Ryobi Conrod failure
 

Having read various posts on the the strength of ryobi conrods. I was flying my spad the other day when the engine went bang ,clunk ,clunk and stopped ,after making a dead stik landing I thought the engine might have sucked my butterfly screw in and done some damage which has happened before.After taking her back to the shed I pulled her apart and found that the conrod had let go. I always thought that the conrod was strong enough to handle just over 7000 rpm but won't trust them over 9000 rpm. This engine would have been doing between 5000rpm and 6000rpm when she went bang.Then I thought for a bit and that this conrod might have come out of a crashed engine and what happens when you go in nose first the crank shaft gets pushed backwards into the crank case and bends the conrod near the crank pin and I might have recycled this piston and conrod.

The only damage was to the piston,conrod,reedvalve.
Any way I found it interesting as I have plenty of spares and the engine is back in the air again.

Here are some photos ( I hope)

RE: Ryobi Conrod failure
 

Are you saying you don't think "GORRILLA GLUE" will solve your problem. Thanks for the pictures: FLATHEAD

RE: Ryobi Conrod failure
 

Every time I look at one of those Ryobi rods I am amazed that they hold up as well as they do...

AV8TOR

RE: Ryobi Conrod failure
 

Me too....

I don't think a crankshaft and rod can be made any cheaper than this.

RE: Ryobi Conrod failure
 

Looks to me as though something got in the bearing and locked it up at rpm?

RE: Ryobi Conrod failure
 

Take a Ryobi and machine a good rod from good aluminum...add the right size needle bearings. Then get that $15 reed valve kit for a DLE30and make it a more high performance engine. Use CD ignition & all the other tricks you can think of. May be fun & still not cost as much as some other over the counter engines. Hey AV8TOR....go for it!!!! Capt,n

RE: Ryobi Conrod failure
 

Unless you can devise this new aluminum rod for your Ryobi without much cost . . . .

It would be time and effort ahead to just substitute a DLE 30R for the Ryobi and throw the ryobi away?

Maybe an existing rod from another engine you have can be utilized?

RE: Ryobi Conrod failure
 

Well that wouldn't be any fun. I like Captain John's idea better, if I could ever find the time to do it...

AV8TOR

RE: Ryobi Conrod failure
 

Hello everyone-

I have repaired many of these 31cc engines in string trimmers and leaf blowers, and most of these were from the 1990's time frame. One thing I always noticed was the reed stop is extremely close to the con rod big end. All had rubbing on the reed stop by the con rod until flakes of chrome came off the reed stop then, more metal was torn from the reed stop, then the engine would lock up from the metal fragments getting into the crank bearing.

I solved this problem by using 2-3 gaskets under the intake block and sealing well with permatex ultra grey. I wonder if this may have contriburted to your rod failure. I found it impossible to remove all the minute metal particles from the bearing when this happened, so a new service crankcase would be installed (along with a new reed assembly, and careful check of the rod bearings). My old service manual for this engine lists some brush cutters models maximum rpm as 8,800, so I feel that the rpm isn't the culprit.

MTD sells an improved crankcase now for ~ 60-70 dollars, that is stronger than the older types, but you'll need the matching flywheel and module as the woodruff key location has changed.MTD-753-04328 (long shaft). Yes, it's not worth the time or money actually, but I really like this engine so I repair them when I can find one. [sm=49_49.gif]

RE: Ryobi Conrod failure
 

I'm not sure how someone can say the conversion engines "aren't worth the time or money". I have a Ryobi in my big 76" Tiger Moth biplane. It was given to me, and you can often find them for free or a few bucks at yard sales, swap meets, small engine shops, etc. It took me about an hour to convert the engine. I also put a Frank Bowman ring in it, raised the exhaust timing to 150 degrees, made a free flowing muffler, and added electronic ignition. It turns an 18 x 6 prop at around 8500 rpms and hauls the big Moth around just great. Level flight loops, Immelman turns, etc., and flies around at less than half throttle except when I am doing aerobatics. Total investment with the ring and ignition system = 80 bucks.

My brother has a very nearly stock Ryobi on his 15 lb. 80 inch wingspan Ryan's Rebel. It turns an 18 x 6 prop at around 7700 rpms and hauls the Rebel around just fine. Will loop from level flight at just over half throttle.

How can they not be worth using????

AV8TOR

RE: Ryobi Conrod failure
 

Sorry to offend you. I have a Ryobi type 31 that started life as a Lawnboy. It is stock and does an 18-8 just a little over 7000. I'm sure it would do 7400 with just a 11mm carb? On the Lawnboy, the muffler was already rather open with a single 1/2" outlet. I replaced the lawnboy as a weed whacker with a Ryobi in 1998 and the Ryobi still runs fine.

What prompted the comment about the DLE-30R was the statement about making a needle bearing aluminum rod for a Ryobi. If you start dumping a lot of money into one, you may as well buy an engine that runs pretty good as is.

RE: Ryobi Conrod failure
 

Hey Ave8tor, what I mean is it's not worth it to most people to spend money repairing a string trimmer or blower with parts that cost as much as a new machine, my post is not aimed at rc conversions directly, just relating some of my experiences with this engine as it relates to con rod problems, thanks for all the data on your airplanes anyway.

RE: Ryobi Conrod failure
 

This ia a conversion thread/forum. To say any engineis not worth converting is just not the right place. Hey this is what its all about. I am sure a lot of "over the counter" engines have been converted somewhat to get better running. The person who put that statment there should remove it. ......w- - e
Then I will change this post....by edit backspace...then insert new post....Done Capt,nhttp://www.rcuniverse.com/forum/js/f...ngry_smile.gif

RE: Ryobi Conrod failure
 

w8ye meant the time and money involved in making a new rod and crankcase, for someone wanting to do the work it's worth it, but not the best investment you could make, not that converting them isn't worth it...

RE: Ryobi Conrod failure
 

The way I look at it for some people its the journey not the destination.

Adrian.

RE: Ryobi Conrod failure
 

<hr />First you do not worry about the time...if it is something you kike to do.

It may be possible to find a rod close enough to machine to work.

You do not need to make a new crankcase....just the rear crankcase cover plate needs to be made or again redone to use the DLE reed box.

This is for the guys that know this can be done......for the rest ....don,t say its not worth it. Let the each guy decide that for himself. Capt,n

RE: Ryobi Conrod failure
 

I just meant I knew what he meant, I understand the drive to do it yourself too...

RE: Ryobi Conrod failure
 

Sorry if I kind of "went off" there... Didn't really mean to. Anyway, there is a big difference in having a rod made by someone, or doing it yourself. I would do it myself, and consider the "work" as part of the fun and of the hobby.

Anyway, it's all good.

AV8TOR

RE: Ryobi Conrod failure
 

Actually it is and you can.
When you are charging/barter someone to convert an engine for them, its important to consider the cost going in and exiting.More often than not you will recoup more of what you spent by using an off the shelf solution than a conversion when selling the plane or engine.
Some guys want to use a particular engine for the sake of using that engine, they have no choice but to convert it, but for someone just looking to power a plane. They can grab a Zenoah cheap, bolt it on themselves and it will retain most of its value after a season.You can spend more on a conversion and wait forever to find the right guy to buy it for 1/5 of what you have into it.

RE: Ryobi Conrod failure
 

<div style="border-bottom: medium none; text-align: left; border-left: medium none; background-color: transparent; color: #000000; overflow: hidden; border-top: medium none; border-right: medium none; text-decoration: none">You can spend more on a conversion and wait forever to find the right guy to buy it for 1/5 of what you have into it.
</div><hr /><div style="border-bottom: medium none; text-align: left; border-left: medium none; background-color: transparent; color: #000000; overflow: hidden; border-top: medium none; border-right: medium none; text-decoration: none">I do not do conversions to sell....I make them for my own use. I have some engines I will never sell &amp; I think most guys also do/make conversions for there own use. Capt,n


</div><hr />

RE: Ryobi Conrod failure
 

I do it for a handful of freinds who don't have the ability to do it themselves.
Conversions are only cheap if you do it yourself.