Need Suggestions, I bought an OS LA 40 used, The engine is very reliable and runs well. I mounted it in a GP PT-40 that I just finished. During taxi testing, I found that the engine makes a metallic noise as it is running as well as creating a moderate amount of vibration. I have checked: the crankshaft with a dial indicator which is true, engine and mount are secure, propeller was balanced. After a fuel tank run the cylinder head temp was checked at 180 degrees. Do these bushing motors make a lot of noise? Any help would be appreciated
Tom

Bushing Engines like the LA and FP series have alot of end play in the crankshaft and the crankcase. Lots of thrust play also you will hear the crank ping off the backplate. That is probably the metallic sound you are hearing. How was the propeller balanced, if you balance a propeller correctly you can place the prop in any position and it should not move? If the prop still rotates when placed out of the horizontal and it rotates back down, then you will have to balance the prop hub.

will

Thanks, I patiently balanced the prop with a TF magnetic balancer both laterally and longitudinally. It is balanced so it can be positioned at any point without movement, took about an hour. It is a Master Airscrew 10x6 and was disgustingly out of balance right out of the box. I did not balance the spinner, however, as it runs true using a dial indicator.

AP:

Try it without the spinner. If it's a Tru-Turn it is probably balanced, but the Spin-Right, Vortec, all the other metal spinners, I've not found any that were balanced out of the box, if they showed run-out with a dial gauge I didn't even try to balance, the run-out just meant they were faulty. Trash time, or send it back.

Bill.

Thanks. Bill I will try it without a spinner and see how it goes.
-Tom

I,ve had several of the LA 40 and 46's. The black plastic Master Airscrew props do make alot of noise on this engine for some reason, try a Wood Master Airscrew or an APC. Also, another rattle noise comes from the crank endplay. I have had good success with making paper shims or washers and installing them between the drive hub and the motor. Install the shim and tighten the prop then check the play, if it drags make a thinner shim, if it is still loose add a shim, Add shims till there is no play and it turns free. The paper shim(s) have lasted me over 70 flights and really quiets the motor.