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The crankshaft on one of my self-propelled mower's engines has a thrust bearing and washer between the radial bearing and crank. This mower had a pully on the crankshaft to drive the self-propelled assembly. I don't see anything in any of my service manuals about a thrust bearing, even on self-propelled engines. The engine I am building right now is a regular push mower (i.e., not self propelled). Would the thrust bearing make any difference on a non-self-propelled engine? I put it on temporarily to check it out. The engine case that originally had it has wear marks where the crank had been pushing down (towards the ground) on it. Anybody got any experience with these thrust bearings? Chuck it or install it? I'm leaning towards leaving it off since it didnt have one to begin with, but I'd like to get useful input especially since it may help future Lawn-Boy engine builders. I always wanna help!

I took some measurements on crankshaft axial end-play. Since the bearings do not lock the crankshaft axially, crankshaft up and down movement is limited by physical contact between the crankshaft and engine case. I got 0.1625" full travel (See "Crank Down" and "Crank Up" below). Gravity and blade lift will tend to pull this down (during operation). Is this acceptable? This does seem to be a reason for the thrust bearing I found on one engine (see photo below). Has anyone seen this before? I would appreciate input from anyone. Should I put the thrust bearing on this engine, even though it originally didn't have one? Thanks!

You need to find a service manual for that the engine you are working on. I am fairly certain that 0.1625 is quite excessive. Briggs engines are usually under 0.030 max on end play. So yes it may require shimming with the thrust bearing provided it is sized correctly.

I would look for a manual but right now I got a problem headache which woke me up. It making it difficult to concentrate. I going to lay back down in a dark room.

What limits the B&S end-play? Do they have a separate thrust bearing? Or conical bearings that lock them axially? I added photos to my above post so you can see the difference since, as I understand it, you don't work on Lawn-Boys.

Which engine model are you referring to?

FuzzyDriver said:

What limits the B&S end-play? Do they have a separate thrust bearing? Or conical bearings that lock them axially? I added photos to my above post so you can see the difference since, as I understand it, you don't work on Lawn-Boys.

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Correct they were before my time in this business. It does appear you have a "F" engine. The only Lawn Boys that I have worked are late models with Kohler engines. And those engines are not rebuild-able when you need to over size the cylinders.

Hopefully someone else here has the knowledge needed to help you.

If he has an F-Series engine, crankshaft end play is .006”-.016”.

Rivets: It's an F-engine, but I'm pretty sure we aren't talking about the same thing. .006 to .016 is surely the connecting rod endplay on the crankshaft, right? I'm talking about how far you can slide the crankshaft back and forth through the main bearings, as shown in the photos above. If I'm wrong, then please educate me on what keeps the crankshaft from sliding back and forth through the mains, I'm really having an issue understanding this - or, for that matter, if it even matters.

This is a larger issue for me to understand than just this engine. My 'daily-driver' crankshaft has been migrating up slightly so the flywheel is starting to "ting" against the pull-starter assembly on top. Not continuously, but when I hit a bump at higher throttle.

StarTech: I watched a B&S video that included checking and setting instructions for crankshaft end-play. I don't see how it could more different than Lawn-Boy. 8^S On the B&S, crankshaft end-play has a .002 - .030 spec and the engine splits axially, so you set crankshaft end-play by changing the thickness of the gasket (wow - didn't expect that). : ^ )

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 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. ??

Rivets said:

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

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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?

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.

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!

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 .

bertsmobile1 said:

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 .

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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.

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 .

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?

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 .

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.

Some people have a problem between differentiating between top quality & marketing hype so they pay $ 100 for a wratchet which breaks so they tank it back & get another and another . Others can work out what quality is so pay $ 30 for a wratchet that last forever.

FWIW ask an Aussie and they will come back with Scott Bonnar , Honda or Pace as being the best , simply because the advertising said they were and their prices are higher .
Like I said, nothing wrong with Lawn Boys apart form the name inferring a slave mowing your grass ( for those looking for reasons to be offended on behalf of others who they have decided are too stupid to realize they are being offended ) but there is nothing fabulous about them either
Standard 2 stroke practice was rollers on both ends of the con rod as it is with most hand held tools now days .

I have troubles when some one starts talking about high quality engineering but can not understand how a ball bearing can locate a crankshaft & control end float .

There is a good reason why lawn Boy was a brand that was only sold in America and not anywhere else on the planet .
But that is just me .

This link to an F Series manual on the Tractor Forum may be of some help.

I am still to see a well written service on these engines. Some of us have not even seen the insides of these engines so we are unfamiliar with assumed things the manuals leave out.

Who is it that "can't understand how a ball bearing can locate..." ? Certainly not me, I understand it just fine. The issue isn't understanding, the issue is not automatically assuming that a bearing assembly designed for lateral loads would be intentionally abused into providing thrust bearing, too.

If you are intending to provide thrust bearing, use a thrust bearing. This is obvious.

If you are intending to provide both lateral and thrust bearing, use a conical bearing. Obvious.

Jamming the balls against the races? This is obvious corner cutting and anathema to "high quality".

StarTech: I was unable to send you a message. Do you have messaging shut off?

Yes. Because I got crawled about using PMs so I turn both PMs and emails off that way I wouldn't have the perceived problems when I had only sent info that was propriety that every Tom, Dick, and Harry didn't know. Beside management acted like they were reading my private conversations and they didn't need to know what I was discussing with another member; that is why it is a private conversation.

Sorry this is the way it has to be here on this forum. I also learn to step out a thread when stupid comments are made. Some members were rather hatefully when I corrected their errors when I knew what was posted was wrong info. Calling me a smart A doesn't cut it with me especially when all I was trying to do was to help.

With this I going back to finish assembling the Super Z that redone a hydro pump and replace the engine's crankcase gasket. Just had to rest after trying to get the PTO on. Finally had to use a bottle jack as my right arm kept giving out. I messed the shoulder up last Summer falling down a flight of steps. Still have length time limits. Now I got to route the PTO cable, put on the deck belt, and then fill the oil tank and engine's crankcase. I hope the weather holds out thru Saturday.

FuzzyDriver said:

"I have troubles when some one starts talking about high quality engineering but can not understand how a ball bearing can locate a crankshaft & control end float ."​

Who is it that "can't understand how a ball bearing can locate..." ? Certainly not me, I understand it just fine. The issue isn't understanding, the issue is not automatically assuming that a bearing assembly designed for lateral loads would be intentionally abused into providing thrust bearing, too.

If you are intending to provide thrust bearing, use a thrust bearing. This is obvious.

If you are intending to provide both lateral and thrust bearing, use a conical bearing. Obvious.

Jamming the balls against the races? This is obvious corner cutting and anathema to "high quality".

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Not an unreasonable assumption when some one says " Ball bearings would not be better. Neither ball bearings, nor straight needle bearings affect end-play "
And no arguement that a tapered roller bearing would be better.

There is controlling end float and HEAVY LOAD Handleing thrust bearings / washers
There is 5/8 of SFA axial load on a vertical shaft push mower engine .
the 400,000,000 B &S sprint engines still running is testiment to that fact
In the 10 year I have been doing this for a living I am yet to find an engine failed from excessive axial wear
OTOH 2 to 3 of them go into the parts / scrap pile each year because the twist ( side load ) on the top bush has caused it to wear oval to the point it jams the pull start
Moving the air is nothing like the load of chopping the grass
Chopping the grass puts a load on the front pushing back & on the side pushing left
This is bore out by the fact that most top bushes are worn oval at the front & right
The blade exerts a load, the bottom bearing / bush acts as a fulcrum point to apply the load to the side of the top bush / bearing .
Peoples persecption of quality is usually corrupted by price & marketing
Rolls Royce is held up as being the best and is used regularly to infer quality
The RR of motorcycle, the RR of lawn mowers, the RR of pop up toasters etc etc etc
Well RR did not put an oil seal at either end of their cranks till VW took then over & fitted a modified Audi 5 engine in there
Now the oil slingers work exceptionally well but leave your car sitting on a steep slope with the engine off and you end up with 1/2 the sump contents on the ground .

"Peoples persecption[sic] of quality is usually corrupted by price & marketing"

I could "pedantic" you on that one, but I see what you mean.

Its one of the reason I like to put on my tools before purchasing them or order a trial tool. Some brands that I am familiar with I do order without question but it because quality I get and not hype. Sometimes there is no choice as a tool is an usual size or design that I need.

I right now I am researching to see if of my trusted tool suppliers can supply the 22mm deep well impact socket I need here. Local supplier don't carry it.

StarTech said:

With this I going back to finish assembling the Super Z that redone a hydro pump and replace the engine's crankcase gasket. Just had to rest after trying to get the PTO on. Finally had to use a bottle jack as my right arm kept giving out. I messed the shoulder up last Summer falling down a flight of steps. Still have length time limits. Now I got to route the PTO cable, put on the deck belt, and then fill the oil tank and engine's crankcase. I hope the weather holds out thru Saturday.

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Wow. Hope your shoulder is feeling better and you got that Super Z done.

Oh it was a challenge to get to PTO clutch on. I ended up having to use a bottle jack as assist to get it on. I just couldn't hold the clutch up long enough to align the bearings but finally got it on and the mower is back home with the customer.

FuzzyDriver said:

"Peoples persecption[sic] of quality is usually corrupted by price & marketing"

I could "pedantic" you on that one, but I see what you mean.

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Be my guess Fuzzy
I have dyslexia so spelling is not a strong suit
I gave up trying to check every word written well before internet forums were invented.
Down here post WWII the government realized how vulnerable we were to supply chain disruptions.
So they brought in big import duties along with the import replacement subsidy plan .
SO those who like to milk the government set up small factories to make shoddy copies of stuff we imported .
Thus there was born a cultural cringe that all high quality products were imported and all local made products were trash.
This is still part of the culture so it is near impossible to get any market penetration for a locally made product despite the fact that the local product is vastly superiour to what was being imported.
Victa once had 75 % of the local market, but most were branded with resellers name .
OTOH in the UK they sold for bigger money because the UK was by & large used to doing repairs on their own machines so the simplicity of the power torque appealed to them .
They sold very well in Germany because Germans appreciate good sound engineering .
Australians expected them to run forever with no maintenance so the 5 year & 10 year maintenance never got done thus they became hard to start so the owners went out & bought a Honda because the start so easy.
When I service the old piece of !!!!! sitting in the back of the shed and they see it start 1/2 through the first pull they can not believe what they are seeing.
Then when they start using it as "back up" the $ 1600 SP Honda ends up down the back of the shed , particularly if they mulch rather than catch ( Victa catchers were always too small )
The stupidity of it is Victa never thought about selling 5 year & 10 year service kits to hammer home just how cheap they were to run & maintain .
We had 5 companies that made ride ons and 8 that made walk behinds . nearly all have closed down because the locals will not buy locally made mowers despite the fact they they are so much better than anything we import.
My Greenfields Fast cut 34" cuts a acre much fasted than any other tractor style mower with decks up to 50" and can just about equal a 42" ZTR, has a service life of around 30 years and uses standard pollyester belts which usually wear out rather than break .
But they went bust last year because stupid Aussies would rather purchase the heavily advertised Husqvarna's that are pushing it to make 5 years , eat $ 100+ belts at an alarming rate , go through blades every season & because there is no overlap on the blades require double cutting to remove the unmowed strips between the blades if you let the grass get any higher than 6" and we are getting near 10" of growth a week right now .

I did work on those lawnboys in 70s and 80s.I know exactly what youi talking about.I fixed them by putting spacer that friend made for me out of some oil lite material.

bogdaN said:

I did work on those lawnboys in 70s and 80s.I know exactly what youi talking about.I fixed them by putting spacer that friend made for me out of some oil lite material.

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There are so many posts in this thread that I don't know for sure which you are replying to, but it sounds very interesting. Could you give some more info?

I was refer to first post.Orignal engine did not come with that trust bearing and washer.Problem was like you describe that fly wheel was catching starter gear.At first i was just putting steal spacer than made improvement and switch to that special material.But this mowers come back for tune up and never had problem with fly wheel dragging on that plastic gear.

Ah! You were referring to post #7 (also mine):


My temporary fixes have been to periodically add thin spacers between the starter and shroud screws and the shroud and shroud-base screws. I'm up to about 3/16" now to stop the pinging. Once I get this mower finished, my daily-driver is coming in and getting a serious teardown to see what's going on. I hate doing it because it's still running great (for 30+ years), but the ping....ting....ting..ping.ting is very annoying. At least now I understand that thrust (i.e., crankshaft endplay) is controlled only by the crankcase cover, and not the crankcase.

Here's a sneak-peak at the mower I'm building. It's nearly done, just needs me to put on the flywheel, CDI, carburetor (Walbro), and shroud.: