Engine Thrust Bearing

[FuzzyDriver]

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!

 

[FuzzyDriver]

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!

 

[StarTech]

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.

 

[FuzzyDriver]

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.

 

[Rivets]

Which engine model are you referring to?

 

[StarTech]

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.

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.

 

[Rivets]

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

 

[FuzzyDriver]

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.

 

[FuzzyDriver]

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). : ^ )

 

[Rivets]

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