|Deciding which principal jets to purchase to tune your carburetor tin can exist a difficult task. You may not know what jet size would exist a good starting indicate for your combination. Why buy a agglomeration of main jets based on a guess when you lot may not always utilise them over again? By drilling out your stock main jet to larger sizes you will be able to narrow downwards what jet size your carburetor needs.|
You will need a numbered drill scrap set. Nosotros purchased this gear up from Harbor Freight. The brass chief jets are piece of cake to drill so you tin can get by with one of these inexpensive drill bit sets.
The commencement matter we practise is match the stock main jet to its corresponding numbered drill flake. If your stock main jet is a 100 (stock size in a 22mm Mikuni) you will notice this jet size falls between the #62 & #threescore drill chip.
|Run the engine with the stock main jet and take a plug reading. If it’s lean and you need to increase the size of your chief jet, drill the jet out with the next size larger drill bit, which in this case is the #sixty bit. Run the engine over again with the drilled out main jet and accept another plug reading. Repeat this process until you get a good plug reading. Run into our “Carburetor Tuning” section to acquire more nigh plug readings. Do not skip drill bit sizes because once you drill the main jet too large, you cannot become back to a smaller size.|
|You lot should use a drill press for drilling your main jet. You will need a vice with jaws that will hold the chief jet perpendicular to the drill chip. You practice not want the drill chip to enter the master jet at an angle because it could create an oblong hole in your jet.|
|In one case you lot drill the main jet to a size that gives y’all a good plug reading you can utilize the chart below to determine what size the jet is. In the photo to the left you can encounter the drill flake measures 1.19mm. This means we take drilled our stock primary jet to the equivalent of a 119 main jet.|