I converted a 31cc Ryobi for CDI ignition fitted a balanced prop and ran it on a test stand.
I was disappointed with the vibration at idle and at high rpm.
I also have a mag fitted ryobi and find this vibrates at idle but not to bad at higher rpm.
I rebalanced the flywheel of the mag fitted motor and the vibration was worse than before.
I have therefore concluded that the ryobi does rely on a out of balanced flywheel for dynamic balance.
What suprises me is that the converted motors with CDI ignition and no fly wheel to balance them must be out of balance .
Do the successful Ryobi motors use an out of balanced prop to smooth them out.
Has any one been able to convert a sweet running ryobi and what is the secret to balancing these motors.

I have a 28cc Ryobi with a flywheel I cut the fins off with a hacksaw. And balanced it with a prop balancer! Since then I have done 2 other engines! From the factory they all most perfectly balanced! I checked this off of another engine! My prop balancer is a frame work of yardsticks. With two aluminum plate’s ca to the top! And a Dubro prop balancer. The one you hold between your fingers. No heavy sides! Also check to make sure the prop is centered! And the prop hub is square to the flywheel! Check the prophub! make sure it’s not out of balance. And remember it’s a 2 stroke single cylinder it will idle rough this is my Ryobi conversion http://www.youtube.com/watch?v=6J7dG...e=channel_page If not you might have a bad bearing inside your engine. check it!

My brother has a Ryobi converted to electronic ignition on his big Ryan's Rebel. No abnormal/excessive vibes.

AV8TOR

I am running a 31cc Ryobi on a Homebuilt Airboat with no problems. slight Vibration at Idle not noticable at WOT cannot run long at WOT to fast for small canal and pond not enough room to turn around.

I converted several Ryobi engines. No extra balance was needed. They are sweet running engines. Your prop may still be out of balance.
Unbalance can be caused by:
1) mass balance long and short axis (mass vibration)
2) blade shape must be the same (blade pull difference causes vibration)
3) blade pitch angle must be the same (blade pull difference causes vibration)

Curiosity got the better of me and I stripped down a ryobi 32cc and weighed piston conrod etc and applied it to a formula 1/2 reciprocating weight + the rotating weight on the crankn pin.
It works out to 38gm which I hung on the crank pin and it balanced perfectly!
I will look at the prop etc now thanks for the comments and reasurance.

I found a lot of props from MA are grossly out of balance. Not on a horizontal axes but on a vertical axes. Like the one guy said there great engines!

Early on, there was post here about vibration with a RYOBI, and someone suggested to make sure the prop is installed on the TDC part of the revoultion. I have always tried to keep that in mind, and I have several RYOBI's that run really good. It may help you to locate the real problem if something else is out of balance. FLATHEAD 4

Just a thought I had a simular vibration that fought me on my converted ryobi. What I found was an osilation in the radial mount that I had made. It would only cause a vibration as you said at idle and would cross a vidration just above 3/4 throttle. A more rigid box tpye mount while not a "pretty" solved my problem. stay after it they are great little motors

Have a look at this post I just did: http://www.rcuniverse.com/forum/m_8313441/tm.htm

AV8TOR

I have my Ryobi running great now and working on a second one, I love it .
It is so reliable and now smooth running as well.
I think the motor was detonating on the coleman fuel as the compression has improved with time.
I am now using 95 octane petrol and a 20 x 10 master prop with plenty of weight in it to smooth the pulses out.
At peak rpm the vibration is minimal and with a electronic ignition it starts second flick once primed.
Opening up the thrttle from about half produces no further increase in power though so I think it it over proped but I don't need the power .
Thanks for the replys and help.
I have a 2 long shafts and 1 short but they all have the good reed valve!

Nice looking Volksplane. I was tempted to build one (full size) once upon a time. Stayed with Ultralight Planes and rented Cessnas, Grummans, Aero Commmanders instead. I did build some Vans RV airplanes, but they weren't for me.

AV8TOR