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I won this MTD manufactured Yardman 42" ride-on mower back in 1990. It has a 12.5 HP BS engine, and served me well until the 7 speed transmission slipped while traversing uneven terrain. I was in speed 7 at the time, throttle wide open. I should have throttled down, gotten off, and pushed my way clear, but, before I knew it, the tranny caught, and forced the engine to a sudden and complete stop. I knew right away that I had broken the connecting rod. This was probably 10 years ago (when I was 60 years old).

The mower has been stored in my garage all this time, and, now, at my age, I am less than enthusiastic about walking the yard (3/4 acres) behind my excellent Toro 21" walk behind. Our lawn has many trees which drop many, many leaves in the fall. The Yardman handled them with ease. Using my Toro makes them a chore of which I am growing mentally and physically tired (previous to the Toro, I owned a LawnBoy 2-stroke "Professional", best mower of any type that I have ever owned - but the deck failed structurally and separated the engine halves, no repair possible).

Based upon my positive experience with the Toro, I went shopping for a Toro ride-on replacement for my old Yardman. The unit that caught my eye was a zero turn unit having a 42" deck pricing out at around $2500. If I want to pick-up leaves, add another $800 or so.

My lowly Yardman came with everything I need to pick-up leaves. I still have those two containers that catch the leaves, you just hook them over the rear rail on the mower and you are ready to go. They add a couple of feet to the length of the rig, and I can stack them in a space about 3' x 2' x 4'. No massive tube with which to deal, etc.

The new Toro setup adds some 7-feet to the length of the rig, plus a collection bag, hood, and tube, and all of that will take up storage space when not in use.

So, I considered buying and installing a new engine on my old Yardman. YouTube videos show that it is not a complicated process, but, at my age, lacking a lift or other tools (that I see in use in the videos), I feel that it is more than that with which I wish to contend.

On my own, I estimated that to have a shop do this engine replacement work would be around $1,000.00. Checking with local shops has confirmed that my estimate is in the ballpark.

Most shops advise against putting that kind of money into this old machine, but, it has been garage-kept, all other components are in great shape, and it is a complete package for my needs.

So, in posting here, I ask your suggestion as to whether you feel I am foolish to invest the dollars to replace the engine in this machine as opposed to purchasing something new. I know that the Toro Zero Turn is not my only option, but to pay $1,400 - $1800 for something similar to what I already have whose leaf pick-up is not as clean and simple as what I have turns me off. FWIW, this Yardman expels cuttings from both sides, and uses two chutes (one on either side) to direct expelled cuttings (or leaves) rearward where the attachment of the collection "bags" will catch it, or, using easily attached deflection accessories will direct cuttings back onto the lawn. To me, it has always been such an efficient system, and my decision to collect or recycle cuttings never involved much in the way of attachments nor did that decision have any substantial effect on the overall footprint of my setup. The Toro collection arrangement really enlarges the footprint of the machine which is not good for my cutting environment.

I have two shops that will do the engine replacement within my budget, and they will also replace the belts on the cutting deck.

I know replies to this thread will be varied, but would appreciate your input and the logic behind it, as that will help shape my final decision. I am looking to pull the trigger on repair or replacement in order to ride this fall as I pick up my leaves, so I need to "shoot" the "gun" soon.

Thanks in advance for your thoughts.

Caruso

Bagging is generally a disaster with ZTR's
When my customers broach this with me the answer is always the same
Don't think about it unless you fit a lot of counterweights on the front and a Donaldson type 2 element canister filter
Even then you are going to get filthy and have lots of dust down you back.

I for one would go with the replacement engine.
Ask the workshop to make sure they apply plenty of anti sieze on the PTO shaft .

It sounds like for your use I would consider putting a new engine on your old mower, but keep in mind that you probably should also have the tranny worked on to prevent the gear jumping that would were experiencing when the engine went belly up.

Have you actually verified the broken rod in the old Briggs? If so, any other damage to the motor that you can see? Might be possible to repair that motor for reasonable money. Normally you'd junk the mower and buy new but since it fits your needs perfectly I'd look into fixing what's there first, then look into a new engine.

tom3 said:

Have you actually verified the broken rod in the old Briggs? If so, any other damage to the motor that you can see? Might be possible to repair that motor for reasonable money. Normally you'd junk the mower and buy new but since it fits your needs perfectly I'd look into fixing what's there first, then look into a new engine.

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Thanks to all for the replies. Yes, I verified the broken rod, and I was on the mower when the tranny slippage and subsequent 're-hook-up' caused the engine to stop in its tracks from full speed to nothing. I knew right then that the engine was toast. It could not be spun by hand.

I was quoted $1,100 for a new engine installed including all new belts, new battery, and sharpened blades. I have watched some videos on how to replace the engine and, likely, could have saved the labor expense, but, at 69 years of age, decided to spend the money and take the easy route for this repair.

The unit should be completed and back to me today (8/8) or Monday at the latest. I know the shop, and their workmanship is always honest, reasonably priced, and of good quality. I had with the shop this very same discussion, and they, ultimately, agreed that, given my situation, repair was a logical route to take. I think it says a lot for them, as had I opted for a new unit, I would have purchased that Toro setup from them.

Money was not a problem for me, and, for sure, this MTD made unit is a far cry from the Toro for which I lusted (will lust). But, in the end, I figure that the MTD will be like new when I get her back, and, both machines are only useful to me in cutting grass or picking up leaves. I was always satisfied with the results I got from the MTD, and it is a monster at picking up leaves.

ILENGINE, I am ignorant as to how the transmission on this unit works, and will have to study it some to develop an understanding. I do know that it only slips in and out of gear when I maneuver the unit into really uneven ground (a 'ditch' that has developed near my property line due to water runoff). I'm guessing that the 'frame' (if there is such a thing on this mower) is stressed which causes the gear slippage. In those situations, it will slip out of gear no matter what speed is selected. If it 're-catches' in a low gear, it's no problem, If it 're-catches' in a high gear (I was in speed 7 when I messed up my engine), and you have the engine set at full throttle, that is where you run the risk of seizing the engine.

I can easily avoid these unlevel ground conditions, as I do not gain any time by trying to cut these areas with the riding mower, I'll just leave them for trimming with my walk-behind.

I truly appreciate the helpful replies. I'm looking forward to having my old lawn buddy back.

Caruso

The best way to describe the how the transmission works, is the input shaft is connected to a gear on the inside. On each side of the input gear is another gear which engages both sides of the input gear at all times. Between those two gears is a sliding collar with either two or four square edge teeth that slip into a notch in the gears on each side depending on which direction you move the forward or reverse lever. Those teeth and notches will wear the edge so that it is no longer square but creates a ramp which allows the tooth to slip out of the notch allowing lose of drive and then pops back into the notch moving movement again. The forward gear is normally the issue because it is the gear that is used the most but can also effect the reverse gear in some cases for people that back up a lot.

Are you mechanical at all,replacing an engine isn't that hard, getting pulley off old engine is probably the hardest part, the mounting bolts are the same and electrical not that hard, just be sure new engine has same diameter output shaft and same liength.
You can buy a new engine for around $500 or less if you look around.

gainestruk said:

Are you mechanical at all,replacing an engine isn't that hard, getting pulley off old engine is probably the hardest part, the mounting bolts are the same and electrical not that hard, just be sure new engine has same diameter output shaft and same liength.
You can buy a new engine for around $500 or less if you look around.

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Yes, Mike, I consider myself somewhat mechanical. I love cars and drive a 2012 BMW that was totaled in Maryland (they total cars there that have relatively little damage), have restored it, and modded it to 400 HP, but I had access to a friend's lift and tools, and I was 5 years younger at the time (change the alternator on a 135i if you want to experience true frustration).
I have reviewed online videos, and it looks quite simple, but I have no lift, am by myself, and was just not that motivated to take this on. I did check the price of the new engine and the cost of labor. I know and respect the shop, so, I decided to treat myself and let them to the work.
BTW, shipped from the factory, this mower was setup such that the blades would stop turning if you shifted into reverse (actually, I can't remember whether the blades stopped or the engine quit). I thought it a silly safety measure, so switched up the wiring to defeat that feature (and that was some 30 years ago, so I am fuzzy on the details).
Looking forward to getting the unit back. My grass is growing tall, LOL.
Thanks for the reply.

Caruso

I'd have gone with a new engine, too. I would have also tried to replace the connecting rod on the old engine. As a matter of fact, that's what I actually did this year ('94 MTD; 12.5HP single cylinder engine). First time I ever opened an engine and took a look. I could not detect any damage to the cylinder with a fingernail; it looked great. I opened 'er up cleaned it out really good and replaced the connecting rod. I did note there was A LOT of scoring on the cam shaft where the connecting rod rode, but whatever. I mowed my 1-1/2 acre yard and was a couple minutes from finishing when there was a clunk, the engine died, and smoke came out from under the ring gear. I figured that one cracked the case, too, so I replaced the engine with a 16HP B&S Vanguard V-Twin. The seller couldn't get the shaft bolt out, but my impact gun could. Unfortunately, it still didn't come off the shaft. That only made it a little bit more 'interesting' to get everything hooked back up. I just had to figure out which set of mounting holes to use. Runs better than before and is quieter, too.

In the end, I think you saved yourself some money and will be happy with the outcome.

CDelSignore said:

I'd have gone with a new engine, too. I would have also tried to replace the connecting rod on the old engine. As a matter of fact, that's what I actually did this year ('94 MTD; 12.5HP single cylinder engine). First time I ever opened an engine and took a look. I could not detect any damage to the cylinder with a fingernail; it looked great. I opened 'er up cleaned it out really good and replaced the connecting rod. I did note there was A LOT of scoring on the cam shaft where the connecting rod rode, but whatever. I mowed my 1-1/2 acre yard and was a couple minutes from finishing when there was a clunk, the engine died, and smoke came out from under the ring gear. I figured that one cracked the case, too, so I replaced the engine with a 16HP B&S Vanguard V-Twin. The seller couldn't get the shaft bolt out, but my impact gun could. Unfortunately, it still didn't come off the shaft. That only made it a little bit more 'interesting' to get everything hooked back up. I just had to figure out which set of mounting holes to use. Runs better than before and is quieter, too.

In the end, I think you saved yourself some money and will be happy with the outcome.

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Good to see that I am not the only night owl on this forum (or perhaps you live in a different time zone??).

I never considered trying to repair the engine, although I inquired about that option with the shop that is doing the work. They seemed to have no interest. I checked with a couple of small engine repair shops, but all were too busy to take on the work. I did consider asking for a bit more horsepower, but forgot to ask when I called the shop that is doing the work. For me, it's just as well. There has never been a time when operating this machine that I yearned for more horsepower. It cuts nicely through my grass no matter how tall I let it grow (I tend to cut it high, anyhow, as I feel most of the lawn services in my area try to leave the customer with a golf green cut - they cut it smooth because there is almost no grass left, then, as summer wears on and things dry out, their grass turns brown).
Congratulations on replacing the engine on your mower.
I am hoping to have mine back tomorrow (well, today, actually).
Caruso

CDelSignore said:

I'd have gone with a new engine, too. I would have also tried to replace the connecting rod on the old engine. As a matter of fact, that's what I actually did this year ('94 MTD; 12.5HP single cylinder engine). First time I ever opened an engine and took a look. I could not detect any damage to the cylinder with a fingernail; it looked great. I opened 'er up cleaned it out really good and replaced the connecting rod. I did note there was A LOT of scoring on the cam shaft where the connecting rod rode, but whatever. I mowed my 1-1/2 acre yard and was a couple minutes from finishing when there was a clunk, the engine died, and smoke came out from under the ring gear. I figured that one cracked the case, too, so I replaced the engine with a 16HP B&S Vanguard V-Twin. The seller couldn't get the shaft bolt out, but my impact gun could. Unfortunately, it still didn't come off the shaft. That only made it a little bit more 'interesting' to get everything hooked back up. I just had to figure out which set of mounting holes to use. Runs better than before and is quieter, too.

In the end, I think you saved yourself some money and will be happy with the outcome.

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I have never seen a cam shaft scored from where the connecting rod rode!

mower king said:

I have never seen a cam shaft scored from where the connecting rod rode!

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If I decide to tear it apart, I'll get a pic. That was the only place there was any scoring, and it was pretty bad. I don't know if it had anything to do with the second rod failure or not, but it's possible.

CDelSignore said:

If I decide to tear it apart, I'll get a pic. That was the only place there was any scoring, and it was pretty bad. I don't know if it had anything to do with the second rod failure or not, but it's possible.

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The connecting rod can score the crankshaft, not the camshaft!

mower king said:

The connecting rod can score the crankshaft, not the camshaft!

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Whoops! My error! LMAO!

Now we're getting the picture..

FWIW, I managed to find the users manual for my mower. The model is #13607-7, and the HP is shown as 12 HP (could swear that my engine says 12.5 HP, but do not have the unit at this time to verify).
Some interesting information about adjusting the height of the deck wheels, and the mower was manufactured in 1987, anything to the contrary I may have posted not withstanding.

Hoping to have her back today. Shop is overdue, but given the times in which we live, I find that acceptable.

There is a plastic nameplate that mounts onto each side of the hood via two "posts" that snap through holes in the hood. I'm missing the left-hand nameplate which fell off years ago (I probably have it squirrled away someplace "safe", which is why I went digging for the owner's manual. If anyone has a clue on where to find that little part, I would appreciate a heads up. The part is not even mentioned in the manual, and the hood comes up as not available on most websites. Not a big deal, I may just remove the right hand name plate so that she is "balanced."

Thanks for all the replies.

Caruso

Auto parts stores have what is called "emblem tape" that is made by 3M I think. Really good stuff, dark brown to black and had a red pull off plastic strip. That would put that nameplate back on forever. One thing to watch on the motor swap is the battery voltage while running with the blade on. Charging systems vary quite a bit and if your mower has an electric blade clutch it takes a better unit.

tom3 said:

Auto parts stores have what is called "emblem tape" that is made by 3M I think. Really good stuff, dark brown to black and had a red pull off plastic strip. That would put that nameplate back on forever. One thing to watch on the motor swap is the battery voltage while running with the blade on. Charging systems vary quite a bit and if your mower has an electric blade clutch it takes a better unit.

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Thanks for the reply. Unfortunately, I cannot find the missing nameplate, so, either need to locate another, or remove the remaining. I feel confident I could get a couple of decals if needed.

Caruso

Happy to report that I picked up the mower yesterday morning, brought it home and proceeded to cut my lawn. Still cuts like a champ although yours truly is a little rusty after ten some years. I missed a couple of spots on the lawn, and I was very shy around trees and uneven terrain. I'll get better, LOL.

The engine they installed is 11.5HP, not 12, but I don't really care. The machine has plenty of power. I am so glad to have her back. This unit was manufactured in 1987, so that makes her 33 years old!! Given the new engine and new belts, she is running like new. If I am careful not to screech the engine to a halt, I should have no further issues with braking the connecting rod. That was my fault, and I knew I had screwed up as soon as it happened. Looking forward to spending the next 33 years with her (don't you dare laugh!!).

Caruso

One more thing, and I am certain that it has been asked on the forum a thousand times, but at what interval would you change the motor oil, and what would you use. I lean towards full synthetic, but would appreciate some comments.

Thanks.

Caruso

carusoswi said:

One more thing, and I am certain that it has been asked on the forum a thousand times, but at what interval would you change the motor oil, and what would you use. I lean towards full synthetic, but would appreciate some comments.

Thanks.

Caruso

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I would use B&S 30 with a B&S engine and we tell everyone that buys a new mower from us,change engine oil & filter every 50 hrs or once a season, whichever comes first!....and check your eng oil before each use, it's real simple to just, pull the dipstick and check. You don't want to lose another rod!

Today's motor oil is formulated for use in newer designed automobile engines, quite a bit different that what an air cooled lawn mower engine would use. For no more that the mower uses and how often it's changed I'd use the engine maker's oil in the weight required. There are some synthetics - from them - but I'm not a big fan of those for air cooled engines.

MowerKing and Tom3, thanks for the advice on engine oil. I have no problem buying B&S oil from the shop that fixed my mower. I assume that, since you didn't mention it, there is no need for an early oil change on this engine (as in break-in oil change). If you disagree, please advise. At the moment, I am very pleased with this unit (and I continue to advise the growing number of physicians I need to see these days that I expect them to keep "this" machine running like my Yardman for the next 40 years - don't you dare laugh!).

Happy mowing.

Caruso

Not laughing here. Every time I get a checkup I have to eliminate something from my diet seems like. Carbs, salt, sugar, latest was major cut in milk drinking. Probably wind up raking the lawn after mowing and having it for dinner.

I use the manual's recommendations as the max amount of time before I change the oil. I check the oil each time I start the engine. When the oil gets real dirty I change it even if it is way before the recommended time. There have been times I changed the oil 3 times before the recommended time. As far as using synthetic, again, it all depends on what the manual says. I've been using 10w-30 for as long as I can remember and have never had an engine blow up or die. Maybe its because I change the oil when it needs it.)

AaronZ said:

I use the manual's recommendations as the max amount of time before I change the oil. I check the oil each time I start the engine. When the oil gets real dirty I change it even if it is way before the recommended time. There have been times I changed the oil 3 times before the recommended time. As far as using synthetic, again, it all depends on what the manual says. I've been using 10w-30 for as long as I can remember and have never had an engine blow up or die. Maybe its because I change the oil when it needs it.)

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As a rider of vintage , veteran & classic motorcycles, it is something I say almost daily.
What oil you put in is no where near as important as the stuff you just took out and the frequency of doing it .
Mower oils should be changed annually , at the end of the season after the last mow.
You seem to understand this quite well & have been justly rewarded.
People are rather strange beings and always looking for the magical silver bullet even when they have the know reliable musket in their hands

If the engine doesn't have an oil filter, I'd change the oil after the first five hours, then annually if no more than 50 hours are are put on the mower per season.

If you don't have an hour meter, you'll have to estimate how many hours you're using the mower per season.

Update on my experience:

New engine runs fine, new belts have eliminated the tranny slippage. I used this setup to pick up my leaves last fall (we have many trees and many fall leaves to pick-up), and, so far, have cut my lawn this spring without incident. I know my rig is no Toro, but it is doing the job for me. Thanks to all for your helpful replies.

Caruso