manks7477

I am about to buy a Ryobi 31cc Gas conversion engine. I understand that this is a very good motor, does anyone have any strong feelings about the engine? I am buying it to power a 1/4 scale Chipmunk (about 18 - 20 pounds) and 91" Span.

I would love to hear your thoughts.

manks

soarrich

My Feedback: (98)

I've converted 3 Ryobis so far, they are a good cheap motor. I get 7400 rpm with my oldest, and 7100 with the two new ones using a Master Airscrew 16x10. I bought some for $49.95 'reconditioned' from Harbor Freight, they're new, someone just returned them, two I got for $12.50 on eBay, they where used power heads off weedwackers which is probably a good thing, no break-in. You might go to a local lawn/garden repair shop and see if you can get a junked one with a good motor.

If you use the mag you either have to use a rope or a starter to start them. I now convert them to IE ( http://lsproengines.com/lspro_012.htm ) now they hand flip easily. To get the most out of them you should be able to adjust the timing, they need more advance than they are set up with.

I made mounts out of 2x3 aluminum. There are at least two types, one looks like a model airplane engine, the other has the cooling shroud molded on, ok for raidail engine cowls but not for a Chipmunk. The Chipmunk you would want IE so you don't have that big mag flywheel on the front.

soarrich

My Feedback: (98)

Oh I forgot to say mine powered a 88 inch wing span 16 pound plane marginally OK for scale like flight but not a lot of power in reserve. You might want to look into this engine, my friend imports them, they are better than the SPE26. I'm flying two planes now with them, a Celmark S2 pitts, and a 67 inch Yak54, really a nice engine.

The picture below is after I coverted the plane to a differnt engine.

pe reivers

I worked on riobi engenes for a while and had a ball with them.
See http://home.wanadoo.nl/pereivers/ryobimods.htm for tuning.
The mag ignition versions are a bit hard to start by hand, but will take an E-starter very well.
The late Mag ignitions are limited to 7000 rpm. Read the patent pending number on the flywheel, and read the data in USPTO.gov patent literature.
Do not tamper with compression ratio, because the conrod is a steel stamping, and not a wrought steel unit. Crankcase bearings can be improved.
Not all cylinders are very suited for our use. Some have compression reducing slits inside the bore that very much reduce idle stability and spool-up. Keep idle at all times above 1800 rpm, or the engine may cut out suddenly.

soarrich

My Feedback: (98)

So that's what they're for. I thought they might be to take the bark out of the exhaust, they are very quite.

mikenlapaz

Find another engine. Take a look at some of the chainsaw 45cc or larger if you want to convert an engine to RC flight for a 18-20# plane.

Ralphbf

My Feedback: (27)

He's right there are much better engines out there.

A worked over Toro 25cc is lighter and more powerful than a 31cc Ryobi.

Echo blowers are cheap and powerful. I just bought 3 40cc blower motors off _bay for $25.00
for the lot. Perhaps I can get one good one out of the lot.

pe reivers

indeed: that, and to lower compression ratio for easier starting. But they also spoil the exhaust power pulse if you want to run a tuned pipe.

manks

I purchased the motor already converted. From what I understand it is flight ready, and spins a 18X6 Prop at 7200 RPM - not sure how good this is or not, I am assuming it is pretty good. The fly wheel has been machined,

Here is a link to a picture:
http://www.rccanada.ca/bb/download.php?id=32061

and another
http://www.rccanada.ca/bb/download.php?id=32206

I paid a total of $112 CDN shipped for the motor, so it is not a big risk. Please let me know what you guys think.

Cheers!

manks

av8tor1977

My Feedback: (6)

Sorry for the bad news.... Well, the good news first, is that it would probably fly the plane, somewhat. The bad news is that you're not going to like the performance at all. You really need at least a good 45cc engine for that plane.

AV8TOR

soarrich

My Feedback: (98)

You have a engine that will serve you well, from what I've seen they just run better with age, the motor is worth what you paid for it converted. I think you're asking a bit much for it to fly a 91 inch Chipmunk. If the Chipmunk has a good airfoil like a Clark Y it my fly it in a scale fashion, but with a symmetrical airfoil I doubt if it will take off.

manks

The plane is designed for a 1.04 - 1.20 sized glow engine. I have seen a review that used the Ryobi 31cc engine and it reported that the plane flew very well with it. Others that I have read have used a G-23 or G-26 engine, so I am comfortable the I should have enough power. The previous owner of the engine said it flew his 18 lb 88" plane (NOT SURE OF TYPE). I guess we will see how it all comes together.

According to the previous owner, the engine spins a 18X6 prop at 7200 RMP - not sure how good that is, but I think it will be enough.

What I am looking for is scale flight with a bit of extra power, I thought a 31 cc motor would be enough for that.

av8tor1977

My Feedback: (6)

A G-26 has considerably more power than a Ryobi, but go ahead and see how it goes. I think you will want more power.

AV8TOR