I actually just had a bad engine, when I got it and looked it over it looked good, when I went to put the cylinder on it wouldn't go on without a struggle, felt like the studs were bent but when I checked them they were straight. Once together and on the bike I got it running and the vibration was so bad I couldn't get over 15MPH. I believe the engine case half's were not matching (just off a tad) and the crank was not aligned properly causing the vibration issue. I also use Bicycle-Engines and called them and Molly helped me out. I had to send the motor back for there inspection and within a week had another engine on the way. Best part is I purchased the engine back in May and was working on the build and I was just about at the 6 month period and true to there word the covered it no problems.