My Austro Diamler is an excellent bike. It handles nice, rides smooth, always runs and looks like Robocop turned into a moped. About two months ago I was riding it to Moped Monday. Headed down a dark and dangerous street, my headlight didn't cast enough warning and I hit a huge pot hole. It banged very loud. I heard a scraping noise, and look behind me to see my tail-light, still lit, dragging behind me bouncing along the road, and then suddenly it lets go and becomes black as it slides to a stop. AD's gas tank is plastic and great, except for the fact that the only thing that holds the tank under the frame is the tail light. I know, pretty stupid. Perhaps the rear fender played some role, but I dont' know, I've never had one. With the light gone, I realize the gas tank is dragging on the rear wheel and now my moped is very loud. I get the light, put it in my bag, reach behind me with my left hand and hold the gas tank up while I drive home with the other. I put it in time-out, not because the moped misbehaved so much, as I wanted to punish the engineers. Last week I zip tied the tank on and took it for a ride, and it was still incredibly loud. I tightened up the exhaust cap screws, but they were both snug. When the motor was running, I could feel exhaust with my hand. In spite of the air leak, I rode this bike to Moped Monday last week, and every time I hit a bump I was relieved to see the pipe was still with me. I didn't really think about the danger involved until I was driving at 35mph down a bumpy street, imagining the header snapping clean off, throwing that big metal snail right under my rear wheel. I pulled the pipe to inspect it and here is what I saw.
The subframe pivot must have pushed the circuit pipe down low enough to connect with the pavement when I hit that pot hole, cracking my header. I'll take this pipe down to the shop and weld it up sometime next week. I'm not sure if I can get a TIG torch in there or not, we will see.
When assembled and run, the head and piston made contact, which, encase you are new to mopeds, is a bad thing. I took it down to the shop today, and with the help of M.M.N., I was able to watch and go "uh-huh" while he explained complicated theory about squish band, compression, precision machining and potential power differences based entirely on making the head fit correctly for the application. The head is now milled flat (on the mill) and then a new squish cut in via lathe. 
No clearance problems any more, and a heck of a lot more compression (potentially). Also, take care to notice the size of Naz's left nostril, through which he inhales massive amounts of oxygen, which I think is what fuels his genius brain. I look forward to finally putting this engine on a bike and running it now that I have my wheel back from John Elkhart who borrowed it for a bit.
