Too lean, and the bike will run flat or have a flat spot in the powerband. If your main is too rich, the bike will sputter and surge as it tries to burn all of that fuel. The main kicks in at half throttle and takes over metering duties as you hit full throttle. Your main jet is probably the most talked-about circuit, and it's as critical to get it right on a four-stroke as with a two-stroke. Pinging can also be caused by too little octane or winterized fuel (oxygenated, blended with additives), so keep in mind any fuel changes if your bike suddenly starts detonating in otherwise 'normal' conditions. If it's too lean in this area, the bike will feel really flat and down on power, but will respond quickly to changes in throttle position. Too rich jetting (too much cutaway, needle positions too high, too large a needle jet) can make your bike lunge and hard to control. Due to the hassle of making changes to these circuits, these are the most neglected areas of tuning.

Your slide cutaway (or throttle valve) needle and needle jet will all affect your bike's acceleration from one-quarter to three-quarters throttle, and this is the most important area for off-road riders, since we spend the most time at these throttle settings. Even though they may differ wildly in size, shape and design, all four-stroke carburetors have the same basic parts or circuits. Your engine is basically an air pump, and your carb meters how much air and fuel are sucked into that pump.

Best venturi carb shape motorcycle