As Romore suggests, it may be the ignition coil magneto that isn't working properly. I remember a few years ago somebody had the same problem, and it turned out to be the ignition coil magneto, which worked fine for a few minutes until it heated up a bit and then quit, and then worked ok again after it cooled off. It's not a difficult job to change it. The air gap with the flywheel and magneto coil is the thickness of a business card, which is what I used when I reassembled the magneto for a repair job requiring removal of the flywheel and magneto on an HR215. The gap actually should be .016" + or - .008" on the HR215, which is probably the same on an HR214. I guess it's possible that the gap on your magneto is out of specs, thereby causing your problem. I just measured the thickness of a std. business card and it was .013", which gets you into the acceptable range.