# 31cc inverted-cylinder trimmer engine origin?



## mexicanyella (Sep 29, 2015)

Since the early-mid 80s, when my grandpa bought a new Ryan 31cc trimmer, it seems like the consumer-grade trimmer market has been flooded with various names of trimmers all including the upside-down 31cc engine somewhere in each manufacturer's lineup. Lots of tan/brown Ryans there for awhile, then a color change and a name change to IDC somewhere in the early 90s, then another name change and slight housing change to Ryobi, and since then Bolens, Troy-Bilt, Poulan Pro...all offered a trimmer model with the tank on top, cylinder on the the bottom, reed valve, carb and muffler out the back. Cantilever crankshaft. Finally it seems that engine's been phased out of new production, but there are still zillions of them on Craigslist or in dumpsters.

And this summer it seems someone's installed a homing beacon in my garage, calling them from all corners of the globe to come here and retire. I had five of them already--plus a Troy-Bilt blower with the same engine--until a Ryobi 740r trimmer, missing its carb and rear heat shield, showed up unexplained in my driveway this evening. Unsettling. How'd it get here?

I always thought these things were pretty lame trimmers, based on other people's comments and remembering the weight and vibration of grandpa's Ryan. But after getting a 31cc Poulan Pro and a 31cc Bolens running recently, I've discovered that they're pretty easy to work on, easy to get running (carbs, fuel lines) and once running and tuned, they start easily and swing a dual-line head loaded with .105" line with authority, and at a fairly low rpm. I kind of like them now. And it seems I have a lot of spare parts accumulating.

Anyway, my attempts to learn about this engine design's history have come up empty. I just find references to their use by large-scale RC airplane guys, or people complaining that they can't get them to run. Can anyone reading this shed some light on this engine design's background, country of origin, etc.?


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## ncpete (Oct 21, 2015)

Don't know much about the history, but my Ryobi with the 31cc powerhead survived 19 years of homeowner use, and 1 summer of commercial work I put it through. suppose, if I went out and really looked at it, I could get it running again with a fresh carb, fuel lines, and spark plug.


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