This is code for "I found another bike for less on Craigslist and want to buy that one instead"
I think we have a winner here.
Honestly, I have been in both situations before, both as a buyer who got something that wasn't quite as good as I thought but I had to deal with it, and as a seller who let the "guilt" get to me.
Let me tell you a story, a few years back I had an Acura Integra, nice looking car except for a little body damage. I tossed it on craigslist for trade and someone contacted me with another car. I met with the guy and made SURE that I explained everything to him. It needs this it needs that, etc. The guy drove it, brought his "mechanic" friend with him who was standing there telling him all the stuff it would need, clutch, exhaust, etc. HE decided he wanted to trade, so I went with it. I took his car and he mine, I went and got the title transfered, the tag, etc. About a month later he sends me a text and says "hey, this car won't pass emissions" I replied, "yeah, I told you that" I went on to say "I'm very sorry for the trouble but I did let you know about all of that before hand" he says "no, it's illegal to sell a car that won't pass emissions, give me my car back or I'll take you to court" he was half right but I would have won the case as he agreed to take the car "for parts" which makes the sale legal. Anyway, my wife told me DO NOT trade back, he took the deal, it's his problem. Well, I slept on it and agreed to be the nice guy and trade back, he had told me that he'd spent hundreds on the car trying to get it to pass emissions and since he couldn't pass he couldn't tag it and had no car to drive to work. So, I met with him, took my car back and as I pulled out of the lot where we met I noticed a HUGE cloud of smoke behind me. Welp, he had spent some money, new clutch, exhaust, all of that but he had BLOWN the rings! So, I now had a car that skipped, smoked, and wouldn't idle!! I sent him a message and advised that I would be taking his car back since he had destroyed mine.. His response? "F you, you traded a piece of sh*t car, you got a piece of sh*t car" In other words, he screwed the car and then me. My nice demeanor bit me in the a** on that one..
Moral of the story, if we make a deal, it's a deal. Too bad if you change your mind, the minute your name goes to paper or your cash goes in my hand, it's yours. I learned that the hard way and I will not be making that mistake ever again. It put me into a situation where I was having to get rides to work from my elderly grandmother because I couldn't drive my car when days before I had a perfectly fine one. That car I got back from him had taken me back and forth for months, thousands of trouble free miles, so I know it was him who did the damage.
In your case, block the guys number and don't talk to him again, that is HIS bike now. You have done nothing wrong and you don't owe him a single thing.