If you would like to stop your engine from having any movement on the tube as you power up, you can do the following:

1) Turn power unit on side with carburetor side up.  

2) Drill a 5/8 inch deep hole in collar where casing meets the tubing.  Use a drill bit that is slightly smaller than a #8-3/4 inch screw

3) Screw in a #8-3/4 inch screw

All done.