Scuffing a Yanmar YSE 12 clutch?

[Scubaseas]

Originally Posted by Will10MNT

I lost foward power from the transmission some time ago, its a 1974 yanmar yse 12, and took apart the gear box to try and 'deglaze' the foward clutch plate. Ive finally got the thing apart after a lot of confusion, but now im not positively sure what part here I should be cleaning with what, sanding, or adding any fine grinding paste to, or what damage is really present on any of the plates. Any help is greatly appreciated, happy new years all.

I've seen good and it doesn't look anything like two of your pictures. Deglazing won't help you here.

If you want to try it brakekleen first then lightly sand with h400 grit.

[Boatyarddog]

Originally Posted by Will10MNT

I lost foward power from the transmission some time ago, its a 1974 yanmar yse 12, and took apart the gear box to try and 'deglaze' the foward clutch plate. Ive finally got the thing apart after a lot of confusion, but now im not positively sure what part here I should be cleaning with what, sanding, or adding any fine grinding paste to, or what damage is really present on any of the plates. Any help is greatly appreciated, happy new years all.

Those lines radiating out from the friction disc look worn.
That indicates a worn disc.
As this is a clutch, the Pressure plate incorporates a diaphragm spring or actual springs to pressure the friction disc to the flywheel plate.
It's probably lost its spring pressure and is allowing it to slip, thus wearing the F. Disc.
Replace the disc, sand the rust off the flywheel plate, replace the Pressure plate.
Reinstall.
SV Cloud Duster

[Boatyarddog]

[QUOTE=Will10MNT;3311443]I lost foward power from the transmission some time ago, its a 1974 yanmar yse 12, and took apart the gear box to try and 'deglaze' the foward clutch plate. Ive finally got the thing apart after a lot of confusion, but now im not positively sure what part here I should be cleaning with what, sanding, or adding any fine grinding paste to, or what damage is really present on any of the plates. Any help is greatly appreciated, happy new year

https://www.google.com/url?sa=t&sour...D1novNGz9plHNC

[Boatyarddog]

https://www.google.com/url?sa=t&sour...D1novNGz9plHNC
Seems to have what you need here

[Boatyarddog]

That clutchpack has two friction discs, hopefully I've sent a good url.
Pm me if you need to

[Compass790]

Originally Posted by Scubaseas

I've seen good and it doesn't look anything like two of your pictures. Deglazing won't help you here.

If you want to try it brakekleen first then lightly sand with h400 grit.

Yep +1 for this.
I think his disk is worn out & needs to be replaced but there is no measurement in the YSE manual for original thickness that I can find. Just says max 2mm wear. Having nearly no lines radiating out suggests its worn out.
Wotname had a good idea compare fwd disc thickness to reverse disc for a start.

The rusty look is a bad sign as well.
On the + side the gearbox is strongly built.

[Ken Fry]

I've deglazed hundreds of clutch plates in a motorcycle context, and have deglazed the flywheel and pressure plate for automotive clutches. (Usually the friction plate is cheap enough to simply replace even if the customer is on a very low budget.) But in either case, the glaze would not prevent the clutch from engaging, it would only affect the degree of chatter upon engagement (between just starting to engage and fully coupled up).

Maybe some general theory will help you:

In automotive and motorcycle applications, clutch plates get so thin that the friction material is almost entirely gone, and the clutch or brake still functions, it just functions poorly. (In various motorcycle applications (and some automotive automatic transmissions) the wet clutch plates are entirely steel -- no "friction material" (organic sintered or mineral), per se. In a marine application, the clutch could be slipping (possibly destructively so) and the damage would not be as obvious, because slippage is harder to detect. Looks like these clutches have been slipping a lot.

When a standard old dry plate clutch on an old car starts to slip, it is because the worn clutch plate takes up less space. Therefore, spring tension (the springs now extended too much) becomes too low to supply the force required to prevent slipping. Something of that nature may be happening with your clutch: whatever is suppose to be applying pressure is not applying enough.

In an old car, replacing the "clutch and pressure plate" meant replacing the driven plate (the one with both sides faced with riveted or bonded friction material) and replacing the assembly that applies pressure (which included the springs, and a very thick steel plate).

I have not had to fool with marine clutches, but in all the motorcycle, car, and industrial clutches I've fooled with, having the manufacturer's specs on wear limits is nearly essential -- and the spec has to be for precisely the model of transmission in question.

But in my experience, glazing (or polishing) does not stop a clutch from working. Clutch surfaces can look quite well-polished not long after break-in. Your surfaces are not what is traditionally called "glazed".

To me, your clutch surfaces look really awful, like those on a wet clutch that has been run dry. I imagine that the force holding the plates together is (and has been) too low. One plate seems to have its grooves entirely worn away. Someone who knows your make and model of transmission could elucidate.

I think someone mentioned comparing forward and reverse plate thickness, a good suggestion. However, I'd guess that they are shot too. Nothing in your pictures looks in the ballpark of being functional.

Faced with stuff like this on classic cars, I have re-machined the surfaces, relined, etc. That might be horribly expensive relative to your ships value.

There are plenty of companies that can reface clutch plates, BTW. If your discs are still available, then you appear to need at least both forward and reverse discs. If this is supposed to be a dry clutch, then you have crankshaft sealing issues.

[Wotname]

FWIW - The YSE transmission uses a constant mesh transmission and a single plate wet clutch (one for forward and another for reverse).

[Compass790]

Good post Ken Fry,
Should help the OP's understanding quite a bit
Interesting thinking it had run dry, thought water was the cause of the rusty look but could be either.


I suspect, but don't know, OP will be forced to reline his friction discs as parts might be NLA. Also price for new ones, if available, may make relining look attractive.

Another option would be to get another used gearbox or whole motor & box.
Usually the engine dies before the clutch/ gearbox give trouble & they can be picked up cheaply.

If the crankshaft seal leaks they leak engine oil into the gearbox/clutch assembly & that is noticeable as the oil in the gearbox then becomes dirty.

[Ken Fry]

Originally Posted by Scubaseas

I've seen good and it doesn't look anything like two of your pictures.

You could write country music!

Yes, the discs are shot. I've seen dry clutches where the lining is worn down to the rivets, and pretty well scored pressure plates and flywheels, but these ones are a lot worse than I've seen for wet clutches. Wet clutches that are serviceable have very smooth, flat, often shiny surfaces. If they are gnarly looking, they are well beyond being useful.

The pressure plate could probably be trued up with a some figure 8 sanding on a flat surface.

At least the bearings are all common numbers. I can't see what keeps the oil in.

[Ken Fry]

Originally Posted by Ken Fry

The pressure plate could probably be trued up with a some figure 8 sanding on a flat surface.

Here, let me start arguing with myself:

I looked a little closer at the photo of the pressure plate. It cannot be trued up to something like what would be an actual spec... if the darn manufacturer would give one. An ordinary spec for a piece like this would be flat within .001" at manufacture, and flat within .020" at the wear limit. I would guess that the lip on the unworn edge of the plate is about .030" and an ordinary manufacturer would say "shot". An ordinary manufacturer would (and should) make these details very easy to find. Hardly any manufacturer would specify the wear limit on the friction discs as X amount of wear (as Yanmar does here: 2mm) because how is someone in the field supposed to know what the thickness of a new part is???!!! Yanmar is saying, "screw you, if you don't work in a shop with a full compliment of new parts, then you shouldn't be working on this transmission."

If this were the sort of clutch with big coil springs or a big diaphragm spring supplying the force, then the untrue pressure plate would cause the new friction plates to wear-in to match the pressure plate, and the result might work ok. This clutch is not like that, however. That's one reason why, when it should be "engaged," it transfers near-zero torque. It looks like the geometry between the parts is more critical in this design. So new discs against the old pressure plate would, at first, have near zero contact area, meaning some very hot hot spots as things wear in, and then increasingly lower pressure as they do so.

It is not impossible that this wear-in (of new discs to old pressure plate) would work. It could end up working fine. (Maybe.) At very least, the outer edges of the new discs should be beveled (before installation) so that they do not contact the unworn part of the pressure plate.

The yse 12 is rated for 12 hp at 3200 rpm, so engine torque at that rpm is about 20 lb-ft. This would be either 40 or 60 lb-ft at the prop shaft (with 2:1 or 3:1 gears). So you would want the assembled gearbox to transmit at least double that, say 120 lb-ft, to have a little margin for safety. A torque wrench can be used to make this check, (if used on a nut that is big enough). I'd do that before installing this in the boat, if I attempted a rebuild. (Locked flywheel, etc.)

BTW, I am using "pressure plate" and "friction disc" in ways that any mechanic would understand. The Yanmar manual has their own strange terminology for parts. If the manual were produced in 1920, I suppose there would be some excuse, but by 1968 at least, Honda manuals were excellent, and were read by many native english speakers before being published. It is not that difficult to put out a good manual.

Stunningly bad manuals have accompanying pictures in which the terminology is different in the steps vs the picture description.

(Rant
- Step 9: "Remove one holding friction disc." The drawing does not have a "holding friction disc".
- Part #9 (which virtually any English speaker would call a "friction disc") is called a "friction disc keeper"
- Part #6, the pressure plate, is called a "friction disc."
- Step 4 should be inserted before the existing step 4, (which then becomes step 5). Step 4: Position the housing assembly so that the bores into which the positioning claws fit are aimed as follows: One toward the V berth. One toward the head. One toward the aft quarter berth. Then, when you execute the next step, you will know where to look for the flying parts. Refer to drawing for orientation of aforementioned bores.
- Positioning claw? Oh, that's the "friction disc claw" in the drawing. Clearly not a soul tried out the instructions to see if the drawing and the steps match. (The "claw" is probably what many people would call a "detent plunger" )

I don't envy the OP, and can fully understand how he could be confused when taking the unit apart. The manual is just awful.

Not shown in the OP's post are the surfaces inside the housings (A and B) , which also need to be flat, smooth and close to where they were (axially) when manufactured. It is very unlikely, given the condition of the other pieces, that this will be the case.

Sad to say, it is probably time for a new unit, unless the OP is willing to piece together as much as he can and try it out. Given enough money, with some metal spray and machining, this could be made like new -- but I cannot imagine that making any sense at all. For a 1930 Bentley? Maybe so.

With a used unit in good condition, a minor rebuild (new friction discs) would be prudent. The sort of damage this clutch has can be avoided with occasional replacement of friction discs, maintenance of oil levels, etc.

[Wotname]

Originally Posted by Ken Fry

Here, let me start arguing with myself:

I looked a little closer at the photo of the pressure plate. It cannot be trued up to something like what would be an actual spec... if the darn manufacturer would give one. An ordinary spec for a piece like this would be flat within .001" at manufacture, and flat within .020" at the wear limit. I would guess that the lip on the unworn edge of the plate is about .030" and an ordinary manufacturer would say "shot". An ordinary manufacturer would (and should) make these details very easy to find. Hardly any manufacturer would specify the wear limit on the friction discs as X amount of wear (as Yanmar does here: 2mm) because how is someone in the field supposed to know what the thickness of a new part is???!!! Yanmar is saying, "screw you, if you don't work in a shop with a full compliment of new parts, then you shouldn't be working on this transmission."

If this were the sort of clutch with big coil springs or a big diaphragm spring supplying the force, then the untrue pressure plate would cause the new friction plates to wear-in to match the pressure plate, and the result might work ok. This clutch is not like that, however. That's one reason why, when it should be "engaged," it transfers near-zero torque. It looks like the geometry between the parts is more critical in this design. So new discs against the old pressure plate would, at first, have near zero contact area, meaning some very hot hot spots as things wear in, and then increasingly lower pressure as they do so.

It is not impossible that this wear-in (of new discs to old pressure plate) would work. It could end up working fine. (Maybe.) At very least, the outer edges of the new discs should be beveled (before installation) so that they do not contact the unworn part of the pressure plate.

The yse 12 is rated for 12 hp at 3200 rpm, so engine torque at that rpm is about 20 lb-ft. This would be either 40 or 60 lb-ft at the prop shaft (with 2:1 or 3:1 gears). So you would want the assembled gearbox to transmit at least double that, say 120 lb-ft, to have a little margin for safety. A torque wrench can be used to make this check, (if used on a nut that is big enough). I'd do that before installing this in the boat, if I attempted a rebuild. (Locked flywheel, etc.)

BTW, I am using "pressure plate" and "friction disc" in ways that any mechanic would understand. The Yanmar manual has their own strange terminology for parts. If the manual were produced in 1920, I suppose there would be some excuse, but by 1968 at least, Honda manuals were excellent, and were read by many native english speakers before being published. It is not that difficult to put out a good manual.

Stunningly bad manuals have accompanying pictures in which the terminology is different in the steps vs the picture description.

(Rant
- Step 9: "Remove one holding friction disc." The drawing does not have a "holding friction disc".
- Part #9 (which virtually any English speaker would call a "friction disc") is called a "friction disc keeper"
- Part #6, the pressure plate, is called a "friction disc."
- Step 4 should be inserted before the existing step 4, (which then becomes step 5). Step 4: Position the housing assembly so that the bores into which the positioning claws fit are aimed as follows: One toward the V berth. One toward the head. One toward the aft quarter berth. Then, when you execute the next step, you will know where to look for the flying parts. Refer to drawing for orientation of aforementioned bores.
- Positioning claw? Oh, that's the "friction disc claw" in the drawing. Clearly not a soul tried out the instructions to see if the drawing and the steps match. (The "claw" is probably what many people would call a "detent plunger" )

I don't envy the OP, and can fully understand how he could be confused when taking the unit apart. The manual is just awful.

Not shown in the OP's post are the surfaces inside the housings (A and B) , which also need to be flat, smooth and close to where they were (axially) when manufactured. It is very unlikely, given the condition of the other pieces, that this will be the case.

Sad to say, it is probably time for a new unit, unless the OP is willing to piece together as much as he can and try it out. Given enough money, with some metal spray and machining, this could be made like new -- but I cannot imagine that making any sense at all. For a 1930 Bentley? Maybe so.

With a used unit in good condition, a minor rebuild (new friction discs) would be prudent. The sort of damage this clutch has can be avoided with occasional replacement of friction discs, maintenance of oil levels, etc.

Excellent post Ken Fry and I concur about the manual limitations.

For the OP, I have found using both the YSM and the YSE manuals very helpful. The YSM manual is better written (but not perfect) and it fills in many of the 'gaps' of the YSE manual. The engines are very similar and I guess more than 90-95% of the parts are the same. The few differences become obvious once the manuals are read alongside of each other.

FWIW, I would say with some confidence, the clutch assembly is the same or almost the same. Mind you - I could be wrong . I haven't seen a YSM clutch up close and I haven't read the two manuals this morning...

Do let us know what eventuates with your clutch problem.

[Compass790]

Glad you argued with yourself Ken Fry,
I too enjoyed your post. .
Pressure plate should be 18mm & min thickness 17.8mm if the same as YSM. Yes, as previously stated, he'd probably be better off with buying another used gearbox as they are pretty bulletproof if kept supplied with oil & not submerged. Our 1980 8hp one with indeterminate hours shows little wear but his problem will be finding one. I'm pretty sure its the same gearbox for the 8hp as the 12 which widens his search range somewhat.
He would be very unlucky to find one in as poor condition as his is.

[Ken Fry]

Originally Posted by Compass790

Pressure plate should be 18mm & min thickness 17.8mm if the same as YSM.

In "real" units (as the queen intends), that's just .008" of wear, and that little lip is certainly more than that... if my laser eyes still work.

(Many many years ago, I taught motorcycle mechanics, and could, most of the time, eye up a points gap and say, to the student "looks a little tight" and be right surprisingly often. It baffled the students -- and me to some extent. I could definitely get spark pugs plenty close enough to run fine, but not as close to spec as with points, which were 90% of the time set at .016". But that was a long time ago, and the pieces were real things right in front of me, rather than some digital representation.)

(More old fart ramble: the adjuster screw for tappets can work like a micrometer, if you practice a little. So I could fool students into thinking I had magic powers by setting tappets without a feeler gauge (snug, and then back off 45 degrees, etc.))

(Yet more... drifting even further off topic: in the tire industry there are calender rolls, a couple feet in diameter and 8-10 feet long. There is a guy that goes around the country and gets the rolls straight and true to within a few .0001's of an inch, hand hand lapping and polishing. Magic. )

[Compass790]

Originally Posted by Ken Fry

In "real" units (as the queen intends), that's just .008" of wear, and that little lip is certainly more than that... if my laser eyes still work.

(Many many years ago, I taught motorcycle mechanics, and could, most of the time, eye up a points gap and say, to the student "looks a little tight" and be right surprisingly often. It baffled the students -- and me to some extent. I could definitely get spark pugs plenty close enough to run fine, but not as close to spec as with points, which were 90% of the time set at .016". But that was a long time ago, and the pieces were real things right in front of me, rather than some digital representation.)

(More old fart ramble: the adjuster screw for tappets can work like a micrometer, if you practice a little. So I could fool students into thinking I had magic powers by setting tappets without a feeler gauge (snug, and then back off 45 degrees, etc.))

(Yet more... drifting even further off topic: in the tire industry there are calender rolls, a couple feet in diameter and 8-10 feet long. There is a guy that goes around the country and gets the rolls straight and true to within a few .0001's of an inch, hand hand lapping and polishing. Magic. )

Enjoyed yr ramblings, yes its amazing how good an eye some people develop with practice.
To continue the thread drift a large American rifle barrel maker used v-blocks & a hammer to straighten their barrels after rifling. Just a man looking down the barrel & the play of light was used to determine if it was straight. This wasnt that long ago.
Yanmar gives a backing off of the rocker arm adjusting screw by one nut flat as a setting for tappets in the ysm8 manual.
Like the tri you built that you call a cat, bet its a goer.



Wonder how the OP is getting on?