Where its an open chain, waste oils like the sticky chain bar oils tend to be the best. Normally oiled before use. The Simplicity has a Tecumseh diff and that horrid little bit of work tended to be the standard Holden slop fit. That help cause it to shear the bolts on the driven sprocket & rather explained why the driver was floating on a spline. Transmission is a form of steering oil pump.

I got savage with it dismantled it and used the lathe to shear thirty thou (inches) off the housing to tighten it up. Also taking the opportunity to improve the lubrication. As for the driver sprocket, that may be similar to what you have? Driver is around 43mm (worn) nine teeth.

On each side to improve the tangent are two 37mm dia. nylon rollers that are now the third set as I made new ones when I sorted out the sprocket failure. Those form a jaw on a rocking arm relying on a large tension spring to pull them together to tension both in forward & reverse: That being done hydraulically. I got the new spring at an industrial supplier as both originals were too straight & got cut through.

With the type of punishment it cops the lower deck bearings (3 of six) are usually chopped out in 250 Hrs. The motor at over 1000Hrs is getting tired. However, at the end of a session, usually hrs. it is blown down with compresses air and the air cleaner checked and the pre cleaner usually needs cleaning. In dirt oil change 25Hrs.

Honda push mower 1989 much the same treatment. Dirt is the killer. With the exception of two new Honda motors everything runs on tractor oil (R4 Diesel spec) Old engine oil is too thick and makes it hard to start. Both it and the Ute tend to be on a two year oil change cycle. Ute motor is first life (1958) and the bottom end in the tractor (Petrol Kero) is original (1951). Never change the oil & not the filter.

Part 2 uploaded.

Just to finish this one off and get back to radio projects.
The Ryobi is on the scrap heap.
The fault causing the engine failure is principally the timing chain, chain guides and tension spring are all worn to excess.
The option of buying new parts may have been easy 10 years ago but not now.
The engine is obsolete and parts places around the world have either quit the engine or want high to silly prices for parts.
Second hand engines are non-existent or come at silly prices.
I could buy a new China horizontal engine for about $240 and mount that up with a bit of engineering to the old base.
No!


If it was a rare Vintage engine and we wanted to get it running for display this could be done.
I would re-make the chain tensioning system to accommodate the loose chain by engineering.
That could be re-surfacing the guide wearing faces with plastic, increase the chain centre distances, wind a new tension spring and so on.
This sort of thing I have done elsewhere.
It's not a rare vintage engine but a piece of short life high strung crap.

The solution is,
1/ wheel it out to the scrap heap where it gets used for bits for something else or goes to the tip.
2/ buy a current 2024 18" mower mulcher (Victa/China) at around $500and SERVICE the thing.

End of story.

Fred.

Its rather rare to see small engines with a chain drive anywhere most early ones were gear driven side valve and later push rods to OHV still gear driven. The chain saw chains will jump with damaged guides & too slack. They do that usually after they have gotten really hot cutting red gum with insufficient oil to the chain.

Servicing the small mower, by cleaning the air cleaner especially when there is dirt & dust and the outside to keep the air vanes clean, goes a long way toward unit life. As noted before the Honda push mower here is1989 vintage and still taking a hammering.

Forgotten with this type of motor, they are unlike unlike the car, but more akin to the aircraft, tractor & ship engines. They are designed to run at a specific speed and have a governor to maintain speed. Running these engines below the recommended speed can kill them. If they are from a good manufacturer, they are balanced to run at a recommended set speed when working and that will give optimum life.

Marc

Yes Marc, I have some old Briggs side valve engines from the 1960's that could be resurrected and put back in service just for fun.
Things may be worn on them, but they would run if just cleaned up and prepped carefully.
The valves and governor are gear wheel driven on Briggs and never fail.

The evolution of small engines seems to have shifted to fuel efficiency not life.
These China engines use cross flow hemispherical combustion chambers with large valve to chamber ratios.
That sort of thing you only used to see on race engines like dirt track and circuit racers.
Now the cheapest motor bike would have such an engine precision machined and far more power than the things I rode.

This mower engine is a master class in combustion efficiency with just enough metal bits holding things together.
The only good bit of engineering is they use a large ball race on the flywheel end.
Smart enough to realise that is the Archille's heel of small constant speed stationary engines.
You may think the drive end of the crankshaft has the highest loading what with belt pulley drives or pumps hanging off them.
However, the rotating forces being nulled between the flywheel and crank are enormous and the vector results can just chew a plain main bearing out much quicker than the rest of the engine.
How do I know? I did life tests on SV engines way back then and the plain rear main on a Briggs would chew out well before the ball bearing at the front. That was the advantage of the Robin, Kawasaki , Honda jap engines. They used ball bearings front and back and rod and were forever motors.

Anyway that was back in the Jurassic days and this is a radio forum!

cheers, Fred.

Fred:
As a final note some B&S engines were a nightmare & I had a Chinese copy of one come in and it had done exactly the same as the B&S it was copied off. Threw the governor weights which had a habit of leaving a big hole in the crankcase. Oldest B&S engine still in service here is 1979 and its side valve.

Marc

Just when you thought it was safe to get back into the water!!!

I have a part three to this story.
A Masport "wreck" going to the tip found its way into the workshop and will replace the Ryobi.
Actually a very good piece of kit once 10 years of storage was fixed.

I'll send the usual PDF to Brad, and I promise no more mower stories!

Fred.

Part three uploaded.

Better remind him to check the oil level before each run!
Do that, clean the air filter and it will likely last many years.
Until we're not allowed to use them, like backyard burn-offs and incinerators!

Yeah Ian those Briggs side valve engines were great but of course could not meet emission regulations going into the 90's.
Hence the demise and the rise of the short life 500 hour OHC cross flow China engines.

Same with Lister diesels, the long lived traditional air cooled types just could not comply with the noise and emission regulations.
Engines that would run forever when serviced regularly, we would see 20,000 hours or more on well serviced units.
Some of the older engines our great grandads had literally ran for ever doing pumping duty, 30 years was not unheard of.
Thats 30 years continuous, try doing that with your "what-ever-you-get" nowadays.

Yes they blew black smoke, barked loudly, drank fuel but of any crap grade, did not have much horse power but just went and went.
They ran from the Antarctic covered in ice, to Saudi Arabia hot as hell and the toughest gig of all, Australia.
Oh dear that's old man rambling!
Fred.