Don't confuse income tax with sales tax. They are two different animals.
What you are describing is a sales transaction. If you are in the 'business' of selling (gears or anything else), then you should already be registered with your state and have sales tax reporting requirements. I would expect your state to require you to collect the sales tax from all sales transactions with customers who are not tax exempt. In turn, you send this money to the state along with some forms. Please keep in mind that some states do collect sales tax from tax exempt institutions so you really do need to know your state's regulations. If you think you fall into this category, find a CPA to speak with.
If, on the other hand, this is a rare and isolated sale, then it is possible that you have no reason to report this sale to the IRS.