is there any info available on hopping up the 31cc ryobi engine beyond electronic ignition ?
like porting, port timming raising compresison etc?
i can find this info for the hommie 25 &30cc why not ryobi ?
thanks fj5

Have you looked closely at the rod and crank in a Ryobi??? Factory redline is 7500 rpm

no i havent disasembled it yet , are they that bad?

maybe i should go with a homelite30cc ?what do the 30cc engines gcome in when new?
thanks fj5

You can get the 31cc Ryobi just cheaper than about any engine. There is so may used in gas powered blowers..ect. They are everywhere!!! People throw away or give away lot of the small engines like this because it cost to much for repair work. Cheaper to buy new. Get one and hop it up....nothing to lose...just some of your own time. Go for it. Good luck Capt,n

The Ryobi has a two piece stamped steel connecting rod held together with two rivets.

In looking for a 30cc Homelite, I just ordered a new shortblock from the dealer for $65 at the time.

ok $65.00nice price.what dealer someone local to you or from homelite?good info ,still gotta go with the ryobi parts r paid for
ch ignition is on the way but $65.00 hard to beat! any one have contact info on frank bowman for ring
thanks fj5

The Homelight 30 I bought was from a local dealer.

Someone on here about 6 mos ago had the UT # of the new short block and he found one pretty cheap

Actually people are taking the 33cc Poulan and Homelite chainsaws to make their conversions. They find them on sale for less than $100 and go at it. The older black top Homelites are easier to convert than the new red top ones.

Enjoy,

Jim

thanks

thanks but cant aford the weight my ryobi will have ch ignition to save weight how much modifing can i get away with if any\.
i am going to go wiyh a bowman ring is yhere anything else i can do to improve perforemance that wont stress the rod or crank?i dont want to blow it up i hate to change horses mid streem but maybe i should go with a homelite 30cc ? i hate to because of the weight.
thanks fj5

I have looked at the Ryobi crank and rod and to many it may appear fragile. To my knowledge no engines have been reported blown. I have also turned the Ryobi 11,000 RPM briefly. From an engineering perspective it is believed the crank assembly will withstand as much abuse as an aluminum rod.

I would not hesitate to tune the engine to the max. If she blows she blows. If you tune engines you are going to break them.

Bill

I wouldn't be afraid to Hi tune the Ryobi engine, This engine is a tough little gem, inexpensive and easy to convert
I fly mine with a glow plug conversion (save on the electronic ignition) and run it with gasoline/glow fuel mixture see "gas fuel with glow plug no ignition" thread here on the engine conversion forum you will find a lot info. I am turning an APC 18x6W prop at 8100-8200 rpms with this mixture.

Thanks the thread was very interesting.

I have an operational weed eater and an engine that I am converting. I tacked the operational weed eater with an electronic tack at 8100/8200 RPM. I have assumed that 8200 RPM was the design speed.

I will try the gas/glow concept.

Bill

ok going to do it! ill start small though, bowman ring electronic ignition with advance (i know i dont need it but i want the experience with it for larger conversions)
now can i eliminate the gasket between jug & piston to increase compresion? my piston hits counter weight without the gasket it just scrapes a little.is this normal? can i remove material from piston skirt for clearence?(yes i have it in corectly)
i was also contemplating stuffing it? i have read this will this help increase performance
how about a larger carb? any suggestions on a size?
can i open up exaust port? do i need to blue print it first? what is a good duration for the ryobi ? icant find this info anywhere
any help is appreciated
fj5

This is the easiest way to get a big boost in horsepower. The $62 tuned pipe for the Evolution 26 from Horizon. Homemade header, ran it for the first time this afternoon. Didn't get any tach readings, the setscrews that hold my header together kept coming loose (I'll have to get the header welded) I did get the carb adjusted well enough to see that this is a combo worth pursuing. Run it about a minute, adjust carb, then I'd have to tighten the setscrews in the header. MACS used to make headers for the Ryobi, but I haven't seen them listed recently. This thing was turning the MA 18x8 WAY faster than it's ever ran before.

another isue i have with my 31cc ryobi conversion is the spark plug .factory isa dj8j i know i need a resister plug would it be a rdj8j? thats what i have been looking for and not finding, am i looking for the wrong plug? if so, what is the corect plug? any heip is appreciated
thanks fj5

flip flop let me know the numbers after you tach it .how much was it? looks cool
fj5

I would also be interested in the prop numbers. Incidentally my calculations indicate that a 16-8 prop represents about 5% greater load than an 18-6 prop.

A ST 90 muffler to engine piece will almost fit. People throw those away.


Bill

RDJ*J is what you want

Flyjoe, no you can't eliminate the gasket between the jug and the case. Not only does it seal the jug to the case, but by removing it, you chance the timing on the engine... The exhaust and intake ports will open later and close sooner, like if you retarded the cam timing on a four stroke. This is fine for low end, but we all know you're not after that. Go by Two Stroke Performance Tuning by A. Graham Bell published by Haynes. It's probably the definitive book on, uh... two stroke performance tuning. It tells you how to do the math to build a proper tuned pipe and header combo, how to port, where to port, when to port, how to modify the quench area of the combustion chamber, fuels, oils, carbs, and way more stuff than you'll ever need. I've been reading the book for about five years, and basically, there is no set "do this and this to get this" with a two stroke. Every engine is different from another, and the port timing and tuned length is going to be different every time. It's a black art, basically, and you need to experiment to find the right setup that works for you. Plan on buying a few cylinders and modifying them slightly different to each other and trying them all out to see what works best. Same with the pipes. I can tell you that you're on the right track with stuffing, but make sure you rebalance the crank. Pay VERY close attention to the ports and pipe, and you should make some good power. With this book, I was able to get 54 WHP out of a Honda CR125 in a '99 CRG shifter kart chassis.

terbough bob
thanks ill look for the book .

You can remove the cylinder base gasket and use crankcase sealer to replace it. Permatex makes a product for sealing crankcase halves on motorcycle engines. I have had no problem with this method. As for returning the port timing, you can file the piston at a 45 degree angle, at the port location. Just stay above the top ring groove. Make this cut equal to the amount that you lowerd the cylinder. When hopping up Cr125 Honda shiftkart engines we used this method to test port window openings. Pistons are cheaper than cylinders. When we got to where we wanted we would then make the cut in the cylinder and use a piston that was not cut. The engine wont know the differance and for a one off it should be fine. On a piston port engine, the bottom of the piston on the intake side can be cut to restore intake timing also. As you increase compression you may have to use super unleaded fuel. I for, one, have never been able to break a Ryobi 31. The book mentioned earlier is the best one out there for understanding two stoke theory.
Good luck and let us here how you came out. motorhd

motorhd
thanks for responding .i do intend to get the book on two stroke tuning, to give me a better understanding of what im looking for . but getting back to what you were saying ,if my base gasket is.020"thick and i remove it ,in order to restore the intake and exhaust timing i would need to cut .020"from the top of the piston at the exhaust port location on a 45degree angle,
and cut .020"from the piston skirt at the intake port location (or at the transfer port location on a reed valve engine ) to restore intake and exhaust timing to stock setting? and all of this piston cutting is just to try out the comppresion increase
and intake\exhaust timing changes ? hopefuly i am corect in understanding this much.