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RYOBI 31cc flywheel question - 11/28/2012 10:41 PM   
jp1961


 

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From: metamora, MI, USA
Status: offline 		I'm converting a 31cc Ryobi engine. When I had the flywheel off, I checked it's
balance on a Du-Bro prop balancer. Wow, it's not even CLOSE to be in balance.
Is this flywheel counterbalnced for some reason? There is a warning cast on the
flywheel to NOT modify it in any way.

Jeff

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RE: RYOBI 31cc flywheel question - 11/28/2012 11:11 PM   
pe reivers



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Status: online 		The Ryobi has a laminated stamped steel crank web that needs additional balance mass in the flywheel.


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RE: RYOBI 31cc flywheel question - 11/28/2012 11:19 PM   
w8ye



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Status: offline 		The balance question is often said about the flywheel but the out of balance is not in the direction it would need to be to balance the engine.

I balanced mine and the engine runs as smooth as my other gas engines.

The phelan brand flywheels are the ones that are out of balance.

I used the High Point prop balancer but the Dubro one would work also.

I did the cutting with a small air powered die grinder with  a A11 burr.


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RE: RYOBI 31cc flywheel question - 11/29/2012 11:59 AM   
pe reivers



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Status: online 		In the Ryobi I modified I kept the flywheel at original balance when removing the fins. No extra vibration was noticed, so I guess it's not that big an issue in this engine.


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RE: RYOBI 31cc flywheel question - 11/29/2012 12:52 PM  1 votes
tkg


 

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Status: offline 		When converted to a CDI ignition the flywheel is removed and a 0 balanced prop hub is used. No vibration problems.
To check things out you would need several Ryobi flywheels and compare the out of balance and where it is.

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RE: RYOBI 31cc flywheel question - 11/29/2012 1:31 PM  1 votes
pe reivers



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Status: online 		Or do a dynamic engine out of balance (amount and position) on the assembled engine.
Because a single cylinder engine cannot be balanced completely, every engine has a certain range of possible balance weights, which will all be a compromise at best.


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RE: RYOBI 31cc flywheel question - 11/29/2012 3:45 PM   
w8ye



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Status: offline 		At the time of converting my Ryobi, I noticed that there were no drilled holes in the Phelan flywheel. It was just  "As Cast".

I did a couple Homelites that had Walbro flywheels and they were much closer to being balanced.


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RE: RYOBI 31cc flywheel question - 11/29/2012 5:05 PM  1 votes
av8tor1977



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Status: offline 		I have run into this before. I converted a Ryobi to CDI ignition and removed the flywheel magneto. That engine shook like a concrete vibrator!! In that particular Ryobi, the flywheel was not zero balanced. The flywheel helped balance the engine. I took that engine apart and built another one with a different crankcase and crank, and it runs very smooth with no flywheel. Upon close inspection, there was a very noticeable difference in the crankshaft bob weights, and the crankcases had a different inside diameter where the crank turns.

So, some Ryobis, I think it is the rather old ones, need the flywheel to balance the engine. I have played with a lot of Ryobis and only encountered one that was flywheel balanced, so I think they are fairly rare....

AV8TOR

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RE: RYOBI 31cc flywheel question - 11/29/2012 5:10 PM   
av8tor1977



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Status: offline 		I found where I had posted about this problem before. Here is more info: www.rcuniverse.com/forum/m_8313441/tm.htm

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RE: RYOBI 31cc flywheel question - 11/29/2012 5:59 PM   
pe reivers



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Status: online 		Too many Ryobi versions. Still they are nice engines if you get the right ones.


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RE: RYOBI 31cc flywheel question - 11/29/2012 10:50 PM   
av8tor1977



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Status: offline 		Yeah, I've had fun with them, and they are cool for airplanes with narrow cowls like Mustangs, Tiger Moths, etc. I have one in a 76" span Tiger Moth biplane that flies great, and nothing sticks outside the cowl.

The later model Ryobis went to a one piece crankcase design that is not as easy to convert, and then even later than that, most of the Ryobi machines I have seen have Homelite 30cc engines in them. The Homelites make good engines, but are more work to convert and have a side mounted carb and exhaust unlike the earlier Ryobis.

AV8TOR

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RE: RYOBI 31cc flywheel question - 11/30/2012 10:51 AM   
pe reivers



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Status: online 		Nice work!


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RE: RYOBI 31cc flywheel question - 11/30/2012 5:27 PM  1 votes
av8tor1977



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Status: offline 		Thanks! I just did all my usual hop ups to this Ryobi; 150 degree exhaust timing, tightened up the deck clearance, 11 mm carb and free breathing muffler. But it runs exceptionally well. It turns that 18 x 6 Top Flite at 8500 rpms! For now I don't run it at full throttle because it would blow up. Need to put a 20 x 6 prop on it probably. One of these days....

With all that wing area and the Ryobi, it is airborne the second you give it the throttle!

AV8TOR

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RE: RYOBI 31cc flywheel question - 11/30/2012 9:37 PM   
Flathead


 

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Status: offline 		Just wondering, what explodes first in the RYOBI at or above 8500? FLATHEAD

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RE: RYOBI 31cc flywheel question - 11/30/2012 10:04 PM   
gr8flyer55


 

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Status: offline 		Just run one at that speed and when it suddenly stops, take it apart(if there is anything left !!) and take pictures!
I love a good laugh!
I have one that left its mark that I can post pictures of. Rod mangled and twisted, damaged case, ruined piston and cylinder. Should I continue??
Mine was turning in excess of 8 grand when the prop flew off after it stopped. So, another case of which came first, the chicken or the egg?

John


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RE: RYOBI 31cc flywheel question - 12/1/2012 1:49 AM   
Flathead


 

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Status: offline 		I was just wondering, because I have three with the "ROD MODIFICATION" that I have posted using a POULAN rod and 8500 to 8600 was doing good. I have propped them for around 8000 or around there, but on some of the flying I do, I know that they wrap up on the down slope or in a spin. Maybe I should back off a little more. I have plenty of power. Thanks. FLATHEAD

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RE: RYOBI 31cc flywheel question - 12/1/2012 2:36 AM   
gr8flyer55


 

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Status: offline 		Is there a link to that rod change somewhere? I'd like to read up on that. I have at last count, 12 Ryobi style engines in various forms but none using the stock magneto, they are all CDI. I will post a pic of a side carb reed induction with side exhaust I converted. This was used on an ACE 4-120 Ultimate Bipe-RCM conversion that had a bad landing or I'd still be flying the wings off of it.
Anyway, I love this engine and want to read what you have done with the rod to add strength to the weak point of the Ryobi engines.
I also was reading something about someone on here that was going to make a machined aluminum rod but haven't heard anything since about it.

John


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RE: RYOBI 31cc flywheel question - 12/1/2012 5:28 AM  1 votes
av8tor1977



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Status: offline 		The rod is the weak link, and it is commonly accepted that it is good to about 7500 rpms static. The stock rod is stamped steel, and quite weak. I'm actually rather surprised it holds up to 7500 static myself.... With a good rod, the rpms would be limited by the crank, and I don't see that as being a factor below 10,000?

That just might have been me that talked about machining up an aluminum rod for the Ryobi, as I have thought of doing it many times, but still haven't gotten around to it.

AV8TOR

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RE: RYOBI 31cc flywheel question - 12/1/2012 6:07 AM   
1QwkSport2.5r



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Status: offline 		Are the homelite 30cc rods the same type of construction or do they actually put a good rod in them? I have not pulled mine apart yet. (I know it's not a Ryobi, but I'm looking to prop my Homey to turn up to 9000-9500rpm.)

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RE: RYOBI 31cc flywheel question - 12/1/2012 7:00 AM  1 votes
gr8flyer55


 

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Status: offline 		Actually I think it was you that mentioned the aluminum rod. I myself would be very interested in one when and if you start doing them. I looked at a lot of my engines this evening and all but the Ryobi's have cast aluminum rods. Lower is needle bearing, upper on most was bronze bearing. I would be happy if I could find one that was just a swap fit. Probably be better off just making one since the lengths are not going to be interchangeable. I actually made one on e for an old OS-20 and it is still in it with well over 100 hours on it by now on a Dumas Swamp Buggy with pusher prop. Maybe I was a lot more energetic as a machinist back then. Takes me forever to just make one piston ring now. I'm more into electronics at present with our CDI project taking up a lot of my time now.
My one Ryobi with side case reed induction is a real rare engine. Came out of a Ryan leaf blower, and I believe it is around a 26cc cause the piston is much smaller than a 31CC Ryobi. Side exhaust also making it a very compact length engine. It needs a Bowman ring though cause the end gap is over .025 and leaky compression. I'd love to do some mods to it but don't want to ruin it either.
Just got a Kawasaki 22CC a few months back that also looks promising. Main interest now is doing a short shaft Ryobi. The long shaft crank I noticed has two drilled holes in the counterweight for balance, whereas the short shaft versions do not. Big difference in vibration levels without a flywheel !! CDI on both, both start by hand in two flips, but that's where the similarities end.

John


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RE: RYOBI 31cc flywheel question - 12/1/2012 11:34 PM   
av8tor1977



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Status: offline 		The Homelites are good for 10,000 plus rpms. I have one that turns 9400 static rpms; probably well over 10,000 in flight. The boat guys buzz the hell out of them too.

AV8TOR

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RE: RYOBI 31cc flywheel question - 12/2/2012 2:22 AM   
Nosedragger


 

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Status: offline 		12-13k is all they are good for in a boat.after that they blow up.

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RE: RYOBI 31cc flywheel question - 12/2/2012 3:07 AM   
Flathead


 

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Status: offline 		For those interested in a better con-rod for the "RYOBI", go to "ANOTHER DARN RYOBI CONVERSION" page 25 and there are instructions and pictures. You need a lathe to trim down the bottom "CON ROD" to fit the RYOBI crank. The conrod is out of a "30" cc (I think). If you need additional info, let me know. FLATHEAD

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RE: RYOBI 31cc flywheel question - 12/2/2012 3:29 AM   
w8ye



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Status: offline 		http://www.rcuniverse.com/forum/m_8479610/mpage_25/key_/tm.htm


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RE: RYOBI 31cc flywheel question - 12/3/2012 2:50 AM   
captinjohn


 

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Status: offline 		AV8TOR, if you can find a full size airplane prop...the metal is very good for making rods. This is what Burt Monroe did when he modified a Indian Motorcycle engine too set a World fastest speed record.  Be sure to watch the movie and the added clips at end of movie.   Capt,n

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