# Ryobi 31cc weed wacker. snapped rod.



## clintonior (May 13, 2013)

Is this a good ole motor? It looks to be better built than the newer 25cc jobs. this has expand it and was thinking ill get a piston/rod for it and make this my trimmer.?


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## LegDeLimber (May 13, 2013)

promac850 posted a pretty good thread on porting his Ryobi top cylinder.
http://www.arboristsite.com/chainsaw/168235.htm
If that's your version,It might give you some views of the guts and help decide.

Got any pics of the victim? 
how or where did the rod break and what other parts 
got smacked by the loose ends?
anything else scored or bent, cracked, etc..?

Is it the motor the type with cylinder pointing down or up?
I believe they were built by the same company as Homelite 
when it was changed to the upward cylinder.

31cc makes me think it may be the downward cyl.

On the upward ones, Ryobi used *30cc and changed to 26cc
but kept the same model designation (i.e. "cs30") before changing
over the model labeling numbers.
(*not certain of exact cc's on the 30)

I was planning on digging into the top cyl 30cc ones this summer
but bum knees (and prob surgery) have put a crimp on those plans.


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## Miles86 (May 15, 2013)

Howdy:

Did it break on the 13th? :rolleyes2:

OK, I have worked on these 31cc, and it has been around in production since the 1970's !
Cantilever crank with laminated steel flyweight, reed valve, and many small changes over the years to the porting etc...
Early versions are 2 channel and higher compression ratio, no decomp slits in the transfers.
Some have an EZ in the model number that means it has compression relief slits at the top of the transfer ports.
Some cylinders are two channel transfers, some are 4 channel transfers.
Early crankcases have a removable flywheel shroud, the more recent versions have the shroud molded as one piece with the crankcase- these also mate up with the 4 channel cylinders.
The reed valve backup plate on some units rub the crank pin and eventually fail and destroy the cylinder and main bearings from all the metal frag. The can also break the rod from metal frag. 
I use small brass washers under the reed block to space out the reed from the crank, this works well.(Need to seal using yamabond 4 as gasket will no longer work).

They should not be run faster than 8000 rpm. Normal is 7200-7500 rpm. Always loctite every engine screw and bolt and use a gasket dressing on the cylinder gasket.
This is my personal experience, most people just throw them away. 
The are a pain to work on but I like these for some reason.

I have one from 1989 a blower vac, still running great.


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## josh1981 (May 16, 2013)

Get a Stihl fs90. Or km110r kombi with string trimmer attachment mine has been great!


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## jughead500 (May 17, 2013)

i just got 3 of those yesterday.1 ryan,1 IDC and 1 later model ryobi probably mid to late 90's.i can part it out if the crank is good


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## clintonior (Jun 6, 2013)

sorry for the delay I finaly got an engine of ebay it has the bottom end. my original jug had the decomp slits one on each side. I re used my bottom end . once back together it fired and stalled then the recoil rope snapped so it took a day or two to get the rite cord. now back together it runs but has a vibration so mabye the rod deformed the crank a bit. the new short block came with a bottome end so this time i think i have to pull the whole thing down and swap it out this would be a good time to lock tite it as i did not. also i didnt use yamabond on the reed block. the crank contacted the reed stop i bent it back into a shape mabye not the right one. but i would like to make sure it dosent contact the con rod . :biggrinbounce2:


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## Miles86 (Jun 6, 2013)

Hey-

Nice, I like these , and once you get them set right they are very tough and just feed it good oil and it will last. ( Newest versions with the quad ports and the 1 piece case are the best.)

I like the Mystik HP Ultimate 2 stroke oil, also using the AeroShell Sport 2 aviation 2 stroke oil, I like this a lot.


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## clintonior (Jun 7, 2013)

I want to find mistik oil in my area but no luck so far. TSS has their grease but doesn't stock their 2t yet.


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## Miles86 (Jun 7, 2013)

clintonior said:


> I want to find mistik oil in my area but no luck so far. TSS has their grease but doesn't stock their 2t yet.



Hey- 

Not telling you what to do of course, but TSS is never going to have the good stuff.

I use this easy and fast to my door-

https://www.mystiklubes.com/do/product/663096002

(I have no connection to Mystik)


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## FergusonTO35 (Jun 7, 2013)

I have a couple of Ryobis in my parts pile. I think one has the upside down cylinder and the other does not. If anyone wants parts or the whole thing they are yours for shipping.


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