Engine Thrust Bearing

[FuzzyDriver]

I took photos of the cover's crank-sides to show the difference between the bottom (i.e., blade end, left photo) and the top (i.e., flywheel end, right photo). As you can see, the bottom end is shiny from the crankshaft rubbing on it and the top end not so much, apparently rarely contacting the crankshaft.

Wear marks on the other cover (not shown) indicate the thrust bearing was bearing on blade end of the cover. I did not expect this, it makes more sense to me that the thrust bearing should bear on steel surfaces, in other words between the crankshaft and the washer (shown next to thrust bearing in above photo), with the washer against the cover, but not turning, of course. Instead, the washer was against the crankshaft. ??

 

[FuzzyDriver]

According to the manual, I listed crankshaft end play, which is crankshaft movement up/down with the engine properly mounted on the deck. I really don’t understand what you mean or where your measurements are for. Maybe this manual will help, it’s where I got my specs from. https://lookup3.toro.com/ttcGateway/acrobat/manuals/lball64.pdf

I missed your reply initially. Sorry about that. I have a printout of those spec sheets, and depend on them a lot. And the end-play spec is just what you thought it was measuring, rather than what I thought it was measuring.

Here's where my error was, and I'm surprised that no one pointed it out (or perhaps no one was aware of it). By studying the photos of where the crank meets the case and where the crank meets the cover, it dawned on me how VERY different the surfaces look. The crank contacts the edge of the case, but contacts a large surface on the cover. As shown in my photos, I was taking the measurements with the cover removed (else how did I get the photos?)

SO...I (temporarily) installed the cover and THE END-PLAY disappeared to maybe .010". Totally unexpected...the COVER is the bearing surface??? But that's exactly what I'm seeing: End-play goes from .1625 to .010 when you install the cover.

Now, honestly, guys...did ANY ONE know that?

And why is it this way, so you can restore out-of-spec end-play by changing just the cover?

 

[Rivets]

You must ALWAYS measure end play with the crankcase cover installed. I assumed you knew that. Sorry about that. On many Lawn Boys getting end play back into specs a thrust washer can be installed between the PTO thrust surface on the crankshaft and the crankcase, but replacing the cover. If you are getting an end play of .010, you are within specs and there is no need for a thrust washer.

 

[FuzzyDriver]

Ah...ASSUME,.. What does that stand for again? Heh heh...just kidding around. I hope that in the future someone else fooling around with a Lawn-Boy engine reads this thread and saves themselves a ton of trouble!

Thanks for sending me down the right road and have a great day!

 

[bertsmobile1]

Never forget that these engines are made as cheap as mechanically possible while still allowing the engine to run
Thus things like end play are done with gasket thickness where possible And thrust washers or thinner gaskets to accommodate for wear.
However by the time you need a thrust washer generally the top bush is flogged out oval
If they wanted to make a good mower, it would have a ball bearing on the PTO end to locate the crank & a roller at the flywheel end .

 

[FuzzyDriver]

Never forget that these engines are made as cheap as mechanically possible while still allowing the engine to run
Thus things like end play are done with gasket thickness where possible And thrust washers or thinner gaskets to accommodate for wear.
However by the time you need a thrust washer generally the top bush is flogged out oval
If they wanted to make a good mower, it would have a ball bearing on the PTO end to locate the crank & a roller at the flywheel end .

F-engines have roller main bearings at the bottom and top ("top bush"), needle bearings on the connecting rod at the crankshaft and at the wrist pin. Where would you put more bearings?

Ball bearings would not be better. Neither ball bearings, nor straight needle bearings affect end-play, they would have to be conical needle bearings like on a car's spindle or thrust bearings, which one of my F-engines actually has. They have more real bearings (vs brass sleeves, etc.) than any other mower. They were made to be as reliable as possible while maintaining low weight. None of the engines I'm working on are less than 30 years old, and never needed to be torn down until now. No other mower lasts anywhere near as long. And these Lawn-Boys could well be running fine 30 more years from now.

"If they wanted to make a good mower" Whaaaa???? They were the highest quality mower you could buy. People were jealous of neighbors with Lawn-boys! This made it a two-edged sword: They cost more than other mowers (where people go to WalMart and shop ONLY by price) and last nearly forever, the combination of which reduced sales too much.

 

[bertsmobile1]

Victa was using 3 ball bearings back in 1956 and continued to do so till 1978 when the overhung crank Power torque engine was developed that used 2 ball bearings till 2020 when B & S shut the plant down.
Both engines ( or the mowers they were attached to were deemed to be too dangerous for Americans & after some considerable pressure Canada also stopped importing them
Villiers engines used ball bearings as did Suzuki but I don't know if any USA local makes used those engines.
BSA used balls at one end & either balls or rollers at the other in their industrial engines as fitted to Ransom & Marles reel mowers . BSA sold their industrial engine division to Villiers back in 1962 but Ransoms bought the rights to make the engines themselves & continued to do so in the same design till they were bought out in 1991.
Sachs used balls both ends which were fitted to a very large number of European made walk behinds virtually till Husqvarna was split off from Sunbeam ( there was a tie in there somewhere , probably through the Dolmar chain saws ) .

The good citizens of the USA have always been lied to big time and in many cases forced to use inferiour locally made products because governments were in the pockets of the manufacturers or the investment companies who had shares in the manufacturers .
The Chinese ( pre revolution ) invented entire population brain washing and the USA advertisers perfected it .
On a world wide basis Lawn Boys were in the medium to OK quality range but never top shelf anywhere except in the minds of Americans.
Not trying to rubbish them, there is nothing fundamentially wrong with them as they were well built, just built down to poor design.

Ball bearings self align when they rotate and are used on a massive number of electric & petrol engine to maintain end float
All of those parallel twin engines listed earlier .
Norton used super blends right up till the end & they are a compound bearing with both balls for alignment & rollers for load carrying
Honda had balls & rollers , Generac had balls both ends , Wisconsins have balls both ends
That is about the limit of the brands I have pulled down but I am sure there are others

If you can't see it, the simple system goes the crank is pulled down hard onto the inner race
The outer race is locked into the crankcase so the crank can not move up & down ( or in & out for horizontals ) any further than the play in the race .
Very simple but does require machining to =/- .0005" which is harder ( thus more expensive ) than most would believe and quite expensive to do till industry switched to carbide tooling &/or real time computer control

However in the case of the US manufacturers , no excuse for not doing it has they made hundreds of thousands of engines for aeroplanes during WWII and most of that precision equipment was made redundant by the invention & use of jets post WWII so the gear & technology was there , just investors would rather spend it on advertising than quality manufaturing .

 

[FuzzyDriver]

Fascinating Australian small engine history you know, Bert. Though I read it carefully, I didn't see any mower engines with four (or five (counting the thrust bearing) ) needle (or ball) bearings. Which of these engines were on mowers and were better than Lawn-Boy in reliability and/or weight?

 

[bertsmobile1]

The original engines were very much styled off the current Villiers at the time
The theory was villiers had contracts with other companies who made reel mowers and they did not want rotaries to challenge them
So Merv made his own.
My fathers 1862 model is still running , still on original bore and still gets used to mow the common areas of 5 blocks op flats ( appartmants to some ) .
The powertorque was the best engine ever made and only has 2 bearings
I have just mowed 3' tall tussock grass with one of mine for an hour and that is a 1986 model
Sold 3 used ones last week , all from the 80's & 90's . all on original bores and all running perfectly
Top of the engine is 4" to 6" lower than anything with a B & S or Honda engine on it .
There is nothing wrong with Lawn Boys , just like there is nothing wrong with Snap On tools.
But the high price is the result of market hype not outstanding performance
Then you add features that make a real difference like the carbs that can never varnish up & clog even if you forget to turn the fuel tap off .
Throttle cables that run internally down the air filter snorkel so unlike everything with a sprint / quadra / Europa engine on you don't mash up the throttle linkages when you mow under bushes
Then there is the snorkel itself , LB did for them to some models as well but clean air, so you never wear the bore and rarely ever have to change the air filter
Swing back blades.
engine strips down with nothing more than a No 3 posidrive screwdriver
Carb is a bayonet fitting so come off with a twist
Governor is phneumatic so never clogs blocks or breaks
Decompressor is also phneumatic so again never gives any problems and usually last around 30 years when it will need a new diaphragm &/or spring .
Cooling air blows down under the engine so assists with the catching
Exhaust blows down under the deck so reduced noise ( LB did that with some too from memory )
Muffler is clipped on, so no rusted in then broken off muffler bolts
Periodic servicing is replacing 5 X O rings and 2' of PVC fuel line
Then every third one replace or repair the decompressor
And of course despite what the marketing department foisted on them they will happily run on 50:1 which is what I have been using for 40 years and according to Victa, if you use their super duper branded oil ( thus very very expensive ) you can run them 100:1
Cut off switch is also enclosed inside the carb so it can not get affected by weather or debris build up and you can actually mow under water ( did it to win a bet , got very wet ) but being totally enclosed no affected by heavy rain dust storms or even snow .
And being all cast iron, apart from the alloy head, & zinc pull start easy to make , suffers no heat distortion & economic to recycle

There is more to engine quality than the number of bearings although absence of them dose lean towards the lack of longevity .

 

[StarTech]

Now I know why your mowers have snorkels, Just got mow when the ditches are full of water and to take a shower at the same time.