Help Please, John Deere EM PTO clutch for mower deck

[Willabe]

I have an old JD rider mower, STX38 - yellow deck. I bought 4,5 years ago for $700.00 and it's worked fine up until the end of the cutting season last year when it started to not cut as well as before, even with sharpened blades.

So I just changed the air filter, spark plug and in line gas filter. I also just re-sharpened the blades on it.

It runs fine if the mower blades are disengaged, but when I engage the mower blades it bogs down to almost a crawl and wont cut worth a darn.

Turns out it has an electromagnetic PTO (Warner) clutch for the power take off from the engine to the mower deck blades.

How does this type of clutch work?

Anything I need to know about this before I change it? JD wants $130.00 for it, not too bad. I don't think there's any adjustments on it?

Looks like to drop the mower deck you just pull 4 cotter pins and take the belts off and slide the deck out from under the rider mower?

Well I guess it can be adjusted, because I just found this on how to adjust the PTO (Power Take Off) clutch on a JD;

http://www.ehow.com/how_8079519_adjust-pto-clutch-john-deere.html

Can these types of clutches burn out the clutch material until there's no adjustment left? I did read the 12v coil can burn up, but the blades are still turning when I engage the PTO switch, so I think the coil is still good. I guess I could test the coil for resistance/continuity?  


                                           Thanks,    Brad            

[Ritchie200]

Brad,

Just saw this.  When the clutch wears, it will slip.  So if you are cutting, the grass will look like crap but the engine will not bog down.  The fact that your engine bogs almost sounds like one or more of your deck spindles have bit the dust.  Do all the blades move freely?  If so, maybe the clutch is gone, locking on something non-moving?  Hey, 130 bucks for a genuine JD part is unheard of!!!!  Even cheap MTD clutches are north of 200.

Jim

[Willabe]

Hi Jim,

Yeah the blades seem to spin freely. I checked that when I took them off to sharpen them.    

When I was in HS I changed the clutch on a Dodge 3 on the tree van my dad gave me, came out fine. So I understand at least some of what's going on with a clutch. I was in my late teens and thin, so it was pretty easy back then to crawl around under the van in my parents drive way to fix it.                

The fact that your engine bogs almost sounds like one or more of your deck spindles have bit the dust.  Do all the blades move freely?  If so, maybe the clutch is gone, locking on something non-moving?

I'll know more when I take it out and have the belt free from the tension keeper pulley. I was wondering if it's sliping _or_ binding for the same reason you've brought up about the engine bogging down _only_ when the blades are engaged, ie with a load applied? I'll check the deck spindles/bearings for wear and tear and/or stiffness. I really didn't want to lay down on the ground next to the mower deck while the blades were spinning to see if I could see any problems.              

I did notice that the belt was pretty warm to the touch, but not smoking or any smell of rubber cooking and I could put my hand on it without having to let it go because it was too hot. And the tension pulleys swing arm looks like it's bending down and tipping the pulley on an angle, maybe 4-5 degrees or so?

I should be able to work on it in the next day or 2 and will post back what I find.

Thanks for the info and checking on me Jim.    


                              Brad      

[PRR]

This clutch is more like a car air-conditioner clutch than a 3-on-tree clutch. The pulley spins free until electromagnet sucks it against the shaft-plate. (Backward from car to tractor: car belt spins all the time, A/C only on demand; mower engine spins all the time and belt only on demand... the clutch doesn't care.)

A slippy belt will cut awful, but turn easy.

I agree: chugging when engaged (and no compost-clump under the deck) is bad spindles. Drop the deck, pull it out (or drive off), tip it up. Get the belt dead-slack, zero drag on pulleys. Modern mowers may need a blade-brake defeated. Used spindles should turn about as free as a bicycle wheel. 6 years is not too soon for the factory grease to have gunked-up, especially if you did not know spindles have grease fittings.

Hey... check that blade-brake. Mine was fairly lame, but maybe yours actually works and has warped so much it drags when "released".

Limp-by fix is a can of spray grease. Work it into the spindle bearing. Doesn't work miracles. Usually can't get near the top bearing because the pulley hides it.

If you have a grease gun, try it. But the grease fittings are typically hidden, cheap, and clogged. And if the spindle has gunked-up, the bearings are already mostly-shot.

Fix-fix is $60+ for a spindle, and maybe some annoyingly seized-up bolts.

[PRR]

> burn out the clutch material until there's no adjustment left?

My 1974 Craftsman's clutch may be on its last leg. I would not yet worry about a this-century Deere.

[Willabe]

Thanks PRR.

BTW,   


        HAPPY   BIRTHDAY!     


Saw it on KOC's.       

[Willabe]

Hi guys,

I would not yet worry about a this-century Deere.

Nope, sorry, I should have been clearer, 1985?           Kohler engine, 38" cutting deck. It's really in pretty good shape, almost _no_ rust any where, nuts, bolts, shafts, pulleys, even the body and it's JD green paint, and it still really scoots in 5'th gear.  

Part 1 Sat.,

Well my wife's son, Matt (17) and I took it apart Sat. and I gotta say that he was pretty helpful.       He's taken 2 years of auto shop in HS and I think his problem solving is pretty good, but I think his hands need more time to develop better. The other thing is he seems to move in slow motion going to get a wrench or the oil can or whatever.        But he's still young, he should be more than fine, better than me!      

Anyway, Matt and I found the PTO clutch had _NO_ clutch material left and was just into the shaft plate it mates to. Blade spindles spin freely, no slop or play, no dry sound or rubbing/scraping noise when rotating and the grease in the bearing still feels smooth and not lumpy/caked or dried up. I don't see any blade brake.              The shaft (hollow, 9/16"x 4"x 1/8") that the blade spindle tension pulley yoke mounts on had two 1/16" wear marks on (opposite sides) and that's why the pulley arm was tilting. Ordered a new one from JD, $14.94, should be in on Thurs.

Part 2 Mon.,

Went and picked up the PTO and 2 belts from JD.

Also since we had the deck down/out (came out very easy, 4 round pins with cotter pins) I bought 2 new belts. 1 was for the rear wheel drive ($31.14) and was really not too bad (the tension pulley spring fought us a little but we got it) , the other was for the blade spindles ($22.47) and was pretty cracked/dried up. The 3'rd belt looked _almost_ new and connects the PTO drive pulley to the blades spindle pulley, so I let it stay. I thought it was best to put in the new belts while it was apart and I had easy access to them.

One more thing is the steering had gone wonky so while I had it apart I pulled the front wheel axle steering yoke and guess what I found?      

The kids (and maybe my wife?  ) had bent the steel yoke on one side. I think they did it by not paying attention when cutting close to the landscaping timbers for the raised bed gardening boxes. This is why I bought an _old_ JD instead of a new one.

My friend and neighbor, Red is 74 and is one of the hardest workers I've ever seen (for a guy that's only 5'10") 40+ years on the Rail Road as a maintenance man, everything from digging in the track ballast in 90+ deg. to -0 deg., plumbing, copper gutters, furnaces (including being on call in the winter when the stations heat went out in sub zero weather in the middle of the night and all the water pipes froze, so fix the furnace _and_ fix/get the water flowing so the station could stay open), making/welding iron staircases for the stations, re-doing bridge supports/pylons, from wood to concrete footings by lifting the _whole bridge_ with many 20/40 ton jacks and taking out the old wood and then forming for the new concrete footings, etc.....

I love this man like a brother/Uncle/Father and a friend. He's taught me a lot.

Anyway Reds going to try to straighten out the yoke. Worth a try, if he can't (and I bet he can) I guess I'll have to buy a new one, but I'd bet that a new JD yoke will cost at least $100.    

The new part should be in on Thurs. so I'll let you know how it comes out.


               Thank you,    Brad    


Here's the steering yoke, part #1;

[Willabe]

Well my friend, Red and I went today and picked up the tension pulley shaft that I'd ordered at JD on Mon. and put it back in the mower deck, put the front end back together and then put the deck back in.

I called JD and priced a new front axle and it was $285.00 + tax                     so we talked about it/thought about it for a day or so and decided to try this.....

First off...  Red _was_ able to straighten out the front axles (yoke) "wheel arm" pretty darn good IMO, but not _only_ was 1 end of the axles/wheel arm bent up & back (right side when sitting in the drivers seat), _but_ the center shaft (balance/pivot point) that the whole thing mounts to the frame with and allows the axle to move up and down (left wheel/right wheel) with the terrain, was also bent pretty bad. But he was able to straighten it out too by sliding a piece of steel pipe over it to bend it back in place.    

Next we thought the front axle (yoke) should be _Beefed_ up a little to _help_ make it a little more,    DRIVER PROOF!              So.....

He striped off the black JD paint with a wire brush on a 4" grinder (which he said "was the toughest paint he's ever tried to get off") so he could weld some 1/4" flat mild steel bar stock he had laying around. Look at the drawing and the red is the 2 pieces on the 1 side (front) which is the stronger side (U shaped channel side) and he also welded in a full length piece (end to end of the axle/yoke) of the same stock on the JD flat sheet stock that they welded over/on top of the U channel. The blue, (where I could draw it in, he welded all of it, both top and bottom) is where he filled in the missing weld beads that JD left out between the U channel and JD flat sheet stock when they welded up the axle/yoke.

Then he cleaned up the welds and put 2 coats of black rustoleum (?) on it.

He had a can full of zerk grease fittings in his work shed, so.... he also changed out the 3 zerk grease fittings and greased it up nice, put the wheels back on and filled them up with air to 14 PSI as the tire says.

I'm sorry I didn't take pics of all of this, just wanted to get it done.

Over all, steering is fine, now! Cutting is much better, but it still slows/bogs down a bit too much when blades are engaged/cutting.

Red and I think it's the carburetor that's off and is robbing power when a load is on it, ie, blades engaged ? I think I'll try runnig some carb cleaner through it first and then in the mean time research more on how to adjust it????

Didn't ask for a dime, helped me put it back together, now you see why I call him my friend and much more!

BTW, he used his good SS welding rod to boot.      

Now, I did give him the Monkey Wards AC welding machine 5, maybe 6 years ago and he Say's it's fine for home use, but he'd love to have an AC/DC to run it on DC with opposite polarity, Red's told me many times he likes that better.  
I also just gave him a cement mixer on wheels, _heavy_ steel mixer barrel and bigger mix load then you can find at any big box store, + with brake lights and that'll hook up to a trailer hitch, in trade for this work, and I will make up any difference to him for sure.

Let it not be said that I FORGET MY FRIENDS!    


                         Brad      

[PRR]

You don't adjust mower carbs much. Diddle the idle-mix, but the FULL power mix is pretty much built-in by jet size.

First of course, any full-power problem, check air filter and gas filter. The filters can be 90% clogged and it will idle slow, 80% clogged and still hold governed speed no-load. My mail-truck would cruise all day on the level, but lean-out up hill, until I blew a bunch of yuck out of the fuel filter. My sedan will grocery-hop with a gunked air-filter, I don't notice until I need the last bit of top-end power to merge onto the freeway.

Then clean any external governor parts of clumped grass.

Unless you feed it garbage, carb cleaner won't help. The passages are large. If there's dirt inside making trouble it's too big and inert (dirt) to wash out on the engine.

Most lawn-tractor engines are simple float types. In theory you adjust the float. In practice, with the rubber needles we use the last few decades, I've never seen a carb be "out" by much or run better when "just right". They are pretty tolerant and robust.

An exception I've seen: let water get into the fuel bowl and freeze. The float collapses. This would probably lead to 10,000% rich and no-start (after you get the water through).

Get a carb gasket kit. Take carb off. Start unscrewing and un-hooking stuff. There is a main jet usually in the bottom of the bowl. There could/should be a hollow tube threaded up from the bottom at an angle into the main air passage (alternatively: a tapered needle that moves with the throttle; or multipple venturis in the throat). That's the full-power system. There is also an idle system, an air bypass from the top to the throttle area and a tiny jet or needle. All these holes and passages must be clean. Most are _precision_ size, you can't just hog a 1/8" drill through to clear them. Poke gently or find new jets in the carb kit. When you see the size of the jets, you'll know how clean everything needs to be.... not clean like the crank bearings of a 7500RPM race engine, but nothing that will catch in a jet.

[Willabe]

Thanks PRR.

The first thing I did was change the air filter, in-line fuel filter and the spark plug.

I did a search and found this site on small engines, but I can't get the exact post to paste here, it was cleaning/re-building the carb on a JD STX38, if you go here and then search; John Deere STX38 Kohler 12.5 it should come up at the top of the list. Question was posted July 21, 2008 by Tony.

http://en.allexperts.com/q/Small-Engines-Lawn-1746/

It also back fires some times when you turn it off, which seems to be mentioned in carburetor problem questions.
  
From the info I've now read, it seems easy enough and I think I can re-build it. Just gotta go get the re-build kit from JD.

1 question, most guys seem to say to use carburetor cleaner to soak the disassembled carb. in over night, but 1 guy said carb. cleaner it too hard on it and you should use brake cleaner? Doesn't make sense, that's what carb. cleaner is for isn't it?    
  
BTW, I like to use guitar string end cut-offs that I save when I change my strings for cleaning out small holes. (My dad saw me changing strings 1 time way back in HS and came up with the idea.)


                Brad


Here's the carb drawing from JD;  

[PRR]

> back fires some times when you turn it off

You do NOT want it to do that. I thought it was harmless, but (so the story goes) a guy in the next town put the tractor in the garage, it backfired, the garage burned down! BIG garage, big loss.

I have doubts. Was it parked on oily rags or dry sawdust? However the insurance company seemed to accept that part of the story (but got uppity when they found she had a studio in the garage and had sold a painting.... "undeclared commercial use"??).

I think B&S engines used to run richer, were leaned for smog, and now backfire. The "fix" is your part 11, a fuel cut-off solenoid. I guess it gets grit, and doesn't cut-off fast enough to starve the engine before backfire.

It isn't clear to me from that picture just how it manages fuel-mixture; but not that many parts, you don't need to understand, just get them clean and snug.

Yes, guitar string is a good poke for most jets. Be gentle, push dirt don't gouge brass.

IME, Brake Kleener will dissolve stuff that Carb Cleaner won't; I think Brake is much more aggressive than Carb. Brake will take off paint and craze plastics that Carb hardly touches. Considering all the plastic in a recent carb, I would not start with Brake stuff.

> soak the disassembled carb. in over night

If it is hard-filthy or impossible to get into, overnight; but the critical inside parts of a mower carb are usually pretty clean and easy. Spray and toothbrush the outside so you can handle it without getting outside dirt inside. Use the spray-tube to be sure fuel or air passages really go somewhere (not blocked). Wipe out, preferably with something that won't leave lint to make trouble (old well-washed linen sheet?).

Similar problems and sorta-useful answers:

http://www.justanswer.com/small-engine/5cx4r-john-deere-stx-38-lawn-mower-13hp-kohler-working.html
http://www.justanswer.com/small-engine/6fumv-stx-30-riding-lawn-mower-having-trouble-starting.html

The comment about alcohol-adulterated gasoline may be relevant. Alky-gas has been around a while, but maybe the "alky-resistant" plastics in an older machine weren't really up to modern corn-lobby fuels. (But I didn't see any swollen parts in my 1974, which sure predates wide use of corn-alky "gasoline").

[Willabe]

It isn't clear to me from that picture just how it manages fuel-mixture

Here's from the parts list.
13 ........ VALVE 1    
14  VALVE SEAT 1    
15 M93412 JET 1            -MAIN
16 M93239 NEEDLE 1    
18 M93403 SCREW 1      -IDLE SPEED ADJUSTMENT

We park it in a small shed 50' or so from the house, hopefully when I get the carb cleaned up it'll stop doing that.

I've always used regular from the Mobile station a couple a blocks away. Red and another friend both told me they mid or high grade in all their small engins. Looks like I'm going to change to at least mid grade.  

I read the links you posted, thanks PRR.

The links back up the fuel grade change and what you said about the plastic parts swelling.


                       Brad        

[PRR]

> from the parts list.

Not enough parts.

A simple air/fuel mixer with fixed fuel orifice, well, the air-suction goes as the Square of air intake rate. Double the air per second is *FOUR* times the suction, four times the fuel. If the mix is right at say 10HP, 12HP will smoke bad and 7HP will be too lean to run. While a lawn tractor may run only two RPM (1800 idle and 3600 working), still the "working" condition varies from 2HP (self-friction) full-throttle in Neutral to 5 or 6HP normal cuttings to 12HP high-grass up-hill.

There's a zillion ways to fix the mix; a dozen in common use. Tapered needle lifted by vacuum (SU) or throttle (many motorcycles). Multiple venturis. Back suction. Miller's multiple jets. My fav is the emulsion tube used by Weber, Holley, and oddly on my Craftsman.

Few of these schemes will go the whole way down to idle. For that you need a smaller carb. Usually there is a second air passage, maybe 1/16", around the throttle. This has a fuel jet/needle. It is designed for a very-rich mix. Actually: the right fuel but not enough air to idle. Your #18 cracks the throttle plate for the additional air needed. #16 may adjust idle fuel orifice, idle air, or idle air bleed. The combined fuel-air idles and carries the engine just above idle, until the main system picks up enough suction.

On top of that: for 5HP to 10HP you want "economy" mixture but for 12HP you want a richer "power" mixture. Partly to make use of "all" the air, but also to cool the hard-worked engine. Several ways to do that.

In livelier rigs you also notice that when you mash the pedal the air flow comes up faster than the fuel. Lean, stall. An acceleration pump gooses some fuel on rapid throttle opening. I think many mowers omit this; idle rich and expect you won't demand instant throttle response.

NONE of this matters to YOU. It worked once. Carbs are not high-wear parts. Clean everything good as new, it will work like new.

Other thoughts:

http://www.tecumsehenginetroubleshooting.com/tecumseh-l-head-engine-troubleshooting

http://www.tecumsehenginetroubleshooting.com/carburetor/troubleshooting-tecumsehpower-carburetors.html

[Willabe]

NONE of this matters to YOU. It worked once. Carbs are not high-wear parts. Clean everything good as new, it will work like new.

Ok, a cleaning I will go.      

One more thing, I had the fly wheel off with the magnito (?) on it. Is there any adjustment for the spark from the magnito (timing) other than the fly wheel being keyed to the crank shaft?

Thanks PRR.


                           Brad      

[PRR]

> the fly wheel being keyed to the crank shaft?

Be sure that key is healthy. If sheared, no-go; but apparently it can be "bent" which will cause a timing error.

In most small engines there's no timing adjustment. If it has points, get the gap right or there is a small error; however "most" running machines are electronic spark without points.

> the fly wheel off with the magnito

Strictly, only the magneto magnets are on the flywheel. The magneto coil is on the engine. Fat wire to plug, thin wire to kill switch (or key switch). and classically a thin wire to the points. I dunno how electronic ignition integrates the pickup, amplifier, and main coil. (I may find out: the neighbor got a $100 rider/beater and has been cranking it for 2 days...)