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Shimming the Needles

41192 Views 176 Replies 52 Participants Last post by  Navy Ninja
Sorry for the delay on this one guys, I know a few people have been waiting for me to post this.

"Shimming the needles" refers to the needle valves in the carburetors. The needle is just that..a piece of metal that tapers down to a point at one end. It sits in a hole that is also tapered. As rpms/load vary this needle moves up or down out of the hole, increasing or decreasing fuel coming out of the valve. What this mod does is starts the needle farther up out of the hole, meaning more fuel, and a richer mixture. This is needed if you install exhaust, or an air filter, however, I would recommend this mod even on a STOCK BIKE. My bike has always been a little hesitant to start, and I could not even free rev it until it was warm. After shimming the needle valves my bike starts with no issue, now I don't even have to use the starting enricher (what people refer to as the "choke", even though it isnt one :p).

Ok, so how to do it;

What you will need
  • Stock tool kit
  • Phillips screwdriver
  • Small washers*

*A note about the washers: The washers I used were .025" Thick. They had a 1/8" hole in the middle. Sorry I was boneheaded and didn't measure the overall size> It doesnt matter really as long as it fits inside the spring retainer (read on).
Step 1
Remove your fairings. If you need help with that, read this post http://www.newninja.com/how-to/removing-the-fairings-(plastic)/

Step 2
Remove the seat. 1 bolt on each side hold it on.

Step 3
I will update this step next time I need to remove my tank ;D.

Remove the fuel tank. Sorry, I had an issue with the camera so no pictures of this process, but it is simple. Loosen the clamp and remove the fuel line going into the carb on the left side of the bike. Put the line into a container. Turn the fuel valve to "PRI" and the fuel will flow out quickly. While this is draining unhook the 3 emmisions lines at the front, left of the tank. There is also 1 emmisions line hooked into a "T" underneath the tank. After all the fuel is drained, remove the 2 10mm bolts at the back of the tank. Now slide the tank back and lift up the back of it. Unhook the electrical clip for the fuel gauge, and pull the tank all the way off.
Step 4
Now we are at the point where we can see the carbs. Remove the 4 screws on the slide cover (black squares on top) with a Phillips head screwdriver.

Some of the screws can be a pain to reach so you may need to use a long screwdriver or an angled one.

Step 5
With the cover removed you should see something like this...

Now remove the diaphragm, needle, spring, spring retainer and slide all together.

Step 6
Take the spring, spring retainer (white plastic piece) and needle valve out of the slide. (Spring not pictured here)

Step 7
Now put the washers on the needle. I used 2 washers per needle, effectively raising the needle .050". You may use only 1 if you don't have any mods, or if you feel the need for even more fuel use 3. The washer needs to fit inside the "feet" of the spring retainer, so it cant be too large.

Step 8
Now put it all back together.
Insert the slide without the needle (if you do it with the needle in, the needle may get caught and you could damage it). The slide has 2 holes on the bottom. The one in the middle is for the needle, the other needs to be facing the engine side of the carb when you insert it.

Now insert the needle carefully, then insert the spring retainer with the "feet" facing downwards.

Then insert the spring.

Make sure that the slide diaphragm is in its grove, and will not be pinched by the cover. Install the slide cover, making sure you put the spring in the little "knob" in the middle. Careful when tightening down the screws for the cover, it's only plastic.

Ohh, and if this isn't obvious...You need to do this to BOTH carburetors, using the same number of washers on both.

This may seem a little overwhelming or very in-depth just reading it, but trust me, this is simple. I spent way more time removing the fairings and tank than I did working on the carbs. Just take your time, and remember how it came apart.

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I don't plan on much modding when I get my bike but this one sounds like it could be worthwhile.

But, how much does it affect fuel efficiency, and the actual ride?
Ohh yeah, I guess I should have put that in the original post...

The ride is WAY better. Low end feels like it gained torque (and the dyno sheet I'll post in a few hours confirms it). As far as gas mileage goes I have seen a small drop of about 3mpg. More torque down low means I don't wind it out as much in everyday driving, less rpm=less fuel, but at the same time, it is running richer down low than before, so it kinda equals itself out. The increased power down low is worth the 3mpg for sure though.
Thank you, very nice instructions. You made it very simple .
Sweet Nick. I am gonna do this on saturday.
The bike looks kinda cool with that fairing off
Nice work red thanks! This is on the definate list of things to do...


No problem! Glad you guys find it useful! If I could only do one thing to the bike it would be this... It makes such a noticeable difference.
Listen to the Admin man.!!
Mine were done last month and it really does make a difference.
will the dealership do this for you if you ask them? i am about to take mine in for the first service and i would rather just ask them to do it if it is something they will do.
I wouldnt think a dealership would do it. Not that there is anything wrong in doing it this way, but I think most dealerships look at this as the "ghetto" way to do it. Not that the jet kit does anything different with the needle...its just a different shaped needle instead of raising the stock one. IMO, this is easy enough to do, and it costs nothing, so I can't see why you would jet it unless you are REALLY doing some tuning on a dyno.
my dealer did it.
zartan said:
my dealer did it.
for free? or what was the deal on that one
not free :) Money was worth it since I have no tuning ability, just grunt stuff like oil changes...
I posted most of this before in Exhaust thread

The tuner did some needle adj and limiter adj. and one jet.
he did not use a specific kit he is a motorhead and understands what he needs to use on his own.

"It was about 200.00 of our lowly us dollar with some other work performed at 79 hour.
I had them install the adjustable clutch lever ( broke a bit trying to break the end bar loose. Needed an air impace. RED fricken lock tite.)
( lever from a 600, My finger reach is short, works great. I painted the lever black
also so I imagine a hour or so labor and some min. parts. He synced the carbs because they were way out of whack.
if there out of whack should that be a manufactures default or defec...so free? llol
Nahh..carbs will get out of sync when you tune them...or just over time from the vibration of the engine loosening the adjuster. I'll be doing mine soon...so expect another write-up.
After talking with you Nick, I am gonna shim my carbs this weekend. Try atleast, if my wife doesnt take up all the time and wanna go ride. haha
So for a Full AreaP, K&N and remove snorkle could you just shim or would a rejet and sync be the go?


Shimming would be fine for that. The bike is only too lean down low, its actually too rich up top. Shimming helps you down low and leaves the top as-is so it works out perfectly.
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