I sure did! I had a heck of a time with the muffler! It wouldn't seal at the flange (2mm gap on bottom of flange) then after adapting silicone to seal it best I could, the muffler tip came off mid ride! I had to stand there, waiting for the tip to cool. lol. It would blow off at 17km/h after that, it became unusable until I went into an automotive shop, and thankfully the dude put nine tack welds around the tip, and it never came off again. I had that engine screamin doin 53.8km/h! I backed off and cruised at 40km/h for a bit, then the engine just silenced. My chain was dragging, and I was stuck pedaling. An autopsy revealed that my bottom bearing broke. So the Black Stallion is dead, awaiting rebirth, and I'm running my CH80 for the time being.
If you buy the Black Stallion kit from Gasbike.net, beware! This thing could kill! If I had the #41 chain I have now, it would not have snapped, my rear tire would have locked, and I would have gone over the handle bars at 40km/h. These engines are a blast, and very efficient, but in my opinion, they are unpredictable kit to kit. You get what you pay for, and right now, I'm trusting my $350 Chris Hill 69.9cc. He upgrades the bearings, as well as other things, to ensure a little more that there will be no engine malfunction.