RE: General port timing guidelines?
 

Some of the Ryobis have a pinned ring whereby the pin is the full depth of the ring land. This makes for a very wide ring gap by necessity as supplied originally. You can carefully grind the pin down half way into the ring land, then have Frank make a custom ring the has notches that go over the pin. Then the gap can be set very tight, even zero gap as recommended by Frank. This will help power a LOT on a Ryobi. Frank will modify pistons and pins for customers if desired.

The Ryobi will also like an 11mm carb and a free flowing muffler. Hopping up an engine is always a coordinated effort. Doing just one or two things seldom has the desired results...

AV8TOR

RE: General port timing guidelines?
 

It is possible someone did mods to the Homie. It was a bare engine, not a whacker when I got it. I would try one of the Ryobis except the cylinders aren't the best. One is really scored but the other would run just not sure how good but it does have a offset pined ring.

RE: General port timing guidelines?
 

Try to start with good parts. These things are too cheap to find to be hassling with less than perfect parts going into the project.

The Ryobis run good, and are nice for a narrow cowled airplane like a Tiger Moth biplane or a Mustang. But if you are after high power and rpms, then go with the Homelite 30cc or find a 30cc Echo. (The Homelite 33cc engines out of chain saws run well too.) The Stihl 25.4cc engine is another good one in this size range. If you can find an Echo 23.6cc engine, they are very lightweight and make very good power, especially when modified. I have one that turns an APC 16 x 8 at 9000 rpms. (It is hopped up...) They came in PB-2400 blowers and other Echo machines in the mid to late '90's.

The Ryobi is power limited by the stock stamped steel rod. If you run them over 7500 rpms for very long, they'll blow....

AV8TOR

RE: General port timing guidelines?
 

The Ryobis that I acquired are the newer model that are like the Homie, not the older 31cc Ryobi with rear Int. and Ex.

RE: General port timing guidelines?
 

Well, I took the leap and I changed the exhaust port timing on my Homie 30. I raised it from 130 to 140. However, I didn't see any improvment in RPM. I was hoping for a couple of hundred. It still runs 6600. (Maybe thats as high as my tach goes)