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Lifetime Lawn Guy
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Discussion Starter #1
Another project, on a mower I've owned since '94. Bought it new when I was a sophomore in high school! I have not used it much at all in the last 5 years or so, it just camped out in the shed, I'd fire it up once a year or so, that was about it. A friend of mine bought a house, needed a mower, so I loaned it to him. He called last night said it started cutting out and then died after he turned it around from one pass to the next. Had been running fine before that. Fired it back up and the RPM's were insanely high he said, screaming. He killed it. Looked it over a bit, fired it up again, it ran fine, but still somewhat high on the RPM's. (almost 4,000 when I checked it).

I have an M-series service manual, but someone prior to my owning it removed the carb and govenor sections! :banghead3

The govenor I assume is adjusted by bending on the linkage where the lower end of the spring attaches. At least I was able to bend it up, removing some tension from the spring, and getting the rpm's down to 3600 (I'm sure it's supposed to be 3200-3300 though) but 3600 is ok with me. After it was running a while on the bench and got good and hot the govenor started hunting, not fast, but kinda slowly, back and forth. Never did that before...

Of course I post this and it's still dissassembled. I pulled the carb off and the engine shroud, cleaned everything with the air hose. There was a good bit of oil/dirt under the flywheel around the oil pump. Not sure if it's the top seal leaking or the oil pump?? I cleaned the carb, but haven't pulled the bowl off. I don't have gaskets for this one. I shot some carb cleaner in it after removing the mixture adjustment screw as well as the jets. Hoping it was just a tiny something that was causing the issues.

I will see what partstree says for the oil seal, hoping its the same as all the others, but this M engine is a whole different animal for sure! In all the years I've owned it I've never touched it other than just routine maintenance.

Another issue is that when cold starting, if it dosn't fire in 2 or 3 pulls the plug ends up soaked with fuel, then won't start at all. May be caused by the WRONG plug, it's had a rj12yc plug in it for years... Put a CJ14 in it, hope that will solve that?

A couple bad pics of it (still forgot to clean my blackberry lens) It really dosn't look that bad in person! I want to shine up the paint and clean the Toro steel wheels up and possibly paint them orange, just for giggles...

If anyone has a dead one they would be willing to part with a handle peice from, One side of mine is bent. Long story goes with that... It's always bugged me that it got bent!
 

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Lifetime Lawn Guy
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1,426 Posts
Discussion Starter #2
Ok, I also question if the coil is going out, perhaps causing the weak spark when starting... The coil is oozing, almost tar-like sludge, the upper portion facing the flywheel appears melted. I'm still new to diagnosing coil problems, so is this the sign that it's going out?

I found a number of them on ebay, of course prices range from $22 to $60 roughly. Some look different than others. Should I stick with one that is most similar to what's on it or does it matter as long as the part number is correct?

The oil seals appear to be something different, of course... I have about 30 of the "standard" seals and this one takes some odd-ball that I've only found on partstree for $8.32 each! Plus their high shipping... But I just don't know if the oil is coming from the seal or the oil pump itself? can oil even leak from the pump or is it totally sealed?
 

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2 stroke enthusiast
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6,568 Posts
Sounds like maybe it was running hot or lean causing the surging and partially melted coil. I've never seen that, oozing or what you described. The CJ14 is the correct plug. The oil pumps are completely aluminum with a steel plunger, though the ones I've seen or own don't leak around the pump instead will weep oil from the lines at the pump connections and the oil check valve at the carb. After replacing lines on my 10591, I finally got the oil seepage stopped around the tank feed nipple and pump, now it's on to the check valve connection. May get to it today. Oil seals tend to be quite long lasting on these M's from what I've seen. Have yet to see any, top or bottom leaking oil or heavy buildup or dirt/grease in the areas. There is grease(somewhat) found under and around the oil pump for lubrication from the factory and periodic maintainence you should do when removing the flywheel for inspection. Sounds like you need to pull and thouroughly clean the carb. If you remove the bowl carefully, you can reuse the gasket. These Mikunis are very sensitive to contamination of any kind, dirt, water, etc. Hope some of this info helps you in some way.
 

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The Sea of Green Machines
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4,767 Posts
It takes the same coil as Duraforce. I replaced mine early this year. I think when I replaced it I got the governor out of adjustment as It doesnt throttle down when hot now and sticks. I was too worried about breaking the fuel tank or oil lines that I didnt pay attention to anything else.
 

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Nice Toro comm wheels on that 10590. Someday I'd like to get the "radial" treaded rubber like yours to replace the "mudders" on my front wheels.

Looks like you've got answers on the coil and oil.

I have an M-series service manual, but someone prior to my owning it removed the carb and govenor sections! :banghead3
It's still available on-line. Go to the Lawnboy Support Page, find your model/year and click on the "manuals" button. It's labeled "Lawn-Boy M-Series WPM Service Manual [ English ]", filename lbwpmm.pdf, Chapter 4 describes setting/adjusting the governor.

Chapter 3 details the oil injection pump lubing that Echoman mentioned above.

Sounds like you need to pull and thouroughly clean the carb. If you remove the bowl carefully, you can reuse the gasket. These Mikunis are very sensitive to contamination of any kind, dirt, water, etc.
:ditto::ditto::ditto: what Echo said... (actually, "very sensitive" could be a slight understatement! :banghead3) Try checking the governor first, but the hunting does sound like the carb could be unhappy about something.

I'll also endorse one particular line of MTF preaching: consider adding an in-line fuel filter. Combining that with a regular dose of Vitamin 'S'eafoam has pretty much eliminated my M's carb clean-up needs.

The oil seals appear to be something different, of course... I have about 30 of the "standard" seals and this one takes some odd-ball that I've only found on partstree for $8.32 each!
heh... being so "unique" has its ups and downs... Try mowpart.com for parts (613182 Seal - Oil Sm: $5.40 +sh); they often have to first get it from Toro then ship it to you, so I'd verify actual availability over the phone first. There's also a few MTF members that are dealers.

Good luck! :trink39:
 

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Lawnboy fixer & user
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530 Posts
Mechanical governors can cause surging, or the throttle can hang up if any of your linkage is sticking. It all has to be free moving, including the link to the oil pump.

Love those Toro tires/ rims. As heavy as the M is, it's got to make a difference in pushability, handling. Any special changes getting the rear drive wheels to fit? Looks like a good heavy duty option for an M!!
 

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Lifetime Lawn Guy
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Discussion Starter #7
Just tried it again after cleaning the carb (couldn't find anything in it) but sprayed it carefully with carb cleaner several times over and blew it out with the air hose. Cleaned all the linkages including the oil pump under the flywheel. Everything feels very free, and nothing has been touched to cause it to start hunting that I know of.

It's still hunting just like it was though. No change. Only thing I notice is that the govonor rod where it goes into the engine is pretty loose, has play in it up/down, side to side. Not sure if that was always the case, but I'm sure it didn't just wear out overnight.

The toro wheels bolt right onto this model of M, since this is a post OMC model. Same gear and everything. Just the "dust cover" had to be swapped from the toro as well, then modified slightly (the dowel that goes into the side of the height adjuster) had to grind it to a smaller diameter to fit. Did that mod years ago after I had broke 2 drive wheels, cheap plastic, HEAVY mower.
 

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The Sea of Green Machines
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Is it super humid there? Surging can be as simple as extremely humid air.
 

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hmm, gooey coil... yea it sounds toast from the heat, ballasts do that in flor. lights too..
um, if you have to open the carb&clean, might be some dirt on the float needle,or its orifice, i had that& i cleaned the needle&orifice with den.alcohol&a q-tip seemed to smooth it out & hasnt came back yet
i agree with ft, it's been extreme humidity here& i sorta get a teeny surge from the mowers, but when it was a cool for a day or 2 last week it didnt do it
 

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Lifetime Lawn Guy
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Discussion Starter #10
Not much humidity here, just 105+ temps. I think I figured out why it's surging though, but haven't been able to test it. When I lowered the RPM's I just bent the arm that the spring attaches to. I know, really poor explination there. But anyway I think that govenor spring dosn't have sufficient tension now to "hold" itself. At least that's my theory. I just need to loosen the govenor linkage where it comes out of the side of the engine and give it a small turn to lower the full throttle RPM's. Always a pain, I always forget which way is to increace and which way to decreace, and it's so touchy to get just right.

I really wish my M-series service manual wasn't missing the govenor and carb sections! I found and ordered another manual today though... I'm sure it details the correct way to adjust the RPM's. What I'm still fuzzy on is what made it start running so much faster suddenly.

Didn't get much done tonight, friends stopped by and not much of anything progresses at that point, lol.
 

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2 stroke enthusiast
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Sounds like a good govenor re-setting is in order. You can download the info from LawnBoy's site. Luckily, I've not had to mess much with gov settings on either of my 2 M's. From what I can tell, though never opening an M series case, I believe the govenor is made of cast steel along with steel ball bearings. Don't think there was any nylon or plastics used in this assembly to really fail?. I'd still REALLY like to know who infact made this engine? Was it a Suzuki design or another Japanese engine builder or did Toro actually R&D and build this model? Things that make you go hmmmmm?!
 

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I really wish my M-series service manual wasn't missing the govenor and carb sections! I found and ordered another manual today though...
Scroll up in this thread to Post #5... The complete service manual for the 'M' is available on-line. You can print the whole thing or just your missing chapters.

Edit: here's the relevant part of the post...
Go to the Lawnboy Support Page, find your model/year and click on the "manuals" button. It's labeled "Lawn-Boy M-Series WPM Service Manual [ English ]", filename lbwpmm.pdf, Chapter 4 describes setting/adjusting the governor.

Chapter 3 details the oil injection pump lubing that Echoman mentioned above.
 

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this is interesting-the gov has failed on my oldest suzki so things CAN go wrong with the internals on the gov assembly. i think echo is right-the more i look at the m engine-i suspect it really a japanese desighn as no american lawnmower engine i have seen is even close to this complex desighn. there is a history of japanese engines being sold with american names-the briggs 2 cycle- the briggs europa-etc.....
 

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2 stroke enthusiast
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Oh, sure govenors fail Dan, as I too experienced a worn one on a Toro 2 cycle dated back to the mid 80's earlier last year. The guy was getting frustrated that we(shop) couldn't get it to idle right, etc. I told him we could definitely fix the issue with replacing the govenor, but he didn't want to spend the money/shop rates to get it done. Anyway, not sure other than the ball bearings what composition makes up the M's govenor assembly. I've got a good spare M engine I'd be willing to part with(any takers?) or may just even crack it open and have a looky in there-maybe replace seals while it's split.
 

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Lifetime Lawn Guy
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Discussion Starter #15
The information keeps coming on this thread! I'm waiting on the LB site to spit out my manual, it seems to be SLOW, or not responding...

Like I said I'm going to *try* to reset that spring tension and then adjust the govenor by loosening the linkage on the govenor shaft. Hoping that will get it back in business. But Im also afraid that perhaps something is failing, causing the rpm's to jump up in the first place.

They are good engines, that's for sure, but yes, kind-of complicated. The oil injection system is a small part, but certinaly adds to the confusion with how it connects to several linkages.

My friend was asking me last night about a mower, said his back yard is getting tall now! Of course he refuses to use a staggered wheel mower and also one that's not self propelled. Mind you his back yard is about 3,000 sq. ft. What a lazy bum...
 

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echo-i am relieved to hear that the gov can fail on a suzuki-i thought i might be nuts! i have tried everything there is to get it to work right but failed. this engine still is sound otherwise and this winter i will tear into it and see if i can fix it. i have several dead suzuki to get the gov internals from.
 

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Lifetime Lawn Guy
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Discussion Starter #17 (Edited)
Alright I shot a little video of my fingers wiggiling the govenor rod, where it comes out of the engine. I don't believe there should be any end play in this, and mine moves around quite a lot. Without cracking it open I'm going to go out on a limb and say that something has failed. Either the bearing has worn out, or came apart, or whatever it's attached to on the other end has came loose. It still pivots freely, and the engine runs fine if I can just hold the govenor with my hand to keep it steady. Otherwise it's just surging constantly.


http://vimeo.com/13895297
 

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Lawnboy fixer & user
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Just saw your video, and checked my 10591. Mine has some slack like yours, no leaks, but has good reaction and works AOK.

Is your carb responsive to slight throttle changes without bogging if you use your finger to open the butterfly? Just wondering here.

Also the governor linkage to the carb and oil pump should push & pull very easily by finger pressure. Any sticking or tight movement, and the governor can overcompensate, or over rev. You may have to remove the spring to check.
 

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Lifetime Lawn Guy
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Discussion Starter #19
Yeah, the carb is really responsive, idles fine, goveneor dosn't hunt at idle. Actually I can push the throttle up and it will run smooth up till about 2800 to 3000 rpm. Of course that's just sitting on the bench.

I've cleaned and checked and re-checked that all the linkages and moving parts are free, everything seems fine. I'm kinda stumped here...

The LB website refuses to load the service manuals for some reason too...
 

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2 stroke enthusiast
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I've got some back and forth play on my 591, but not so much side-side or up and down play. You may just have to open it up and have a look.
 
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