Hi, I have a brand new EME35 that is suffering from vibration. Its only been run on the test stand so far, the carb is set about right (on the rich side) but it vibrates BAD.

Vibration at idle is ok, but up in the mid range its crazy, you can actuially see the prop hub moving arround. Smooths out some at max RPM but this might be just a change in frequency. Tried two different props both balanced andhub balanced.

I have noticed a bit of rotaional play at the prop, not sure if this is relevant.

Any suggestions gratfully received.

Just did some basic checks. The prop hub is running out by about 11 thousands of an inch.

The nut that holds the hub and centres the prop is concentric.

Is this eneough to cause the problem?

.011" is excessive in my opinion. I like to see .003" or less. This is measured on the face of the prop hub. Sounds like you may need a new hub.

I was surprised to read this thread. A friend has a EME 35 and it runs noticably smoother at all speeds than my 30 / 35 engines of another brand.

You know how we often buy stuff for upcoming builds and it often sits new in the box ...sometimes for months. I bought a EME 70 and when I finally got the build finished ..It sat for a while due to work then when I got around to flying it i discovered the crank was out 14 thou....by this time the warranty had run out...was told ..sorry can't help ya....so I say you better send it back right now.

I have a eye 35 with approximately 16 gallons run through it and still smooth. Are you in the USA and where was it purchased

The engine came from China, I can return under warranty but the postage is my cost.
Just ordered a new prop hub, will post results when it arrives.

If you're in the USA mile high rc sells them and has great customer service I have three from mile high

I am in France so still waiting for a prop hub.

I did pull the prop hub off and put it on a balancer, way out of balance as suspected.

I'm not sure the hub is a balanced piece, even for a good one. While it is for the most part symmetrical, there is a keyway cut in it along with a magnet that would affect balance and I've never seen any drillings or other machining that would indicate an attempt to balance. I would look for runout on the balancer just as if it were mounted on the engine.

The hub is not concentric, the deviation is 11 thousanths of an inch or so.

The balance is out a lot, and the keyway is not the lightest bit of the hub.

Also the hub is fairly solid and heavy (not machined away like a DLE) so i suspect that the hub is having a detremental effect.

I eventually got a new hub, unfortunately this didn't solve the problem.

During testing I noticed the vibration was at its worst arround 4000 rpm.

I then remounted the engine on the test stand upside down so I could adjust the carb whilst the engine was running. This made the vibration worse.

I also noticed the vibration hit at 4k on the rundown from flat out with the throttle shut. Also soot on the prop blades.

Lightbulb moment, the motor was mounted on a plywood upstand bolted to my bench, this formed a flat plane behind the prop causing the air to bounce back. A quick re-design of the test stand and all is smooth. Max rpm also jumped by 500 rpm.

It would appear test stand design does matter.

Just some info for you. Once your EME 35 is broken in it should spin the Falcon 20X8 wood prop to 6800rpm or the Falcon 20X8 carbon to 7200rpm. Also if you don't like the raspy and tinny sound of the stock mufler (I don't ) the stock DLE 30 mufler is a direct bolt on for the EME and it sounds much better.

It's a great engine, bolt it on something and go fly.

My EME 70 ran rough for the first couple tanks until the rings got seated.

I would take it up and do continuous loops (cycling the power basically) and see if that doesn't help it run a little better.