My glow one is pretty tight, but runs good, until it is cold outside. At about 10 deg. C or 50 F, it seizes right up. If you can get it to fire up then it is loose for a bit. I tried lapping it a little, but it seized quite easily and I twisted the rod. I got it straightened out, but the rod is quite soft. It must have a big difference in expansion rates with the piston and cylinder. It is quite a good running motor on a normal warmer day.