As long as the motor chain is a standard 410 bicycle type chain, you can get a link buster in the bike section of Walmart, usually on the same isle as pedals, inner tubes and mirrors. Pop the master link and start off with removing a single pair of links from the end, reassemble & adjust the plastic tensioner wheel up to take up the chain slack. If your clever enough to keep the clutch engaged and free the master link at the bottom of the chain, you may not have to completely remove the chain or have to rethread the chain thru the motor sprocket. Keep in mind that chain grease gets nasty dirty, so dress accordingly and bring a rag & waterless hand cleaner such as Gojo or Fast Orange with you before you even start, or learn to live with permanant stains on every latex painted surface you touch.
Or ask your local bike shop to shorten it for you.