Looks like an engine swap many years ago. The correct engine for that one would be a C-70.

 

It looks like they put a bricktop C engine on and rotated it 90 degrees.

 

The engine is turned 90 degrees due to the muffler plates for those mowers, along with the Buttercups, have the jugs pointing forward. The C series engines for those mowers have tear drop shaped shrouds, which are completely different than the Bricktop shrouds. Those mowers are very cool!

 

Looks to be a cool project many years ago for someone. The original engine (C-70) only had a cylinder bore of 1-15/16" with 4.43 cu. in. displacement. If the C engine brick that was transplanted is a large bore, ie. C-18, or C-19, then the displacement was increased to 6.65 cu. in. making a bunch more torque than the original engine. Someone was building a hot rod 18 incher! Can you see the cylinder fin data tag to see what C series engine that is? I also like the 1/4" or so yellow pin stripping. I have a feeling there is some history in that machine. If only the mowers could talk?

Edit: After flipping through the manuals (on-line), I noticed that the top dawg in displacement for all C and D series engines goes to the one and only, 1967 model 3002 Buttercup with the C-78 engine. The piston diameter for the C-78 is listed as 2.438 in., while the standard large bore C or D is listed as 2.37 in. No wonder everyone wants one of those. While Carroll Shelby was building monster Mustangs and Cobras, the OMC guys were building a sleeper mower in the little 18inch 1967 Buttercup. According to the manual it's a one year only deal. Sure would like to hear some background info on that. It's also showing some contradiction in the cylinder bore and piston diameter, so not real sure just how big of a piston it really is on a C-78, but could very well be the biggest of all those large bore C's and D's.

 

hello all
to share with all you lawn-boy guys the first large bore C-series 1962 7251 the C-18 engine
same size bore also 1962 model 8220 auto mower piston part number 604099 also to share
as Rex has said 1967 3002 large bore C-series engine also 1968 and 1969 also models 3002
last buttercup mower 1970 3003 engine C-79 this info come from my lawn-boy mower and parts
manual it also has info on the iron horse mowers this manual came from my grandfather who was a
lawn-boy dealer i learned to work on lawn-boy mowers from him i always like to help other lawn-boy
users out also to share just got a 1965 7254 it was shipped to in pieces the housing is right now at a
friends body shop for paint and already have engine but there is also engine to so will have spare when done
your lawn-boy friend Scott

 

Thanks for all the intel. An engine swap definitely sounds like something my grandfather might do--not necessarily to build a hot rod, but to utilize whatever might have been available. He was a mechanically-inclined and resourceful guy. I'll have to retrieve the mower and start peeling the layers to find out exactly what he did. I'll be sure to post my findings.

 

Good luck getting it up and running! I look forward to seeing/hearing about your progress -- and I know others here will as well.

 

Anything with an engine is interesting. Doubly so, if it is old and hasn't run in 40 yrs. Please update your progress. Whenever I see a really old 2 stroke taken apart and laid out on a table, I marvel at how few parts there are. I've never had to tear a 2 stroke down. All mine run.

 

Brought the mower home today and started scraping off decades of gooey crud. The engine is a C-12. The serial number on the shroud is 1549063. I believe this would have originally been on a 1957 7100, yes?

My plan is to clean the carburetor and fuel tank and try to get it running again. Since it's already a franken-mower, I don't see much point in a painstaking restoration. When I do get it back together, what ratio of fuel/oil should I use? Anything else to look out for? Thanks in advance.

 

Alright a C-12! Yes I think you are very close to the model number of the mower the engine came off of. It's from any of these listed here according to the Lawnboy model number quick reference table: 1956 5000/7000, 1957 5100/7100, 1958 5100/7100. Old lawnboy (Bill) might be able to narrow it down even further with that serial number. He is really good at deciphering those serial numbers and coming up with an exact date of manufacture. Those S/N# always throw me for a loop, like yours starts with a "1" so that should mean 1961, but no C-12's were used in 1961.

I almost forgot to answer the question about fuel mix for these. That will be listed as a 16 to 1 fuel/oil mix. Basically any of these stock Lawnboys made prior to 1970 will be 16 to 1 ratio.

It shouldn't be that hard to get it back up and running. I just have a feeling that your grandfather was pretty good about maintaining his equipment. I think you have the link to the manuals, but just in case I'll post it again below. It doesn't have a lot of the C series details, but then again the old C series is very similar to the D series other than the ignition setup, it has a choke instead aprimer, and no spark advance for easy starting. It has a very small section that covers the major differences. Take plenty of pictures all throughout! Take notes too. The C series is a bit more challenging getting the ignition system put back together correctly than the others, so this is where good pics will come in very handy. Okay keep us posted.

https://lookup3.toro.com/ttcGateway/Acrobat/manuals/lball.html

 

The engine had both spark and compression, so I'm optimistic that a quick cleanup of the carb and fuel system will do the trick. So far, my new parts list consists of new carb gaskets, a new air filter, new rubber fuel line, and a new fuel shutoff valve (old one did not have the strainer and the wing nut on the external side was missing). The spark plug is an Autolite 238 that showed normal wear. I didn't find this particular plug with Google search. What are other folks using on C-12s?

Thanks again. I'll put up some more pics of my progress when I get a chance.

 

So far, my new parts list consists of new carb gaskets, a new air filter, new rubber fuel line, and a new fuel shutoff valve (old one did not have the strainer and the wing nut on the external side was missing).

Even though it had spark, I'll be adding a coil to the new parts list . . .

Everything should arrive early next week. That will give me time to continue cleaning, while shooting for a July 4 weekend re-assembly.

 

Nice
Sounds like it shouldn’t take much to get it going
A CJ14 plug should work good for that motor


Sent from my iPhone using Tapatalk

 

GRreat! I love stories like this. Thanks so much for the follow up.

 

I'm amazed that it was still sparking like that. Durable machines, these old 'Boys!

 

Almost ready for reassembly. I plan on starting a new thread with more details on the rehab process. In the meantime, here's a Google album with some pics to date:

https://photos.app.goo.gl/S2vkvDzPt59N1x2Y6

 

Started on some reassembly last night, and did a spark check before putting everything back together. I'm getting spark, but only inconsistently. I've set and reset the air gap on the coil, re-gapped the points and plug and double-checked all connections. My best guess is that the wear block on the breaker may be too worn, causing a short to the crankshaft. New point set is on the way.

 

Being the impatient SOB that I am, I used a little JB weld to build up the wear block while waiting for a new point set to arrive. The spark improved, so I went ahead and completed reassembly with the exception of the governor rod and the blade. I sprayed a little starter fluid into the carb, set the choke and . . .

she turned over and puttered a bit until the starting fluid petered out.

Here she is, waiting for me to mix up some 16:1. More to come . . .

 

Everything is now about 95% complete, but not without a little adventure. Still need to install the governor rod and install the new point set when it arrives. In the meantime, I put everything else back together, added some fresh 16:1 fuel mix and tried to start it. The pull cord was binding, so I removed the pull cord assembly and used a drill to get it going. Fired up pretty readily and settled into a nice idle.

Except . . . I didn't notice that the top nut on the crankshaft had loosened as a result of the drill-start . . . which in turn caused the flywheel pulley to loosen . . . which in turn caused the starter pin and spring to fly off somewhere in the grass. :bonk:

I broke out a Harbor Freight magnetic tool holder and swept the yard. Surprisingly, it picked up the spring. No such luck with the pin.

However, I did happen to have some steel rod on hand that just happened to be the right diameter. Seems fitting that I had to MacGyver the last piece on my grandfather's mower that itself is a marriage of two mowers. Here's a video of it firing up. I ended up mowing my whole yard.

 

Very nice! Thanks for sharing! That mower has nice patina and character. I'm usually one to lean toward a total restore, but with that being your grandfather's project I think I'd just leave it as is.

 

That's how I looked at it. If I had been presented with an engine that matched the deck, I would have gone in for a full restore. If it had no family connection, I likely would have parted it out.

As it is, I ended up spending about $60 for new parts replacing only what was necessary (not counting massive quantities of cleaning supplies). To put that in perspective, I acquired two operational Hondas (HR214 push and HR215 self-propelled) for the combined sum of $50 this summer. This was not a fiscally responsible project, but I sure loved every minute of it. (Except maybe losing the starter pin and spring . . . )

 

Short post-script . . .

In looking back over some of the pictures, I noticed an interesting pattern cast into the bottom of the deck . . .

I took everything apart again, and lo and behold, the false mounting holes line up perfectly with the muffler plate if you rotate the muffler plate 90 degrees to have the brick top face frontwards . . .

So, after a quick grind and drill session, we're now reassembled with the motor facing the way it should.

 

Looks fantastic! Great job, I think your grandfather would approve.