Modern two-stroke motocross and off-road bikes seem to come jetted far better than ever before. The only drawback is they seem overly sensitive to change. In most of the cases we've seen, even one clip position is often too great a change. As a result, we find ourselves adjusting the air screw for changes in temperature and altitude. Zip-Ty Racing makes $21.95 billet-aluminum, anodized air screws to replace the stock screws in both Keihin and Mikuni carburetors. The difference is the stock screws demand a tiny blade screwdriver, whereas the Zip-Ty screw is longer and has a knurled knob at the end. The screws are not so long that they're vulnerable to damage but are easy enough to reach and adjust with your fingers. If your ride takes you up in altitude or the weather suddenly grows cold, you can easily fine-tune the carburetor setting without even removing your fanny pack. We have one in a Honda CR250R's Mikuni, and it installed in seconds and works great. This is probably not a necessity but is certainly convenient.