"Bullnose" lawn tractor project

So I've got this ancient Craftsman riding mower. The deck was rusted out, and I removed it. I put a sleeve hitch on it and have currently been using it as a tractor. Problem is, the engine is shot. It ran and pretty good, but I had to put oil in it about every 30 minutes. Had pretty good power too. I pulled the engine and tore it down. It is a Briggs and Stratton 18hp opposed twin. Not too common these days. Most people I mention it to have never heard of one. Even my boss who has been working on small engine for 30+ years. Cylinders were pretty well worn, but they have cast iron sleeves, so boring oversize is not a big deal. A rebuild kit is about $280 with pistons and rods. Cost of machining is TBD. Problem is this: the crank appears to be unusable. The timing gear is held in place by a small key with a pin on the bottom that is pressed into the crank. Somehow, this has sheared off. Now, the timing gear does not have full travel, but does move back and forth a good bit. What doesn't make sense is that the engine was running great and had plenty of power. I also can see no way that I broke it while disassembling the engine. A replacement crank can be had, for about $275. Obviously that is not worthwhile. I can also get a used crank on ebay for about $15-$20. But the only ones available are not for my exact engine. I've read that they can be interchanged though. Other options: there is a 19.5hp opposed twin for sale on ebay, supposedly running, but needing gaskets. They want $350 for it, plus $50 shipping. Sounds great, as my full cost on rebuilding this engine may well be at or above that. One problem though: it's a vertical shaft model. From what I've read, converting one from vertical to horizontal is pretty straightforward, and I already have all the required parts. Just a matter of taking the sump and front cover, plus the correct oil slinger (these things are usually splash lubed, a few pressurized ones were made, but they aren't common.) As far as fixing the original crank, it may be possible. If the pin can be removed, a new one can be had and installed. Timing gear is shot, but I can get one for about $10. We'll see how it goes.

Wow!  That's quite the project!

I've not seen an engine like that, and I thought I've seen a lot of the small engines.  I'm going to tag Bill as he's been around a lot of the small engines and even has several.

I'd say get yourself a Predator Honda clone and be done with it.
I get it, you want something to screw around with.
I'm subscribed to follow the journey! 👍

I would, but it's not that easy. The drive to the rear wheels does not use a standard size pulley. The pulley attachment is also different. The Predators look great, and I have a 212cc that I adore, but the biggest they offer for a reasonable price is 15.8hp. It's also a pull cord start. The v-twin is $1000.

What model Craftsman tractor? I have a 1972 GTV16 that has a belt drive system that is interesting to say the least. Front belt layout looks like it was stolen from a Corvair, rear is fairly normal. Engine is a Briggs & Stratton 402417 16hp opposed flathead twin that is a horizontal shaft version.

I acquired a sleeve hitch for it after my former department manager bought it on eBay for his ST16. He found out the major difference between a Craftsman GT and ST, the frame width.

There are several groups for Craftsman or Sears tractors. As with many items Sears sold, they weren't made by Sears, but for them. Riding mowers and tractors had 3 main sources, Murray, for the cheap lines, MTD for the mid lines and AYP (American Yard Products) for the high end.

For Gary Lewis, here is another opposed twin powered tractor, a Ford YT16H:

It is a mid 80s GT18 supposedly a 1985 model. Here she is:





What's left of her anyway.

I think I'm starting to collect small engines. But only 4 cycle. I don't play well with 2 strokes.

Two strokes are good for weed wackers and chainsaws as they will run in any position.

Here are some pictures of a few of my engine collection:
Craftsman (Tecumseh) 10 hp cast iron engine.
  
Rare Tecumseh OHV V-twin, OV691EA. MTD wanted 18 HP, so Tecumseh sold then an 18 HP engine. It is actually more like 25 HP.
 
Here is my 16 HP Briggs & Stratton engine from my GTV16.
  

Just ordered the rebuild kit and another crank. Looks like this is going to cost $500 total, but that's still way cheaper than a new engine.

Wow!
That's a third of my axle!

You can download the IPL from Briggs & Stratton's website. Unfortunately, unlike Kohler, you can't get the service manual that way. I would recommend that be ordered so you have all the correct torque values.

The GT (Garden Tractor) models were initially equipt with Onan twins mounted sideways, flywheel on the left side, PTO on the right. I assume yours is configured that way but with the B&S engine. The GTV (Garden Tractor Varidrive) turned the engine 90° with the flywheel on the back of the engine and the PTO pulley on the front behind the grille.

I also have a sleeve hitch on mine and I built an adapter to mount a 2" hitch ball on the mechanism so I can spot or move my Aluma trailer or tow dolly with it.

I have the factory service manual. On this tractor, the pto is in the front, and the flywheel at the wheel. It has the six speed manual transaxle. Varidrive is a hydrostatic transaxle, correct?

No, varidrive is a variable ratio belt drive system. Front belt runs from the rear side (flywheel) of the engine, down to a pair of idlers, one a V style the other flat. From there it runs to a dual pulley with a floating center (originally may have had a spring to bias the center in one direction). The other side of the "variator" has the belt that drives the AYP 3 speed transaxle.

I will pretty well bet your has a hi-lo shift on that 3 speed transaxle.

Looks like you have a project on your hands
I dont know if you know of this web site or if they would have anything that may help you but give it a look over. https://www.mytractorforum.com/

I have a John Deere 445 garden tractor that I bought when I moved here in NC back in 2015.
It has a 22 hp V-Twin water cooled fuel injected Kawasaki.
Tractor has more options than my 81 F100 pickup LOL
The side covers were broken when I got it but got worst over time and last few years ran with out them.

Over the last month I have given it some much needed love.
Replaced the leaking front crank seal, the side covers,hood, grille and painted the tins.
I also upgraded the head lights with LED rock crawling lights in place of the 1156 bulbs.
Tractor looks brand new and dont want to use it and get it dirty LOL
Back when I first got it.


Dave ----

Yes, it has the hi-low lever on the "passenger" side. I'm looking at porting information on these engines. Seems like I just can't leave well enough alone!

That looks like a good place. The All Terrain Lawn Tractor Forum is where I'm getting most of my info. Them boys are crazy!

One of the lab supervisors at Newport News Shipbuilding built racing engines for a "stock" class using a B&S 5 hp single. He used a lot of the old Flathead tricks. He also designed and manufactured a boring setup for small engines, E-Z Bore Inc. www.ezbore.net

I used to wonder why people got into small engines because, how is 20hp exciting? But, you can build them SO CHEAP. They're also fun. Super easy to work and, plus you can pick them up and carry them around without a hoist. Well usually you can. When I picked up the Briggs twin, I tripped over a concrete block and fell flat on the ground. The engine landed on my knee. It's been purple and green for a while, but I'm walking normal again. Left a cool circle where the exhaust pipe hit.

When you are a kid you could get 3 to 5 hp motors for go karts and mini bikes.

I got into racing go karts that use 5 hp motors.
After blowing one up dad bought a new motor a HD rod and a gasket kit.
Pulled a new motor apart to install the HD rod, lighter flywheel and other safety gear and went racing again.

I would like to build a racing tractor, not a puller but a circle track one
In the fall some of the car shows also have tractors and the garden tractor pullers show up.
When 1 starts everyone goes to it.
Dave ----

Sounds like great fun. Got my rebuild kit today. Took a piston to my machinist. I went with 0.020 over pistons and 0.010 under rods. The aftermarket rods are supposed to be stronger. Still cast, but stronger. I'm going to try some porting of the block and heads. Interestingly, shaving the head and increasing compression is NOT recommended. If you look at the head, it makes sense. The flow from the bore to the valves is completely in the head. The block is flat (duh). If you shave the head, you are restricting flow from the valves to the combustion chamber. Bad flow with higher compression isn't good.