Now, for easy starting it’s best to have the lowend a little rich and it will four-stroke a little.
#Walbro 5 4993 parts diagram full
When this is done right, you will be able to set the throttle in any position and it won’t four cycle, plus you will be able to transition from idle to full power without any hesitation at all. Open up the lowend needle just enough to eliminate the bog or hesitation. Now, from full idle begin to throttle up until the engine starts to bog or hesitate. Keep doing this until you reach full idle. Now lower the throttle more until it “four cycles” again, and adjust the lowend again. Adjust the lowend needle until the “four cycling” barely stops. If the topend runs OK, then slowly pull the throttle down until the engine begins to “four cycle” hold the throttle there. Should the engine go lean, open the lowend needle slightly, if this dosen’t work you will have to adjust the needle valve inside the carb (will explain later). Leave it wide open for about a minute to see if it changes any. Let’s set the topend first since it’s the easier of the two. Choke or prime the motor until the carb is wet. Don’t confuse fuel/ air mixture with fuel/ oil mixture which refers to how much oil gets poured into each gallon of gas.įirst, screw in both lowend & highend needles all the way then unscrew to about 1 3/4 to 2 turns out each. Screwing them in reduces fuel flow which leans the fuel/air mixture. Unscrewing the needles on this carb increases fuel flow which richens the fuel/air mixture. The highend needle trims mixture at mid-range through full power. The lowend needle refers to the one that trims idle mixture mostly and affects mid-range mixture somewhat. The most relevant parts have been included here in case the original gets relocated.
See also membrane carburetor overview, Buyers guide for Walbro Carbs and Rebuild Kits Adjustment and correction of problems found on Walbro Carburetors
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