I learned to ride motorcycles on a retired military dirtbike.
Many years ago (early 90s) when I was flying C-141s I had, like most aircrew, a desk job for the time I wasn't out on a mission somewhere. I worked in what was called RED Section (Research & Equipment Development) and we were responsible for procuring any special equipment our squadron and SOLL crews needed. I managed to develop a good relationship with the local DRMO folks (they would feed the main DRMO office on a nearby base) and I would stop by from time to time to see what was in the scrap metal bin that we could use in the office.
One day I noticed a cammo motorcycle leaning against the dumpster and asked the guy about it. He said the AF combat controllers brought it to them, but since there were no records for it and no paperwork they couldn't send it to the main DRMO office, and it was going out with the trash. "Can I take it?" I asked. "Sure", and he helped me load it in my little Ford Courier. At home I discovered it was a Yamaha XT350, most of the lights were gone, but otherwise looked to be in fair enough condition. I had rebuilt some side-draft carbs on a Triumph TR4 in the past, and the ones on the bike seemed similar. This was all before internet so I pretty much noodled it and got it running (only one fire).
One type of alert posture we had as aircrews allowed us to stay at home but we had a 30 min response time to the base- so we couldn't venture too far or cross any draw-bridges. It was easy to spot us because we carried two pagers in a leather holster on our belt; one base and one commercial pager for backup. So I had two weeks at home to learn to ride a motorcycle, something I had always wanted to do but had never done. There was a big empty lot near my house that some dirt bikers used, so I would don my flight helmet, dark visor down, and ride out of the subdivision and cross the main 4-lane road through town to get to the lot. One time, as I was in the center lane waiting for traffic to clear so I could get across, I spotted my BOSS staring at me from his car. With the visor down though he had no idea it was me; just some guy in a flight helmet on a POS green cammo bike. The XT350 had only a kick-start lever, no electric start and I found that if I let it stall when hot it was a b**ch to get it restarted. I kept a can of staring fluid in the tool pouch for just that purpose.
One day I spotted another rider in the lot, with a real nice modern dirtbike. To my amazement he was also wearing two pagers, and he spotted mine; he was on one of the other alert crews. We talked about the bike I had and he gave me some valuable advice and tips. He also adjusted the clutch cable so that it was working properly. I dropped that bike more times than I could count, sometimes getting trapped underneath it and it always stalled.
Once I started down a narrow trail that led out of the lot, and it kept getting narrower and narrower until it was barely wider than the handlebars. I was getting nervous when it suddenly opened up and ended in some other subdivision. I needed to get the bike turned around because I was uneasy about getting home and to the base in time if the pagers went off, but the only way to get turned around was to cross a very deep drainage ditch and turn around on the other side. Taking a deep breath I eased the bike over the edge and gunned it into the ditch with enough momentum to make it successfully up the other side.... only to get entangled in the guy-wired on a light pole! After extricating myself from the one obstacle in 100 yards
I got turned around and tried to repeat it going back. This time though I had to line up just right so I could hit the tiny opening in the trees on the other side, and sure enough my nervousness bit me and I didn't carry enough smash to get up the far side of the ditch. I tumbled backwards and landed at the bottom of the culvert upside-down under the bike...in about 4" of stank water. It took easily 30 minutes to get out of that mess and get the bike restarted.
All good things must come to an end however. One day I decided to do a speed run down the road that serviced the industrial park alongside the big lot. There was no speedo on the bike but I had never had a chance to really open the bike up so I figured it was about time. The run down went well, but on the return the bike suddenly died and no matter what I did it would not restart. I pushed it home and looked it over. I jumped on that starter for several days until I could barely lift my leg, but it wouldn't start. I sold it to a friend for $100 and he figured out the magneto had quit.
Fast forward to around 2010 and I spotted a civ XT350 for sale and bought it. I relearned to ride here in the Pacific Northwest on that bike. I had to take a mandatory safety course on the base where I worked, and that was in March so it was always cold and wet. The rest of the class used the modern shiny loaner bikes and every day I showed up with my crappy looking XT, but I was the only one that could U-turn inside the box. I sold that bike a year later and still haven't replaced it. I would love to find a military KLR but I don't see them on the auction much.