
I really noticed a difference in my Prairie 650 when we did this
mod. I am still doing the initial testing on the Prairie 700 mod, and
time will tell.
Cons:
Just the inconvenience of getting your carbs prepped for the mod. The actual mod is simple to do.
Bottom Line:
A very easy mod to do and it gives you a little better snap at take off. I would recommend doing it.
