Drug home a couple more Lawn Boys yesterday

Nov 23, 2015
On a whim I looked on FB Marketplace yesterday and saw a listing from a local backyard small engine mechanic for a couple of mowers that he wanted gone and were priced that way. One-a 70s or 80s F-engined self propelled model(no blade brake) was already gone, but the other two showed promise.

The first of these-I can't find a whole lot about it, and unfortunately it may be parts because there's a big chunk out of the deck that I didn't notice(wasn't really paying attention to it). It's a model 8125P, which apparently was a 1-year only model(1984) and was one of the few "square wheel" 2-strokes they made. It was also one of their first with geared self propel. This one turns over but I didn't do a lot to try and get it running.


The second was the real prize, though, and I'd hoped this winter to find one similar to it. This one is a 10547 with all the goodies-3 speed transmission, electric start(not sure if that works) and alloy deck.


It looks a little rough, but is basically solid. I was able to get it to cough a few times. The compression is a bit low(~92psi, manual says 80psi minimum) but I have the cylinder filled with PB Blaster now hoping that might free up a bit. I couldn't do a side-by-side with another carburetor/air box yesterday when I was playing with it, but I feel like something isn't right there(no big deal as I have another). Still, though, there's life in it and worst case I can pull a Duraforce engine off a rough deck I have and put it on here.

Pretty happy with these, and especially the fancy Gold Series one. I'm just debating about whether to even mess with the electric start...
I have an old 2000 model that just won't die. I have used it for leaf cleanup this year and the carb is not cutting off the fuel so I have to add a fuel valve. Otherwise it's incredible. But... I have alternative methods of cleaning up the leaves... ;)

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Nice mowers! For someone who works on a lot of lawn equipment I have yet to lay my hands on a lawn boy. They seem pretty rare around here, and those who own them usually know how to tinker with them.
Excellent finds indeed! I cannot wait to hear more on their progress. I miss having one around to mess with.
Will certainly keep this updated, and you know yours have a good home here-in fact just spent some time the other day doing a bit of welding on one of the decks. I've mowed a lot this summer with that one.

Good find. I feel it has to exhaust under the deck to be a real LawnBoy. Kind of like air cooled Porsches. Still using a LB from 1974.

I know some people dismiss the Duraforce engines as being "not real Lawn-Boys" because IIRC the engine was designed/put into production entirely under Toro ownership and also of course the top muffler. They're darn good engines, though, and very powerful. They also do exhaust on the bottom, but use a tube to carry the exhaust up to the top mounted muffler. None of them are exactly quiet, and the top muffler isn't exactly the best looking thing, but they're also quieter than bottom exhaust mowers. The Duraforce does have two important Lawn-Boy design features-a 2 cycle engine and a staggered wheel deck.

The current ones that are basically rebadged Toros I do have a problem calling Lawn-Boys, although I don't know of anyone around here who even sells those.
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Nice mowers! For someone who works on a lot of lawn equipment I have yet to lay my hands on a lawn boy. They seem pretty rare around here, and those who own them usually know how to tinker with them.

I've only really been into tinkering with them the past year(actually started when I posted a thread on here about 2-strokes in general and ended up buying two from @Wrenchturner44 who is local to me) but grew up using them. I should say I grew up using a 90s F-engine one, which of course is 2-stroke, bottom exhaust, on a staggered-wheel deck, and is basically what a lot of people would consider a "classic" Lawn Boy.

They seem a polarizing mower, and you'll find plenty of people-commercial mowers and small engine mechanics both-who claim they were junk from the start.

At this point, the newest 2 stroke Lawn-Boy is 20 years old. The used market would seem to indicate that they were still very popular right up to the end, as models like the 10323(mid-range Duraforce model, self propelled, single speed transmission) and 10525(alloy deck, 3 speed transmission, basically the same as the 10547 I bought above but without electric start) are not too difficult to find. To still be using one, though, like you said you do pretty well have to be willing and able to keep them running on your own. With that said, the engines are decently durable. I have one in pieces now that I want to rebuild and have the parts on hand-I tore it down originally because of a bad reed valve but found a stuck ring and scored piston so decided if I put it back together I'd just replace those.
I have a Duraforce 6.5hp Silver Series. It is among the best mowers I've ever used. It needs an overhaul, and the deck is now slightly cracked. But it's a lightweight, vibration-free monster that will power through foot tall grass without stalling.

I also have Snapper Commercial mower with swiveling front wheels. It needs that ability to turn, as it's too heavy to maneuver around any other way. Unlike the mighty Lawnboy.

Maybe I'll find an aluminum deck and update the Lawnboy. It is worth the effort.

Here it is when I flew my Cessna over to Venice FL to purchase it

A few years back I was in a group of LawnBoy owners and we would trade these mowers like Base Ball cards.
The Dura force I had was very powerful but smoked like crazy and never did run smoothly. I kicked the habit and I'm down to only one LB.
A 1974 with a magnesium deck has the side mount bag, when it gets too full it tilts the mower over and I'm on two wheels. I'll keep it forever even if it stops running.
Made some progress!

The 10547 is the one that's been getting most of my attention as it's the one that I really want to use.

I still wasn't making a ton of progress getting it to start and run, and finally spent some time really looking at the throttle mechanism.

First of all, I made a "well duh" realization that still was interesting to me. I have a tachometer on one of mine, and I'd noticed that when I'd throttle it down, once it settled from a throttle change, it would actually hold the speed regardless of load. I finally put two and two together, and realized that the throttle is MOSTLY just moving the mounting point of the governor spring and consequently just changing the governor setting. Only the last little bit of throttle closes the disk at the front of the carb body to choke it.

In any case, the throttle on the 10547 wasn't actually moving far enough to engage the choke. My others have a "click" in the throttle control that holds them into the choke position, and this one wouldn't move into that position(yes I did shoot some oil down into it and also cleaned out all the crud with compressed air). I tried making some adjustments, but it just wouldn't go far enough. Finally, I just took another throttle control from one of the 10323s, which are a totally different style but connect the same way and stuck it on. I have it loosely zip tied in place, but I do have the choke(I'll revisit the proper control-they're $50+ to replace completely).

It still was struggling to start, and I started wondering about the primer bulb as the one on it doesn't want to really spring back. Yes I should replace it, and I've ordered some, but for the time being I borrowed a full primer+tube out of the parts box and just have it dangling out under the gas tank.

With three squeezes of the primer and the choke on, it started and more or less stayed running with an odd resemblance to a steam locomotive. It was chugging a bit(and I could hear the lean surge these engines are known for) and belching tons of smoke. It was also backfiring.

I have no idea what was in the gas tank. There was a bit of gas in it when I got it, and not wanting to really take a chance on it not having enough oil, I'd added a little bit more. I suspect I ended up with too much oil, and finally just figured draining and refilling was the best idea. After running the carb dry, I put some Toro-brand 50:1 premix in it(I don't want to mix up 32:1 that I won't use until the spring now) and it started right away and ran great. I drug it around back and chopped up some leaves. All 3 speeds on the transmission work, and it's just a great running and feeling mower. I'm looking forward to using it in the spring, especially now that I know it will work. Oh, the lean surge isn't there, although I don't know if that will change on a 32:1 fuel mix. A 42 pilot jet fixed it on the other one I use, so I will try that.

So, now that I'm satisfied it's going to run, I get to work on the rest. I want to give it a good clean-up, maybe respray the deck, and of course do all the other general maintenance. I've found some on servicing the transmission(beyond pumping grease into the Zerks) so will do that. One of the wheels has no tread so I need to replace that or maybe all 4 of them. For that matter, I've read a bit on fitting commercial grade wheels(which have ball bearings) so may look into that.

I still need to decide what to do on the electric starter. Part of me is curious to see it working, and I'm hoping I can test it with just any 12V lead acid battery, but I don't know that I want to spend the money for the proper battery.

I'll also mention that I checked the compression again after running and it's up to ~95psi, so it seems to be improving. I'm hoping maybe it will come up a bit more with some more operation.

I spent a bit of time on the other one also-mostly just cleaning as the blade brake/kill switch and really pretty much everything was gunked up. I realized the fuel like was torn, which explains why the whole thing is so filthy, and of course that's an easy one to fix.I spent some time working on it, although the recoil starter seems a bit "lazy" to wind back up. The ignition coil checks out in it. I'll hopefully tear it down a bit more in the next few days and see if I can find more going on with it.
Very nice. I definitely like the old 2 stroke lawn boys. I’m just not good with small engines so I can never get them to run correctly.

I’d have about 20 mins of mowing to do and spend about 30 trying to keep it running. Takes the fun out of lawn car real quick.
These seem to keep multiplying, and I'd better stop or I'll be in trouble.

I'll provide photos later today, but I picked up an 8235S on Monday.

This is a c. 1977(pre-compliance) 21" mower with a D601 engine(solid state ignition) and self propelled by the Capstan drive. It's a bit fussy to get started(need to figure out why) and I had to disable the self propel start interlock with a zip tie, but it does run and sounds great. Haven't actually tested the self propel yet as I couldn't get the lever to work when I had it running(fixed now with some PB blaster) but I'm sure it will work provided I get it adjusted correctly.

I love how lightweight this one is.
Way back in December I picked up another, and realized I never updated this. It's a 7232, a 1973-only push mower with a D600 engine and magnesium deck. It weighs almost nothing, which is a treat.

This one was actually bought from the original owner in a fairly well off area of St. Louis. It's obviously been used a lot, but has been maintained and the guy was only selling it because it wasn't running right and no one wanted to touch it. It would start but not stay running. It came with a side bag set-up(unfortunately the bag was a bit worse for wear and I found quickly the correct bags are difficult to find-I've since picked up a chute that lets me use both the original style and the slightly newer ones).

This one turned into quite a project. The starter was flaky and didn't always engage the flywheel, and the spring broke after my messing with it for a day or so. I put a new spring in, which is a little scary in and of itself(they're like a clock mainspring, and pack a punch) but still couldn't get reliable engagement. Finally I realized that one of the other springs-the one involved in kicking the gear out to engage the flywheel-was stretched and ultimately replacing it got it working perfectly.

This one has a metal carb-thankfully-that was in good shape.

I cleaned a bit pile of carbon out of the exhaust ports and muffler, but still couldn't get it to run more than a couple of seconds. I realized the someone had messed around with the carb adjustment screw probably trying to get it running right, so I set that to two turns out from all the way in(where the service manual says to go for a starting point). That at least got it running, but it surged terribly and just sounded bad.

These solid state coils-I think all of them actually up through the Duraforce era-have two "phases"-one that's supposed to operate below ~1000rpm for starting and I think sets the timing at just a couple of degrees BTDC(2º comes to mind). Above 1000rpms, it kicks out to about 20º BTDC. Sometimes they will get "stuck" in the start position, and of course will run terribly at speed with that little timing.

I ordered a coil-and somehow ended up with an F engine coil(I'll keep it in the spare parts even though it was horribly expensive). I pulled the one off my other D600 engine, though, and stuck it on. The engine started right up then ran great, especially after I dialed in the carb.

I want to give this one a full repaint and general clean-up but it's ready to mow come spring. I did order a full set of decals for it.


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Bunn, Excellent find. You are starting to amass quite a collecction. Enjoy, there are worse things that you could be investing in.

Thanks, you helped me get started down this dangerous road!

This has been a lot of fun, though, even if these newer acquisitions mean that I what I bought from you last year won't get used as much.