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Ryobi 26cc Four-Stroke

Old 01-24-2024, 03:35 PM
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Thank you for all the info on 4 stroke carbs....

It’s spring 2023 and I just got a NIB Saito FG-20 from a fellow hobbyist. He had bought it a decade ago to go in a Unionville Hobby 8ft Radial Beaver that he never finished. I was very exited to check out a spark ignition gas fired 4 stroke.

After reading all the problems on the Internet forums, I considered selling it as NIB. I was looking for a reliable fuel fired engine for reliable winter flying. So one day I decided to break-in on a test stand and see what happens. I know the internet community has many warning of how difficult they can be to run and tune.

The break-in (per Saito instructions) went surprisingly well. I couldn’t believe how little gas it used, even at a rich setting. I fouled one plug, but otherwise OK. I installed it inverted in my my “beater” SIG Kadet Senior. The first two flights went well, but on my third flight it would not transition to mid or high speed. I played with the carb tuning to no affect. Now at home it would’t run smoothly on the ground. I changed plugs, took to the field a few more times, sometimes I didn’t even get in the air. Then a few days later it would run Ok on the ground. Not consistent. And always black soot coming out of the exhaust.

My assumption was carburetor problems. I dismantled the Saito carb and saw no issues. So I bought a Ryobi 30c 4 Stroke trimmer carb from Amazon. I made an intake manifold adapter to trial this out. It worked way better, no black soot. So I took it to the field twice. Both times I had to change plugs to keep in running smooth. At this point I was on my 5th plug! After one of the plug changes the engine ran like a Swiss watch. The lightbulb come on…. My problems were also ignition.

I took it home and ordered a Rcexl ignition from Aliexpress. I was able to install using the universal sensor mount, and drill and tap one additional hole in the crankcase to get 28deg BTDC. I also bought the alignment tool.

Off to the field this Sunday. Beautiful sunny winter day -10C(14F). Six 4-5 minute flights with no issues!!!!!!! Idle good, transition good, high speed good. No dead sticks. Sigh. Finally.

The manifold is a 3/8” ACR copper street 90 silver soldered to a brass plate.

Sorry, I can't add photos. I need 10 posts first

Last edited by RobJD; 01-24-2024 at 03:38 PM. Reason: Can't add photos

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