Spices - You can become wealthy as HELL, and your modern day clothes can easily make you seem like some foreign merchant, so can get you people interested. You DO need to sell those spices fast, however, else you WILL get robbed
Motorcycle - As others have said, you can get it to run on grain alcohol once out of gas, but that's not the real prize with it. The real prize is using your new found wealth to get smiths to make more engines, using that as a blueprint, and essentially kick starting the industrial revolution. Mind, this IS going to be used for war, so prepare to become a war mongul
We may be young at heart (emotionally), but we are old at heart (physically)