w8ye

My Feedback: (16)

These mechanics go off to repair schools and someone at the school is telling them to destroy junk engines and not let the hobby fools modify them into something dangerous with no guards that is going to kill or maim someone and cause a liability problem for the OEM company.

Flathead

My Feedback: (11)

I aquired a "YARD MACHINE" (RYOBOI) engine the other day, and when I dismanted it, I discovered that it uses an O ring for the crankcase gasket. I have used O rings for sometime with great success. If anyone is interested in this arrangemnet I use, feel free to contact me: FLATHEAD

Flathead

My Feedback: (11)

This information should help those who would like a better Con-rod for your RYOBI. I have never had a a conrod failure, but I believe it is possible. For that reason, I have been looking. I aquired several POULAN 31cc weedwhips, and the conrod impressed me. It is solid steel, but the rod journal is larger than the RYOBI, but very similiar to the RYOBI. The wrist pin is the same diameter as the RYOBI. I pressed the journal out of the POULAN crank, and devised a mount for my lathe that allows me to fasten a DREMEL TOOL on the tool holder. I used an emery stone on the DREMEL to grind the journal down to fit the RYOBI crank. I then pressed the modified journal into the RYOBI crank, using SLEEVE LOCKER for further strength. Yesterday, I put the engine back togather and with everything else stock except for electronic ignition, a 18X6-10 wood prop, I recorded 6300 RPM. I ran the engine for 15 minutes. I will dismantel the engine for inspection before I run it again to see if there are any trouble spots. I will keep those interested informed as I futher modify the engine like larger carb, further timing ect. Sorry, but I have not figured out how to put pictures on this site, however, I have taken pictures. FLATHEAD

w8ye

My Feedback: (16)

Instead of using "FAST REPLY", use the "POST REPLY" and you will see the upload options at the bottom of the edit page.

The pictures must be in your compluter.

If your pictures are in a repository like PhotoBucket, you must right click the picture in photobucket to get its location and then use
[img]picture url[/img] in the RCU editor to make the pictures show up.

av8tor1977

My Feedback: (6)

Yeah, I'd like to see a pic of your Dremel mounted to the lathe as well.

AV8TOR

Flathead

My Feedback: (11)

I'm still technology challenged. Give me an e-mail address and I'll send it as an attachment to you and you can figure out how to get it on the forum. FLATHEAD

w8ye

My Feedback: (16)

Flathead sent some pictures

Flathead

My Feedback: (11)

Still hanging in there on improvments on the 33 RYOBI, and I continue to find differences. I dismantled several engines when I replaced the rod with a POULAN produced rod, see previcous post. I was compairing crankshafts, and noticed that one of the short-shaft crankshafts has a dfference as to where the keyway is. Using a degree wheel, it appears to me that there is a 10 to 15 degree difference. I looked at the long shafts engines (2) that I had handy, and could find no difference. It is possible I suppose that the crank slipped at some time since it is pressed on, or maybe it was an attempt by the manufacture to gain power or RPM. Any thoughts on this. I have always used electronic ignition on my "RYOBI" conversions, but it does seem possible that it would improve high end RPM, but may also be harderto start. Just wondering. FALATHEAD

fasteststang

My Feedback: (1)

Hey guys, I know this is an old thread, but I've read the whole thing and I'm superb excited to get going with my project. Thanks to everyone who has contributed, and laid down the ground work for those of us who wish to try to push the little Ryobi even farther.

83scamp

I've subscribed to this thread. I will be watching, as I have 4 of these little beauties at home that will be going on planes eventually. They are all virtually brand new(less than 1/2 hour each). One is going on a Dynaflite Super Decathalon, 2 are reserved for my Ziroli B-25(a someday project), and the last one.... ?? I made my own converstion kits for all of them. Two are short shaft, 2 long shaft.

Looking forward to more info on these motors!

LARRYKOP

Have been working on 31CC Ryobi's for the last year. Test flew a Bingo with a 31 yesterday. Flew great. Only 2 flights then it started raining. I have many pictures and video's of my conversion attempts. I'm not trying to sell anybody anything as I'm a retired machinist. I have run engines with the magneto and with the Electronic Ignition. Very little diffrence.
Send me a real E-Mail address if you want to chat because I have problems with this formum.
Thanks,
Larry Kopecky
1330 Hill Drive
Conyers, Ga 30094
[email protected]

APLANEGUY

Hello all,
I just finished reading through this entire discussion/topic and I have to say it's been very interesting and enlightening. You've confirmed many things that I discovered on my own and also opened my eyes to a few things I never even considered before. I've had converted Ryobis flying for several years now and I really love them. I've been able to get them to produce enough power that I feel very comfortable setting one up for my next project that I'll be starting in a few weeks (a 1.20 size Gee Bee R2 ARF). It should be a very good match for the 71" span racer. I have two otherprojects on the drawing board that will keep my shop filled for the next year or two (including my first giant scale twin) and they will also be powered by (you guessed it) converted Ryobi engines. I'm hooked on gas engines and conversions are my favorites. I just love tinkering with these little buggers.
This whole discussion has been very clear and helpful but I was hoping someone could clarify one thing.Something was mentioned a few pages back about modifying the back plate to reduce the volume in the crankcase. It was said that the mod allowed for an idle so slow and smooth that you could almost count the revolutionsof the prop (or somethinglike that). Attached pictures were mentioned but for whatever reason they can't be viewed any more. Maybe the files were deleted or moved or something. Whoknows? Does anyone know exactly what modificationwas made to the back plate? Are there any pictures that could be reposted maybe? I'd love to havemy engines idle nice and slow and smooth. They do pretty well with CDI ignition when they're set up right but still not supersmooth or super slow. Anyinfo to clarify just whatwas done wouldbe greatly appreciated.
I know this is a prettyold discussion but I'm gonna keep an eye on it anyway. Just can't seem to getmy fill of good information on these neat little engines...

Thank you all somuch,
Pete

w8ye

My Feedback: (16)

Those were linked pictures from Facebook I think? Apparently he changed his Facebook account?

But the technique of removing some metal from the back of the crankcase to place the back plate as close to the crankshaft as possible is a old trick used for many years.

On engines without the reed valve in the back plate some have added metal to the back plate to make it extend farther into the crankcase and therefore reducing crankcase volume.

LARRYKOP

Hi pete,
I have spent lots of time working on these 31's. I have auto-cad drawings of the backplate and reed valve mounting. I make the reed valve mounting plate out of 6061 aluminum. I mount the reed valve mounting plate to a really seroius 1/4" thick 'bow tie" shaped mount. I'm using a 3 7/8" X 2 3/8" bolt hole mount with 8/32 SHCS. I then use 4 1/2" Square 2" long standoffs. I had to make some fixtures to machine the reed valve plate. as you can tell the reed valve has a small preload on it so it closes air tight.
I currently have 2 flyable 31's. Both where tested on the Big Bingo. Sadly the Big Bingo bit the dust last wednesday. It got tangeled up in the saftey fence doing some touch and goes. I got 11 fifteen minute flights out of it. I ran both of my 31's in it and both of them never missed a beat. I'm currently building another low wing test bed.
Send me a real E-mail address if your intrested in pushing these motors to the MAX. I have a small machine shop with unlimited resourcees. I have lots of pictures if intrested. Not trying to sell anything. I'm retired and love working on these motors.
Larry
[email protected]

APLANEGUY

Larry,
I'll definitely keep that in mind for future projects. Right now my engines seem to give me all the performance I need and are very reliable. I'm setting one up for a 1.20 size Gee Bee R2 ARF I just bought and this will be the first 2 ring engine I've done. I can tell that you guys are 100% correct about the 2 ring advantage just by turning the engine over by hand before I started to work on it. All my engine cores except for one were single ring so that's what I've been using. Those engines all ran fine with sufficient power for my needs so far. The Gee Bee is gonna need a little more I think. With all the mods I normally do and the dual rings it should be just about perfect. If I ever get into a project where I really want to push the envelope hard I'll hit you up for an ultra high performance reed valve plate. Don't need it quite yet though...

Thanks,
Pete

LARRYKOP

Hi Pete,
I think you are getting me confused with somebody else. Everything that I have done so far with these 31's has been to improve reliability. I currently have 3 31's that are flyable. 2 of them have been in the air. The 3rd one hasn't flown yet but will be flown soon.
The 2 ring or single ring issue, as far as I can tell doesn't seem to matter. 1 of my motors is a single and the other has 2 rings. At the field one day I swapped motors and got nearly the same preformance. I used the same prop, 18X10 Dynathrust.
The 3rd motor, hasn't been flown yet. It has a single ring and it was a long shaft. I cut the crankshaft down, drilled centers in it and single point threaded a 5/16 -24 thread on it. I ran it thursday before the heatwave started and it started right up. On this long shaft 31 the keyway was not on center. It was off maybe 5 degrees. The motor seemed to idle slower and smoother. The top end didn't seem to be as high. I'm running all these motors on the stock magneto.
With the motor mount and reed valve issue. All my effort has been to get away from the molded reed valve mount and then to incorporate a better engine mount that spreads the torque out more evenly on the firewall. I use 3/8" 7 ply for my firewalls.
Larry

APLANEGUY

I was just saying I don't have a need to push my engines any more than they already are right now. I wasn't really questioning reliability.

I spun up the twin ring engine today for the first time (identical setup to the last single ring engine I put together). I have to say I'm impressed but not quite how I really expected to be. I found a little more top end (about 150rpm) but the idle was much improved over any of my single ring engines. A full 200 rpm slower (reliably) and much smoother sounding and then the transition back to "power on" resulted in less hesitation (not that there was very much before) and a stronger sounding "pull" up to full throttle. I'm gonna stick with dual rings from here on out. I'm a believer...

APLANEGUY

Larry,
You mentioned cutting down the long crank and threading it. Man, that would be so VERY handy if I could mod a couple brand new long shafts I have to use on a crazy twin project I'm gonna build this Winter. I really would prefer to have a shorter shaft so nothing has to hang out in front of the engine much either ahead of the prop or behind it. I may be able to hoogie-doogie something with spinners and leave the shaft out in front of the prop but I'd really rather not. You said you did "single point threading." Can threads be cut on these cranks by hand with a regular die or does it require a lathe or other fancy equipment to get it done? I guess I just always assumed crank materialwould be way too hard to thread by hand. Please let me know. Sounds like you have lots of knowledge in the machining department...

Thank you,
Pete

Flathead

My Feedback: (11)

Pete: If you are looking for shorter cranks, I would be willing to trade short for long, with or without bearings ect: Give me a shout at [email protected]

APLANEGUY

The problem is, for the project I have in mind, the short cranks are too short and the long are a bit too long. I may end up using a custom hub to get the length I want out of a short crank or maybe if I use just the right spinner I can conceal a long crank and keep it looking scale. I have to review my plans closer when I get the time. I was really just curious if the threading could be done by hand before I start cutting cranks and experimenting. I'll definitely keep your offer in mind though. Thank you...

w8ye

My Feedback: (16)

I was always able to run a threading die on the crank to run the threads back farther and then I was saw the crank off to the length I wanted.

av8tor1977

My Feedback: (6)

Yep...

AV8TOR

LARRYKOP

Hey Guys,
This is all about Ryobi #3. It is currently on my test stand and flyable. It came out of a 725R weedie. It was a long shaft version with a 1/8" keyway. It had a WA 526 Walbro carb on it. The long shaft extened 3 7/16" in front of the keyway. I cut it down and threaded it to 5/16 - 24 so it will interchange with my other 31's. On the test stand it had great top end but would not idle below 2,000 RPM. I swapped carbs with a WA 58. It now has the best top end and the best Idle of all 3 0f my 31's. Unfortunately this WA 58 needs to have the throttle arm flipped and then you need to make some type of throttle arm. The WA 58 has STIHL stamped in the metering cover. I don't know where I got it from. Sorry.
Larry

APLANEGUY

Thanks guys. When I get closer to working on that project I'll take a junk long crank (I have a couple in pretty rough shape) and run a die down it and see how it works out. Should make the whole project come together better if I can get the cranks just the length I want...

Pete

w8ye

My Feedback: (16)

The long shafts used to be 3/8-24