I was at Wally World tonight and noticed that the 31cc Ryobi-engined Yardman and Snapper trimmers now have integrally cast flywheel housing backplates instead of the tradional Ryobi bolt-on backplate. Hope this isn't a trend to come for all 31cc Ryobi-powered trimmers...

maybe they'll be even cheaper now.
i bet they do a plastic crankcase next

dave

It's no big deal to grind off the excess aluminum bracketry. I've done this on several different engines. The only negative is that the modified engine can no longer be put back into weedwacker duty - never a problem in my book.

Actually, I wouldn't mind a composite crankcase if it means lighter weight.

Yeah, I agree it's no problem removing metal. But considering the work of removing metal on some engines (and I have a milling machine to help) it's still nice just to be able to unbolt a Ryobi and be looking at a nice compact case -- with 2 hours left over to go turn prop drivers, mow the yard, fly airplanes, etc...

I wish I had a milling machine. Between an air cut-off tool, an air grinder, and my dremel tools, I manage to do a half decent job of trimming unecessary metal off engines. My results usually look ugly as sin, but functionally work just great. I suppose I can spend more time to pretty things up, but like you, my time is spread mighty thin as it is...

They may not be called Ryobi anymore but I saw a Weedwhacker in Lowe's in Wichita Falls, TX that had the detachable front plate. I dont remember the name but a Ryobi by any other name will spin just as fast.

They're marketed as Troybuilt here in So Cal. Ryobi is still here also, but the older 2 strokes don't pass emissions, only 4 stroke and the new CA compliant models....$100+

Are you sure that the wal mart snapper and yardman weedeaters use Ryobi engines? Are they 2 strokes?

coomarlin:

Well, I'm 99% sure based on the following:

1) They're 31cc
2) Same Ryobi 2-bolt cylinder casting
3) Same looking crankcase except for integral fan housing backplates
4) Carb & muffler both on rear

I'm not aware of any current trimmer engines other than Ryobi that have both the carb and muffler on the rear. Yes, they're both 2-strokes.

Anyone do the conversion on one of these newer engines? I picked the snapper 31cc up clearance and was wondering what the results were.

Haven't broken it down at all , so I haven't seen the issues yet.

-Steve

Yes, a friend of mine has converted two of these engines. One is for him and one for me. He milled off the flywheel housing flush with the crankcase about even with the front of the cylinder head cooling fins. We are using C&H ignitions for the planes they are going in so it leaves a nice round section right behind the prop adapter to clamp the pickup to. Kind looks like a big glow engine or a 3W when done. Suppose you could put the stcok ignition back on after doing the milling if you don't want the cost of the C&H. In my opinion the new two ring engines performance far outweighs any work required for getting rid of the housing. It's well worth it. I bought a yardman trimmer about a year ago that had the two ring piston but the old bolt on housing, so apparently there was a period of transition. I would imagine if one looked around they might find one of these transitional trimmers. I paid $79.99 for it. It is currently turning a 18x8 MA wood prop at 7200 rpm on a Hangar 9 PT-19 at 14.5 lbs. Flies it very well at our field which is 5200' in elevation.

Great to hear. Thanks for your report!

I've never done any milling but perhaps I could come up with something to make it workable. Time to break open that box I suppose and see what is really there.

-Steve

Okay.. here is what I found. Not sure if it's ryobi (this is in a 31 cc snapper from this past season that went on clearance at Wally World)

Muffler and carb are on rear. The carb is mounted to the back plate of the engine crank case, however... this cover (backplate) is very large and would have to be cut down to be flush with the crankcase itself.

Muffler doesn't use screws to hold it on. It is held on with a spring on either side of the cylinder head which clamps the muffler to the head. Exhaust port itself is recessed into the head. Muffler has a tube extenstion which presses into this exhaust port.

The front of the crank case is wide and would have to be cut down to look correct.

People mention the Ryobi engines now have a double ring... where are both rings... both at the top of the cylinder? I only see 1 ring at the top of the cylinder through the exhaust port. No other ring is visible.

Bolt pattern at the back of the crankcase is different (mounting area) than the square 4 bolt patern of ryobi. Also, the cylinder head looks different and attaches differently.

This must be some other animal.

It appears there is another current engine in the Ryobi configuration that is also 31 cc. Original clues pointed to ryobi, but this does not look to be.

-Steve

Hi! That sounds more like a Poulan built Weedeater engine than any Ryobi......Bob

So Poulans have the muffler and the carb in the rear?

Okay... you were correct! It's is Poulan from other pictures I now found. Thanks for pointing that out.

SOOOOoo... just so everyone knows, the Snapper 31cc appears to be a poulan. The pictures look exact. Bolt pattern, shape... flange... everything.


-Steve