I just recived an old PT-60 from a friend at my field. Not long after I ordered this engine, http://www2.towerhobbies.com/cgi-bin...&I=LXFV79&P=ML and this prop, http://www2.towerhobbies.com/cgi-bin...&I=LXZ979&P=ML. I noticed after I ordered this prop that it is ment for 4 strokes. After getting everything installed I started up the engine and noticed an unusual amount of vibrations. Could this be caused by the wrong prop or an unbalanced prop? Any help will be greatly appreciated.

I don't think the size or shape or "type" should be a problem as long as it fits properly on the crankshaft and is properly balanced. Also don't try to idle too slowly. A lot of mass swinging out there. It is on the upper end of the size limits and you might want to try a slightly smaller prop either in diameter or pitch, at least during break-in.

A lot of engine for a PT-60 IMO.

No matter what the vendors say, props may not be balanced. Probably a combination of a low idle and an inbalanced prop can be the culprit in your case. Go ahead and check the prop balance and see if that helps with the vibration.

DS.

The main problem is that it has horrible vibration throughout the entire rpm range.

As you can tell, I'm fairly new to rc flight. I have some expierence with electirc flight, but this is my first glow burning plane.

I don't have any LHS's within 100 miles of me and I don't own a prop balancer. Is their any way to balance a prop just using "around the house" stuff?


Also, I fly at over 7000ft. that's the reason for the big engine. (but who doesn't like a little extra juce anyways)


Thanks again for your help and advice

You could put a simple balancer like this together for a few cents. A chunk of balsa or two by four, acouple of single edge razor blades and piece of welding rod with some masking tape to size it up to propshaft size.

If you using a cheap plastic spinner I would suggest loosing it, Instead use an aluminum spinner nut, These look better on a trainer anyway far better.

Since I'm fresh out of my household welding rod, I think I'll use a dowel--with your design! Thanks!

Also new engines will not run as smooth as broken in engines. This is because the cylinder wall and ring friction is trying to grab the piston near TDC and on ringed engine at BDC as well. They will run smoother when broken in.