Carb Jet Needle Adjusting

[scooterlover]

Adjusting your jet needle makes your engine run leaner or richer. If your plug electrode is black and sooty looking you're too rich. If it's bare or glazed you're too lean. It should look a light tan or grey.Here are some common sense guidelines and tests from our friend Alleyoop for determining if your carb is running rich or lean, and a spark plug chart.

First remove the top of the carburetor:


Remove the long spring:





Then the diaphram, vacuum slide, and needle; be careful, the diaphram is somewhat delicate:






Next, use a phillips screwdriver to turn the screw at the bottom of the tube to release the needle, parts may vary considerably from carb to carb so please take note of yours!:




This is the plastic retaining nut with it's spring on this particular carburetor:








Turn the diaphram carefully upside down and remove the needle taking note of the retaining parts and their order, again, they may vary from these:





Carefully reposition the clip up or down as needed, moving the clip down richens the mixture by pulling the needle up higher and releasing more fuel. Moving it up leans the mixture by holding the needle farther down in the jet:







There's been some confusion in the past about what direction moving the clip "up" or "down" means. Up is higher and closer to the flat top of the needle and away from the taper. The following diagram shows how moving the clip affects the mixture:









Some needles do not have a clip and adjustment is more problematic. In these cases members have used different sized washers to change the mixture. If you need more assistance, ask in the GY6 or 250cc sections. Reassembly is of course in the reverse order, make sure the small tab (red arrow) on the diaphram fits into the small notch on the carburetor:








Put the cap on with it's tab (red arrow) oriented on top of the diaphram's:









Time to crank it up!