The clip on the needle can also be moved to calibrate the jetting. Turning the screw out will make it leaner. Turning the air screw in will make the mixture rich at, and just after idle. Start with the air screw out 1.5 turns and the needle with the clip in the center position. If you need jets and can't find them, give me a call and I can help. It may seem like a waste of money, but you need jets to jet your bike. These jets will cost you between $30 - $70 depending on where you get them. Buy two needles- one leaner and one richer. Buy six pilots- three larger and three smaller than the stock jet size. What to Buyīuy six main jets- three larger and three smaller than the stock number.
We are going to buy a series of jets in both directions of the standard jets and you’re going to keep changing jets until you find the perfect combination for your riding style and riding conditions. Remember those sizes that we recorded-the main, pilot and needle jet. Hence the screw it all up method of carb tuning was born. I also realized that most of the people I was asking were as clueless as I was. FRUSTRATED!!! I began to realize that you can't explain how a carb sounds or feels. NOW WE'RE GOING TO SCREW IT ALL UP!!!! When I first started tuning carburetors, I would talk to other racers, call service shops, ask my friends, I even let my dad help one time ( one time!!!! ) All of this effort got me one thing. We've established our baseline jets and I'm going to assume that your bike is running fair. Lean engines will be slow to respond and at times will pop and backfire. Lean is heat and excessive heat destroys engines! Therefore, we have to be careful not to let our engine run lean for any length of time. Not that this means it's a good thing, but it doesn't have the same piston melting power as a lean mixture. Hear the difference? This is what a rich mixture sounds like. Start your bike and bring it to operating temperature. A rich mixture makes a very distinct sound and smokes excessively. Any more air and we term the mixture lean - Any more fuel, and we term the mixture rich. If you don't have the stock carb, you have no way of knowing what stock jetting is.
Your jetting should be fairly close and now you can begin to tune your carb. Set the float height according to factory specs and reassemble. Wear will appear as a ring or depression on the needle.
You can find the stock specs in your service manual or you can call your local dealer. If you bought your bike used, the jets may have been tampered with and jetting may be a long way off. Compare the sizes to the stock factory sizes. Inspect and record the sizes of the main, pilot and needle jets. Use the compressed air to clean all of the passages in the carburetor. Take care not to lose any of the small parts. The first step is to completely disassemble and clean your carburetor.
Main jets can be removed by a 6mm nut driver or a flat-head screwdriver. Compressed air is a must! You'll also need a small flat-head and a #2 phillips head screwdriver. You can also use it to clean power valves and other small parts. You can get the dip tank at any auto parts store. You'll need some carb cleaner or even better, a dip tank. When you’re done, you will know when your bike is lean or rich and you'll know what to do about it. It's time to get fuel on your hands and use your head. I can sit here and try to make this easy for you by giving you a list of jetting specs for your bike or I can get rich selling jet kits that I think will work, but the results will be the same, you will learn nothing. The best way to tackle a job or learn a new skill is not to cut corners, but to grab the bull by the horns and try to learn something. My method of two stroke carb jetting is aimed at training you to recognize when your two stroke carb needs to be adjusted and what changes you can make to accomplish the task. There are many informative articles on the net related to two stroke carb jetting and tuning.
You'll save yourself some time and money in the long run.Īll of these problems can affect carburetor tuningīasic two stroke carburetor tuning is a skill that should be mastered by anyone that has a two stroke bike or ATV. Take some time to go over the check list I've prepared. Before you begin your search for the perfect jetting, you need to be sure that there are no problems with your machine that will make it impossible to tune your carburetor.