No, not that bag of caps and stems your buddy has brought on your annual camping trip. Your tires ability to hold air depend upon the valve stem cores and caps. These tiny items make a big difference with tire performance.
First, we will look at the valve core and all the details inside. Valve cores could be brass or stainless steel – either is OK. Looking at item #1, that tiny core spring is all that holds the air in your tires. This spring has a lot of work to do: fighting off centrifugal force to stay fully extended at big highway speeds, and keeping tiny grains of debris out of the seal. We have found that at higher speeds for a long period of time, this spring may fatigue allowing air to escape.
The next item on the valve core is the seal (#2) around the body. You may have seen many colors of these seals, but for a tires or tubes, only the red or black should be used. The black is standard, the red is high-temp rated, and all of the other colors are for specialty use (welding tanks, hospital use etc.) and should not be used on your motorcycle. We’ve also seen the old style long stem valve cores. These have the potential of getting bent while riding. If that happens, they will no longer seal correctly, and will also become difficult to remove. They shouldn't be used on your motorcycle either.
Looking at the tire caps, it is important to have a good cap with a seal for each tire. The standard plastic caps are OK when they are new, but will warp and crack over time, and will no longer make a good seal to keep air in. We recommend metal caps that have a seal inside, which prevents air from escaping as described above.
Using the proper brass or stainless steel valve core, with a red or black seal, and a metal cap with a seal inside is the best way to protect against losing air from your tires while riding.