I am considering a Ryobi 32 conversion for a 4*120. I know the weedie conversions are a bit heavy and not a great power to weight ratio, but is this a "Real dog" that should only be used on a large Cub or similar plane, or would it give the 4*120 the same performance that say a 120 glow 4 stroke would? I am not necessarily looking for unlimited vertical, but have already had an underpowered trainer and prefer to have some reserve power on any planes I build from now on. I've already got one fellas input who flys a Ryobi/ 4* 120, but would also like a few other opinions if possible. I really like the 4*120 and plan to build one this winter, but engine cost will definetly have a bearing on whether I do or not.

Thanks guys,
Dwight Hayden

I have a Ryobi 31cc in a 4/120 and it certainly is no dog.I can jump the plane off the field in 10ft if I want to and then go vertical for a hundred feet if I wish.My set up uses a CH ignition and so is at least 10oz lighter than a flywheel setup even allowing for a black box,switch,and 1400mah.My engine will turn a 16x8 at about 7600,but its well broken in and uses a higher quality repalcement ring that ups the c.r.
No I dont think it will match a hotter 120 4 stroke,but it cost me something like half the price and uses 87 octane at maybe 10% of the price of glow fuel.It needs much less fuel on board at takeoff,and so can utilize a smaller tank too.......I stuck three servos in the tail for the elevators and rudder and not only did I not need extra weight to locate the cg,but actually ended up slightly tail heavy.

Thanks Kevin, Where did you get the better sealing ring? And did you also trim the base of the jug or use a thinner gasket to increase compression? Whick conversion kit are you using, as well as muffler?

I appreciate your input.

Dwight

(Looks like I'll have to get another weedeater next spring, mine may be airborne

PISTON RINGS FOR RYOBI 31
Try contacting Frank Bowman. He manufactures repro and current piston rings for our modeling needs. He can make standard and Dykes type rings. If he doesn't have the ring you need in stock, you send the piston and cylinder and he will make it then. prices are $7.50 up to $9.50. His work is of the finest quality.

Frank can be reached at [email protected] or 1-505-327-0696 ( 6pm to 9pm mst. weekdays) and the following address:
Frank Bowman
1211 N. Allen
Farmington, NM. 87401

I,m using a Bowman ring and this gent and his products are a class act.It alone increases the compression of the engine somewhat since it overlaps the pin in the piston and seals the joint insread of just butting as the stock ring does.
Im using a B&B mount,a Bisson muffler,and the prop driver comes with the CH ignition.
Utilizing a used or heavy discount weeder,and allowing about $120 for the CH conversion you should be able to bring the cost of the engine in about $200.It isnt worth putting much more into this type of conversion when you consider an RCS 1.4 sells for $325.
Actually I only went as far as I did to prove to myself that a weeder conversion was viable for most 1.20 sized models and I assumed I could sell the CH unit used or use it on other engines.To really keep the costs down a shaved flywheel is the way to go and this will fly your 4/120 with some spirit but its a tight fit,weighs a lot more and is ugly as sin if you dont cowl it,which presents its own problems ,but is possible.There is no free lunch!
If I can get my new digicam working,Ill post a picture here of my installation in the next few days if that will help.
IF you havent already done so ,check out the weeder conversion part of WWW.rcfaq.com/home.htm
There is a Ryobi4/120 article buried there,on Marty Mammersmith,s home page.

Kevin, how did you mill down the piston ring pin (partially, of course) to fit the Bowman ring over it? I used a Dremel tool free-handed but it was very dicey. I'd recently bought a Dremel tool drill press stand, so I might be able to rig it up some way to act as a poor man's milling machine.

BTW, you're absolutely right about Frank's work being of first class quality. Well worth the money.

I used a diamond chip drum in a moto tool.......I didnt worry too much since the pins only function is to prevent the ring from rotating and fine machining didnt seem necessary ....fits and runs OK post surgery and the CR is definitley higher.......Apparentley any newer 31 cc now has two rings with a better seal and compression as a result as it comes from the factory,and I dont know if the Bowman ring fits or not,although Im sure he will make them for anyone that wants to buy two and try.

I just used a small ball peen hammer and tapped the pin in a little farther with the edge of a corny dog stick. Took about 30 seconds!

Yeah....and if you had ball peened it a little too hard,or the corn dog stick slipped,the pin would have been buried and you would be digging for it or ordering a new piston......

i would just take the pin out and ad to the weight saveings

To anyone thats interested I have a Ryobi I was going to do a conversion on I will sell. I bought the weedeater and broke the engine in and took it apart, now it is in a box and will probably stay there forever.

$25+ 3 shipping if anyone wants it.

Thanks

rpmodeltech is it a long shaft or short shaft?
fossil

Do you still have the Ryobi for sale? What size motor is it?
I"m definately interested.
Thanks