[FONT=Arial, Helvetica]Question:[/FONT]
My front end wobbles when I put the prop on. Is the shaft bent?
[FONT=Arial, Helvetica]Answer:[/FONT]
In most cases, Jett crankshafts do not bend. They are more likely to break underneath the front bearing during a crash (very rare), than to bend.
What usually happens is that the front removable stud bends. This is what it is designed to do. The stud should always be replaced after a crash or runaway (sheared propeller), and should be replaced as a maintenance item every year or so.
If the front of your engine wobbles after you tighten the propeller, then there are several things to look for. First and foremost, remove the stud, clean the threads in the shaft and replace the stud. Screw the stud all the way in, then back it off slightly so that it rotates freely. If you screw it in tight, then it cocks slightly as it tightens. Second, remove the prop drive and lock cone. Clean them carefully, replace and fit the front end with a new propeller. Tighten the spinner nut and inspect. Unless there is a problem with the fitted parts, it should be aligned. During a crash, it is also possible to damage the cone and prop drive. They may need to be replaced.
If the stud still has run out after being cleaned, and fits tight in the shaft housing, then this is the most likely problem. The crank may need to be replaced (very rare). The stud should be loose enough to self align as the prop is tightened. You should return the engine to Jett for inspection.
