let’s compare a carburetor stock slide needle the stock slide needle that has been trimmed and a tapered slide needle but first let us look at how the fuel flows see how the fuel flows from the bottom to the top the fuel flow is restricted by the needle the red dots show where the restriction is at the needle the needle position is determined by how much throttle you give with no throttle the needle is at its lowest position restricting the fuel flow the most giving more throttle will raise the needle allowing for more fuel let’s place the different needle side-by-side the needle shown are at low rpm range the far left is a stock needle the needle in the center is a shimmed stock needle and at the right needle is tapered as you can see the stock needle at the left restricts the fuel flow more compared to the other two needles the shimmed needle and tapered needle allow for more fuel delivery there is virtually no difference between the shouldn’t stock needle and the costly tapered needle let’s compare at mid-range rpms admit range rpm we see the same behavior the stock needle restricts the most whereas the shipment stock needle and to the tapered needle allow for more fuel delivery again with no real difference between the shipment stock needle and the tapered needle now let us take a look at the high rpm range is expected the shimmed needle and the tapered needle provide equally more fuel here we can conclude that a shim stock needle and a costly aftermarket tapered needle provide similar increased fuel delivery next we need to look at the main jets since we allow for more fuel going through the needle we need to supply more fuel to the needle let’s compare a stock size main jet with the larger main jet to the far left you see the stock size main jet restricting the fuel flow to the needle the stock size main jet will not allow for enough fuel especially at high rpm when the needle is in the highest position the image next to me shows the use of a larger main jet the larger main jet supplies enough fuel to the needle even at high rpm a main jet that is too small will cause a lean condition and a main jet that is too large will cause a rich condition especially at higher rpms it is therefore very important to use the correct size of main jet the carb jet gets jet get calculator will determine the correct main jet size to be used let us compare the carb jacket jacket with a tapered needle jet kit we are now looking at a shouldn’t stock needle with calculated main jet size the size of the main jet has been calculated to have the optimal size so that only one main jet is needed this means for you that you only have to work one time on your carburetors next let us look at a tapered needle jet kit these kids come with several main jets of different sizes it is up to you to find the correct main jet size this means you will have to work on the carburetors multiple times so what do you think will work best for you another important part of fuel delivery to your carburetors are the pilot jets pilot jets or idle jets our most effective at idle and lure rpms to the far left is the shouldn’t stock needle with calculated main jet and next to me is the tapered jacket with multiple main jets the carb jet kits jacket includes a larger size pilot jet allowing more fuel delivery in addition to the fuel delivery through the main jet and Chim needle the tapered kit does not include a larger pilot jet making this jet less effective at idle and lower rpms the carb jet kits jet kit calculator will determine the correct main jet size the number of shims to use under the size of the pilot jet the calculated combination of the correct sized main jet the shimmed needle and the larger pilot jet will give you the best value in performance installation time and price you can find the carb jacket calculated jet kits at the link on the upper left corner now you see a large selection of motorcycles find your motorcycle on the list to proceed using the jet kit calculator

18 thoughts on “Shimmed Stock Needle versus Tapered Needle”

  1. got on your web site and tried to ask whether or not you service Suzuki motorcycles.  No answer.  No way to send an email with questions.  If you cannot answer this simple question on your web site, what good is it?  What good is this video?

  2. ..There are ONLY 2 reasons to change the "jetting" of your bike or atv is: 1 = Altitude change of 500 ft. or more. 2. Engine and/or exhaust modifications.

    The correct jetting is determined by spark plug readings.ONLY!!–. this "kit comparison" is NOT ANYTHING any really good "modified engine builder" would consider using,,,, SORRY. they are just wanting to sell you something kiddies..IMO!
    .. If you have added an after market exhaust system or after market head (home mechanic stuff) … or you have paid someone to port your cylinder, YOU MUST have someone that can read a spark plug correctly jet your engine!!.. or prepare to become great friends with your dealer and NOT your money!!
    Someone that CAN read a spark plug CAN tell you 3 things: 1: If the timing is off enough to cause a problem. 2: if the oil mixture is too rich or too lean (EITHER of these condition WILL MASK proper jetting!). 3: Proper fuel/air ratio for performance and engine longevity.

    PLEASE… do not make "jetting" something you want to do because of someone that wants to sell you something or does not provide you with more intimate knowledge of how a carburetor works.. this is a very over simplified-short of details,confusing, non-helping dribble fest….
    ……in my 45+ years of 2 stroke racing engine experience opinion.

  3. I can NOT listen to these terrible robot voices. I can't even go far enough into the video to see if it's god info or not.

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