What kind of rpm numbers are you guys getting, and with what props with your Ryobi 31cc engines?? I know they are not powerhouses by any means, but mine seems to be really doggy. It's not really broken in yet with only two tanks of fuel and a new Bowman ring, but it's only turning a Top Flite Power Point 18 x 6 at 7000. I raised the exhaust port timing to 150 degrees, installed an 11mm carb, open muffler, installed a new Bowman ring, etc. and I really expected a little more out of it. It is the single ring piston and cylinder with no slots. What performance are you guys getting??

Thanks,
AV8TOR

7160 rpm on apc 18-8,stock two ring engine,no mods.40 to 1 gas oil mix.


Waldo

Sure beats mine. I guess I'll run it a while and see if it breaks in and picks up. If not I'll pull it apart and see if something's unhappy. Shouldn't be, as I went through the whole engine when I set it up. My little unmodified Echo/Kioritz 23.6cc turns a slightly larger prop over 7500!! I wanted the Ryobi for this project however, as it is a Tiger Moth biplane and the Ryobi fits completely under the cowl with no ugly holes for mufflers, carbs, etc.

Wish me luck!
AV8TOR

av8tor,
You are at over 5,000 feet and Waldo is at sea level. An APC always turns faster then a TF prop. Just something to factor into comparisons. Many Ryobi people bend the reed stop out to allow the reed to open wider. Just make sure that it clears the crankpin by 0.020 or half a milimeter. The last Ryobi 31 that I measured had 150 degrees exhust duration stock. If you replace the thick cylinder base gasket with a thin one, you will get a little higher compression ratio. Maybe you should get higher RPM with your thinner air? Good luck.

Dave

Actually, I'm playing at sea level right now...

I machined out the squish band, and left out the base gasket completely, using only Yamabond sealer as I often do. This raised the compression but of course lowered the exhaust timing. I raised the exhaust port to get it back to 150 degrees timing, but left the transfers alone. I've done this on a lot of engines with good results. There is something I did forget when I got into a rush there at the last, and that is to check to see if the hole in the carb mounting matches the carb opening. If there is a lip there caused by the adapter being smaller than the carb, that could cause some turbulence and hurt performance. Also, when cleaning the plane up I see there is noticeable black residue, so I'm sure the ring still hasn't seated, though the Bowman rings usually seat very quickly.

I'll run it some more and get the ring seated and mixtures re-dialed in, and if it doesn't pick up I'll pull it off and check that carb adapter. I did raise the reed stop as you mentioned. Also, the comparison I made to the Echo engine... it is spinning an old Top Flite wide blade wood prop over 500 rpms faster than the Ryobi with a Top Flite Power Point of the same pitch and diameter. I really like the APC props and use them a lot, but these in these two cases; a Fokker Triplane and a Tiger Moth, the wood prop just looks a lot nicer.

Thanks for the ideas/help,
AV8TOR

Avator1977: Did you send a PM about a Echo engine? Thanks Capt,n[:-]

I sent you an e-mail. Did you get it?

AV8TOR

av8tor,i use the wood schimitar props on my ww1 era and planes that need that look.they perform just as good as the apc and they are wood.theyre also lighter and you get a little quicker spool up on acceleration but you loose a little of that heavy flywheel affect.

Well, I just got the tach and have some questions about it's use but This is what I Got from my 31cc, two ring,Ryobi with CH Ignition and Walbro WT644 carb. spinning a Master Air Screw 18/10 wood prop. I followed the GloBee instructions and held the tach behind the prop. about 12". The engine actually hit 7610 but it seems to hang around 7500 more. If anyone has experience with these tachs I would like your comments. Seems I can adjust the reading by moving the tack up or down. I have about 24oz. of fuel through the engine at this point. Do I need to run it longer before it is considered broken in?

It will take several tanks of fuel before the engine is broken in, and they usually keep getting better until after they have a couple of gallons run through them. Your rpms are pretty decent for that size prop and a new engine. Best to keep the Ryobis under 8000 in any case.

My Globee tach does the same thing. Very aggravating. I even made a little shield for the photocell hoping it would help, but it really didn't. I gave up and bought a higher quality tach.

AV8TOR

AV8TOR, It was suggested to me to rig up a MAGlite and point it at the front of the prop/engine while using the tach. The light should be pointed at the sensor of the tach. I intend to use a 20x8 or 6 Master Airscrew wood Schimatar (spelling?) prop. so keeping it under 8000 rpm should not be a problem. Thanks for your response.

Hi,

You can see if it will pull that large a prop. More normal sizes for the Ryobi are 18 x 6 to 10.

Good luck,
AV8TOR