Needle & Seat Some of our kits have two sets of needle & seats. One will be spring loaded and the other will not be. Try to use the spring loaded whenever possible, especially on off-road vehicles. The spring type of needle & seat keeps the float from bouncing on a rough road, which will allow too much fuel to enter the float bowl.What is the size of the vacuum advance port located in the throttle body?The vacuum advance thread size is 1/8" FPT (female pipe thread), same as the fuel inlet thread.
We have run into a few older YF carburetors that use a shorter needle & seat assembly than what is provided in the carburetor kits. We have added an additional needle to our kits that will take care of this particular problem. This extra needle is included in our basic **YF kit K1111** and our **YF premium kit PK105**
https://youtu.be/BQrCkFq1Ik0?si=WNpX5c_LqkTcJmvn
We haven’t seen this needle sold in anyone else’s kits, so if you got your kit elsewhere and you’re having trouble matching your needle and seat, you may need to purchase one of these.
Some YFs will have an old style needle and seat that has a stem and used a filter, these are no longer available. Use the new style needle and seat that is correct for your carburetor number, making sure that the overall length of the seat with the needle in place matches the overall length of the old seat/needle assembly minus the stem.
