I have a Ryobi 31 cc installed and flying and I am very happy with the reliability power and economy of the engine.
I am not so happy with the vibration during high and low speed though and if I could figure out how to balance the motor I would convert another and build a 'Spirit of St Louis' with a Ryobi for power.
Does anyone know how to balance these engines as I know the flywheel is not balanced as per other weed wackers,but balanced with the crank as an assembly.
When I machined the flywheel I balanced it back to the out of balance of the stock flywheel,but the motor is not as smooth as it should be.
Are there any tricks to smoothing out the vibrations?

I'm not so sure that the engine is set up originally with an "out of balance" flywheel to help balance the engine, though I've heard this theory before.

I set up a CH Ignitions ignition system on my brother's Ryobi for his Ryan's Rebel, and it has very little vibration. Obviously, to do this I left off the flywheel....

AV8TOR

I tried to do a search with the RCU search feature. I know there is lots of data on here. To find it is another thing! I wonder if there is a page or "sticky" explaining how to use the search feature? Can some kind sole that knows his onions...post some good how to use the search feature. Maybe even start a thread...named BEST SEARCH OPTIONS. Thanks Capt,n[:-]

One simple test worth trying, and I know others will decry this, is to align the prop on TDC of the engine. My non-expert opinion is that if there is any imbalance brought about by the prop (even after balancing) it's probably best to have it on the same plane (non-aircraft) as the inherent imbalance that single cylinder engines have. One imbalance is better than two (one inherent to the engine and an introduced one from the prop).

From my own personal experience, including those of my friends, is that you'll get higher peak RPM keeping the prop aligned with TDC.

Others will disagree on either one or both aspects of my theory, suffice to say I've measured improvements on multiple engines and it's the results that count (even if the theory itself doesn't hold up).

Put the engine at TDC and ensure the prop is aligned vertically through the same plane as the piston/rod/crank throw. It costs nothing to try....

The other option is to just actually balance the engine. All you need is a gram scale and patience.

AV8TOR

One guy's take on balance for the Ryobi conversions.

http://www.geocities.com/CapeCanaver...1071/ryobi.htm

"...Check flywheel balance with a prop balancer or other suitable method..."