Can you put a larger engine in a Bolens tractor

Kurt, if you do decide to put a bigger motor in, buy an larger version of the motor you have in there. So say your machine was made in 68 with a 12 HP briggs, buy a 16 HP briggs made the same year. The cast irons were more durable, you can't beat them, that's why these old machines still run now. I had a Simplicity 700 and that was only 8HP and it would bog to god knows where, if I did that on my new simplicity with 14HP kohler, she'd die in a second. Just a thought.

P.S. attached is a picture of my old "might might"

If your 12 is running good, what could you possibly need any more power for? I was clearing snow with my Bolens Husky 600 with a 6 hp B&S and didn't find anything I couldn't move with a push or two (well, some of them needed 5 or 6). This is the smallest and lightest of the Bolens Tube Frame models and doesn't even have the posi-traction rear end.

If you have your weights and chains set up properly you can move a mountain with these things. I would add your weight first, before you go through the trouble of trying to swap in another motor. First is the expense of another good engine, second is the aggrivation of trying to get everything lined up and fitting under the hood.

I am guessing you have an HH120, and that is just a BEAR of a motor - you will be sorely dissapointed if you put a modern 16-18-20hp engine in its place. These new motors may have higher hp, but cannot compare with the torque produced by the older cast iron single cylinder engines made by all the big producers (Kohler, Wisconsin, Tecumseh, and even Briggs & Stratton). Torque is what will get the work done.

If you are bound and determined that a motor swap is what you are after, give me some more details about the exact model tractor you have and I can look through my information and tell you the what will work. If you have a 1220 or G-12 it is a Tube Frame and the largest engine that bolens put into this series with the gear drive was a 15hp Tecumseh overhead valve engine. This conversion will require a new hood as the OHV models had a bump out so the engine would fit.

I also live in MI and would can help you get your tractor set up if you would like, where abouts do you live? Let me know some more details and I will do what I can to get you where you want to be.

Ron H.

Kurt,
I'll admit 18 inches is a lot of snow, but usually you will spin the tires or slide sideways before you will stall the engine. The real issue is traction not only for your drive wheels, but also for the front tires.

I have attached a picture (hope it works) showing my setup from last year. Look at the weight box on the back. I purchased it from JohhnyProducts (http://www.johnnyproducts.com/) and it is just the ticket. You can also see the front wheel weights - they really help keep the front wheels from sliding sideways (you can also buy chains for the fronts if needed).

With this tractor (8 hp engine) I was able to push wet slushy snow well over the top of the blade and move it up a snow bank to pile it. The trick is to find the right gear so that you have pretty good forward speed. I think I was using HI range and 2nd gear most of the time. You want the blade angled all the way to one side and be moving fast enough to have it over come the 'stiction' to slide off to the side (apply a little paste wax if you want). If you keep the blade straight you will run out of traction much quicker.

Now about your comment about torque being directly proportional to rpm. I can't argue with the math, but the torque peak hits at a different rpm range than the hp peak. Maybe somebody will jump in and give the technical details, but the real issue is what happens when you put a load on the engine. Will the governor be able to react and keep the engine in it's power band or will it try and die out so you have to push in the clutch to keep it running. These old single cylinder engines have a long stroke and can recover very well from having a sudden load applied. The newer engines with the higher hp ratings are fine with a steady load such as a mower would apply, but as soon as you start apply a variable load the rpm drops off rapidly and they fall right out of their power band.

The real issue is: Are you stalling the engine? If not more HP will not help you one bit. If you are spinning the tires then increasing traction via weight and chains is the only solution. If you find you are stalling out an HH120, you are probably taking too big of a bite at once and you might try a different technique. That engine on that tractor should do you just fine.

Sorry to sound so preachy, I really only want to provide good sound advice so that you get the most bang for your buck.

Drop me a line anytime,
Ron H.

• Rear Weight Box for Bolens Tube Frames by JohnnyProducts

She aint pretty but that 16hp twin sure out runs the old 8hp it came stock with. Used the existing mounting holes which let the motor sit somewhat cattywampus, but it's been a runner season after season.