Hi all

I am a recent arrival to the fixed wing scene after flying helis for a few years. I purchased a polecat with a .40 OS engine and I have a vibration issue. It seems that there is a bit of movement in the crankshaft (i.e., you can move the crankshaft in and out slightly). Adding a washer does not seem to help as there is a lip on the crank which prevents the washer from actually tigthning up against the engine. Is this slack normal and could it cause virbation?

Thanks

A number of possibilities here
Is it an LA series motor? (OS - 40LA). They have plain bushings as bearings and some of them do have a bit of end float on the crank which is usually not a problem.
If it a ball bearing motor, the end float certainly shouldn't be there - change the bearings now before they self destruct any further.
The propellor or the spinner could also be out of balance.
Is it a new motor or a second hand one?

Hi there

Thanks for that. I'll check tonight what model it is. It is a second hand loan engine so no great drama. I didn't really want to have to pull the thing apart but if it is not an LA I may have to do that. By moving the crank in and out it does make a decent metal on metal sound so it may pay to do some surgery.

Cheers