PTO Thrust Bearings

[tarcoleo 119]

Why do some Kohler engines (on C-81) not require a thrust bearing to support

the PTO lateral forces while Briggs engines (on C-111) do provide a special

bearing for thrust?

The reason to ask is that I just bought a C-81 and am in the process of fitting

a 13 hp Chinese Honda to the tractor. Bottom line: do I need a separate

thrust bearing or is the Honda ball bearing equal to the Kohler engine bearing?

My suspicion is that the Honda bearing won't need a dedicated thruster.

Tom in RI (swamp yankee)

[TT-(Moderator) 1,127]

The Briggs engine on the C-111 is what as known as a "plain bearing" block. The crankshaft spins in the aluminum block and side cover and does not have ball or roller bearings. (same as a push mower style engine)

Due to the side load of the manual PTO, a thrust bearing was used to absorb the load at the drive pulley/side case area instead of at the flywheel side crankshaft main journal. Without the thrust bearing, the crankshaft on the aluminum Briggs engines (horizontal shaft) can actually seize in the flywheel side of the block. (from lack of oil and related heat/friction)

Most engines with ball bearing mains on the crankshaft should be OK, but the tapered roller bearings like used on the HH Tecumsehs are actually the best at absorbing the side load of the PTO clutch.

[tarcoleo 119]

Much appreciated Terry. My first installation of a Honda in a C-111 used

the thrust bearing that came with the junked Briggs. That was 16 years ago

and the thing has performed flawlessly. It was so much fun, I picked up

a C-81 and am doing it again with the Chinese 13 hp Honda. But no free

thrust bearing. Anyway, a thrustbearing-equipped pto may come my way

in which case I will use it. But as you point out, it may not be needed.

Thanks again,

Tom

PS- Near as I can tell, the 13 hp sold by Harbor Freight for $300 IS a Honda!

[pfrederi 17,143]

You cannot be sure about the crank bearings just based on manufacturer. Some Kohler KT17s had ball bearing mains (those for WH for example)...but KT17s used by John Deere and others used plain bushings for the mains. (I used a JD KT17 to repower my C-175 and had to convert it to an electric PTO clutch)

JDs and Cubs that used a fore and aft engine mounting (driving the unit off the flywheel end of the crank and the electric PTO off the other end didn't need to worry about end thrust and bushings are cheaper than ball bearing.

When Kohler came out with series II KT series they no longer used ball bearings. They used bushings but added a flat needle thrust bearing on the PTO end to take the load.

[rick 215]

The Briggs&Stratton specification 252417-0198-01 engine used in the

C111 is equipped with a ball bearing supported crankshaft, on the magneto

(flywheel) end only.

[pfrederi 17,143]

I would think that so long as there was at least one ball bearing you would be OK. Afdter all Kohler only put one thrust bearing in the Series II KTs. WH used only one external ball bearing when thy had to use B&S Motors with no ball bearings....

[tarcoleo 119]

Paul in Pa-

In the case of the Honda 13, there are ball bearings at both ends of

the crank shaft, so I may be ok as you suggest.

You indicate that you have re-equipped your C-81 with a Kohler Magnum

engine. Did you provide an additional thrust bearing in that pto assembly?

Tom in RI

[pfrederi 17,143]

The magnum 12 I got had 2 ball bearings so I didn't need to add anything.

[pfrederi 17,143]

The Briggs&Stratton specification 252417-0198-01 engine used in the

C111 is equipped with a ball bearing supported crankshaft, on the magneto

(flywheel) end only.

Rick: I looked up the C-111. Wheel Horse added a thrust plate 108074 and a thrust bearing 106495 behind the PTO for that motor.

I guess they felt 2 bearings were needed to handle the end thrust......

[rick 215]

My plate and thrust bearing are laying on the bench, the cylinder and crankshaft are

at the machine shop......I was wondering how preload, if any, was set up on the PTO

bearing, and just in time here comes the new WH documentation website. In the list of service bulletins lies the answer!

[PeacemakerJack 10,670]

Dredging up a SUPER OLD TOPIC but rather than start a new thread...

I picked up a C-125 retrofitted with a Kohler M18 with reportedly less than a dozen hours on it,  It sure looks good and seems to run good.  However, I'm curious about the above mentioned thrust bearing issue because of the side loading PTO.  This motor isn't a wheel horse spec engine. 

 

Spec number: 24500

Displacement: 691

Serial Number: 2430405996

 

Before I transplant it into JackRabbit, I want to make sure that it will provide Caleb with years of trouble free use... 

[19richie66 16,936]

Magnum 18 should be the same as the one in jackrabbit now. I can’t see why it wouldn’t have the ability to carry the pto side load. I believe all magnum twins have the same basic internals.

[gwest_ca-(File Mod) 10,490]

Here is the parts list. See if there was any other option. Click on the picture.

Garry

[PeacemakerJack 10,670]

Thanks Garry—

 

now I’m really scratching my head...why would WH request different specs for the 418-C versus the 418-A of the same model year?  Is there a way to know what the changes were?

[19richie66 16,936]

Only thing I see different with caleb’s engine and all the other 418’s I have seen is his has a black air cleaner assembly where as all the 418-A’s have the chrome air cleaner. Other than that, they are identical.

[pfrederi 17,143]

Not all magnums had thrust bearings...actually only a very few do.  Your spec # 24500 is crankcase variant 400 it does NOT have thrust bearings.  In the picture item 24/25/26 are the thrust bearings.  as you can see only 5 variants had them.

 

That little flange on item 23 is the only thing to handle end loading if you do not have thrust bearings.  

Doubt it would last long that is why WH paid extra for the thrust bearing version

 

You could always get an electric PTO from and Electro12

 

Edited July 18, 2018 by pfrederi

[19richie66 16,936]

What about a 24510? What does that have?

[PeacemakerJack 10,670]

Wow!  Thanks @pfrederi for your input.  I downloaded and printed the whole parts manual that Garry uploaded.  I was shocked at the differences between the WH spec'd motors and the one that I picked up.  I'll have to think long and hard about what to do with it.  I suppose that one would have to split the cases to install the thrust bearing and washers, and there might not even be a provision for them in the 24500 case.  Lots to think about...

[PeacemakerJack 10,670]

According to the chart from the download above, spec numbers 24510 and 24536 found in the 418-A and 418-C respectively.  Those both have a crankcase number of 118.  That of course is listed on the above picture of the chart indicating that both engines were spec’d with the thrust washers and bearing.  Thanks for the clarification—should’ve researched the Spec Number before making the purchase.  

 

Looks like an 18hp Magnum with ultra low hours will be available here in the area soon for applications where side loading won’t occur...

[pfrederi 17,143]

9 hours ago, PeacemakerJack said:

According to the chart from the download above, spec numbers 24510 and 24536 found in the 418-A and 418-C respectively.  Those both have a crankcase number of 118.  That of course is listed on the above picture of the chart indicating that both engines were spec’d with the thrust washers and bearing.  Thanks for the clarification—should’ve researched the Spec Number before making the purchase.  

 

Looks like an 18hp Magnum with ultra low hours will be available here in the area soon for applications where side loading won’t occur...

 

 

Trying t retrofit the thrust bearings may not be possible.  They had to make room for them.  may be in the crankcase itself in which case you would have to change that... also they may have machined the crank shaft to make room.  Only one spec # besides the 2 WH ones uses the Variant 114 Crankshaft....

 

 

Why not consider an Electric PTO???....No side loading with that.

Edited July 19, 2018 by pfrederi

[PeacemakerJack 10,670]

It is a thought for sure.  It would require me to locate a WH “Correct” electric PTO, then adapt the electric system to accommodate (wiring, switch, PTO safety switch, etc).  I’m not sure if that would be easier than just selling this engine to someone else whose application it would be suited to, and working on JackRabbit’s current engine in hopes of solving its “gremlins”—not charging, governor operation, etc.  I thought I was “pressing the easy button” by picking this motor/tractor up but not checking the spec number first was my mistake.  Live and learn.  Thanks again for all who weighed in on this...it was very informative.