I'd like to start by stating eBay is a great place to purchase new and used motorcycle parts.   I own a 1995 Honda CBR that I rebuilt from a wreck.  50% of the parts i bought to restore this motorcycle came from eBay sellers.  I would say in all i have bought over 150 parts through eBay.  In all those transactions I only had one small problem, I paid a seller two times for the same item.  With an e-mail letter to eBay, my money was refunded for the overpayment.  How many times can you say out of 150 purchases you had only one minor problem occured when buying from a local store or shop?  More than likely 1 out of 20 purchases we make at local stores ends up leaving a bitter taste.

Check the sellers feedback score and return policy before buying.  Also use the "Contact Seller" button to ask any questions you may have about the item that weren't answered in the item listing.  Also instead of buying the first one ( item ) you see, put a "watch this item" on it and keep searching eBay for more items just like it.  It pays to comparison shop, even for used and new motorcycle parts.

Are you worried you will pay for an item and never recieve it?  This RARELY ever happens and when it does it's usually just an oversight by the seller or a shipping delay.  The USPS and UPS shipping providers work very well in tracking shipments and provide a tracking number to see where your package/item is.  Also shiping insurance can almost always be purchased for $1-$3 depending on the cost of the item.  In the event the package gets were to get lost, you're covered by the insurance.  Again out of the 150 items I purchased to restore my motorcycle all the items/packages were recieved by me in a timely manner. 

eBay can save all of us a lot of time and money when it comes to buying motorcycle parts and accessories.