School me on the mechanical PTO
 

OK.... 123 is running pretty well, if still not stopping well, but we're going to live with that, since I don't want to make this my lifes work.

On to the Last Big Thing keeping me from using this bad boy. The PTO.

I've never used this particular PTO, (it was on the replacement engine) but I'm not sure I understand the operation. I've never had one apart though I've had full sized clutch/pressure plate/flywheel assemblies apart many times, so I conceptually know how they work.

Engine OFF:

With no pressure on the PTO button (via the PTO lever) the crankshaft of the engine and the pulley on the PTO are locked and turn as one (well, there's a bit of slop I'll attribute to the wear in the woodruff key or the crank ... I can move it about 5 degrees )

With pressure ON the PTO button I can move the pulley independent of the basket/crank, as I would expect.

That all seems right.

Now , ENGINE ON:

When I apply pressure to the PTO button via the PTO arm, and then wedge a 2x4 against the PTO pulley ( I have no belts / deck on this yet and I was trying to simulate the load of an actual deck) I cannot stop the PTO pulley.

I would think that the running behavior should match the static, in that the pulley should be stoppable when I have the PTO button pressed in? What am I overlooking ? Why shouldn't I be able to stop it since the clutch button is depressed?

( be easy on me, I'm an electronics engineer) :-) Button is adjusted correctly

Bad PTO bearing ??

:bigthink:

Keep in mind the PTO for the 123 does not have a brake. There's not much stopping leverage pressing on the button without an implement to drag it down.

Otherwise, make sure the bearing works freely and is lubed.

Thanks guys.

Since it's really easy to turn the PTO pulley in relation to the crank (it's not spin free, but I can rotate it easily with thumb and 1 other finger) with the engine off and the PTO depressed, I'd have thought that it would be simple to stop it in the same condition with the engine running, but that's not the case (I was pushing on the pulley pretty good with the end of a 2x4). Doesn't make sense to me, but again, I'm not a PTO expert.

I don't mind pulling the grill and trying to get the PTO off but I'm wary of the of broken/stripped set screws. I've got 'em soaking in Kroil.

If the 3 springs aren’t adjusted properly the PTO won’t disengage all the way.

If the engagement lever is adjusted properly , then possibly the clutch wasn't adjusted properly via the three screws and assembly gauge ? Try a rubber tarp strap hooked to the frame and up over the pulley as a belt would go and see what happens ? it should stop turning with engine running with a little resistance holding it if everything is right !:beerchug:

Well, that's what I thought too. I wedged in a 2x4 between the frame and the pulley on the exhaust port size, and I had it tight enough for the pulley to start the wood charring from the friction.


If I can get the double set screws out, I'll check it, but darned if I can figure out how it is it's free with the engine off (I can easily rotate the basket in regards the PTO itself so the holes line up for the set screw) .

Strange!

Yea , something's not quite right ! The PTO on my 109 will pretty much stay put without a belt on it. It will be interesting what you find! Blow those set screw holes out with air if you can, and they should come out if you have soaked them. Unless, someone before has them boogered them up!

:beerchug:

I have seen PTO's that were working perfectly fine, and then from sitting in a neglected state wouldn't even dis-engage because rust and dirt crept in between the plates and disc.
Even though you have the "button to button" gap adjusted correctly, you still need to develop an air gap between both plates and thd disc when the button is pushed in.
I think you need to get it off and apart, cleaned up, and adjusted correctly, and you will be OK.

Be sure when you do all that you check for a broken or missing snap ring on the pulley.

I got all three (!) set screws out without a lot of drama. Just a little patience, Kroil, and time and a couple taps each, with a long skinny punch seated at the base, of the hex screws. I'm going to shoot some more solvent down those holes and let'em soak a bit before trying to remove the assembly.

There are 6 screws in my experience. 3 to hold the clutch on the bearing, and 3 more to keep them from backing out.

:IH Trusted Hand:

I'm not the first one who's been working on this over the years. There's a lot of randomness I've encountered.... apparently some previous owner found them to be optional parts. We've got short set screws and long set screws....

The longer 3 with pointed ends are at the bottom of hole against the bearing, 3 shorter ones without pointed ends are at the top to hold the others from backing out ! :beerchug:

Well, it all came apart fine, and I don't see anything wrong other than these two items:

• One of the adjustment arms was loose. I mean, there was a jam nut on their as it should be, but the whole bolt/jam nut assembly (and its corresponding "pressure plate" finger was completely loose. I wonder if it was due to observation 2
• There was a small nut (same size as the jam nuts) rattling around in there that fell out when I removed the PTO. I wonder if this was somehow jammed in the clutch assembly when the previous owner was inside , which led to the loose bolt? A mystery lost in time. All of the adjustment bolts had two nuts on them, so this one hadn't fallen off.

While not being an expert in anything, 40 yrs of shade tree mechanics has taught me that extra hardware falling out of an assembly is rarely a good sign.


Anyway, I don't have one of those nifty adjustment tools, but I don't see anything wrong with this other than it had some insect corpse's in it, random loose hardware and loose adjustment bolts. The bearing seems fine... not loose in its race or emitting any grittiness or looseness.


I think I'll clean it all up and put it back together and see what happens when/if it's adjusted correctly.


Pro Tip: An old driveshaft makes a nifty PTO removal tool. The flange where the rag joint used to attach goes in the pulley V, and you hammer on the small end. I'm really glad I saved this when I got the new one from Jeff . Patience, Kroil and a bunch of taps around the rim rotating the crank after every 2-3 taps and off it came. The offset of the rag joint flange is perfect at allowing you to tap and provide a force that's almost parallel to the crank.

Hmmm......

The nut you found is prolly from the PTO locking collar as some use one. Need a gauge. the only way to do it correctly...

Ah that's too bad, was hoping I could make something.

Anyone know where I can buy one (without buying a clutch rebuild kit?)

Make one using the drawing out of something stiff. :HeeHee:

Well, I may try that , but I found a gauge from one of our friendly online forum sponsors (I think) for all of $4, so that's a deal. I have to order some of those pointy set screws anyway.


I need to go buy some nuts too .. .. the ones on this thing are all buggered up.


I'll look at that shaft collar. You might be right about the source of that extra nut rattling around in there. :bigthink:
(edit: nope... fits neither the locking collar screw or the clutch bolts. )



Thanks Lew!

Hopefully by now you have studied this in the tech library....

https://www.onlycubcadets.net/forum/showthread.php?t=9

More...
 

I have indeed studied that... thanks (I've not seen the one with the brake!) . Mine is the single spring job.

Update:


I found another PTO that I forgot I ordered ...oh, 10 yrs ago. It was sold as rebuilt (and looks to be). Long story short: I put it on and have the same result. The PTO clutch works as advertised when the engine is OFF but with the engine running, I cannot stop the pulley with the 2x4.

User ATHOMAS mentioned putting a strap around it when off and trying to start the engine. While I'm not Mister Safety, I may try this with great caution as I'm thinking that maybe what I'm seeing (other than the new clutch button being consumed ) might be that once the engine has started, there's so much rotational mass that it's unlikely to stop?

The downside is that I could take my head off when the bungee strap explodes....

It's unlikely that BOTH PTO's are bad in the same way, so there must be something else. Bearing is possible, but it sure feels OK . It doesn't spin free but feels like it's got grease inside and there's no wobble or grittiness.

Update: Applied bungee in such a way to freeze the pulley in place , then put the clutch lever so that the button was depressed. Took spark plug cable off and cranked it. Pulley stayed in place, and no barnyard noises. Put spark plug cable back on, started engine, and pulley stayed in place and PTO button(s) were stationary of course

So... with no load on the PTO pulley, there's so much rotational mass on that pulley that you'll set a 2x4 on fire before you'll stop it once the engine is running . ATHOMAS, you sir, win the Internet!

I'll reassemble the original PTO once the gauge gets here ($4) with the shiny new jam nuts

Got the gauge, cleaned and painted, made sure Lew's snap ring was in there and I've got a new spare for the Cub tub.