05-15-2021, 09:57 PM
(This post was last modified: 05-15-2021, 09:59 PM by Terry Bentley.)
They are great chainsaw motors. I have good dozen of them. Sears sold David Bradley model chainsaws. The PP81 is a heavy monster of a saw.
Montgomery Wards sold a line of saws using the Power products engines. They were seriously detuned by using that small Tecumseh diaphragm carburetor found on 2.5 and 3 hp lawnmower and mini-bike engines. If you get a decent aftermarket intake using a pyramid reed and a newer model Tillotson carburetor, that motor will surprise you.
I made billet heads for a few of my project engines. Hard to find originals. You can also rotate the cylinder 90 degrees, so exhaust shoots down instead out the side. The intake ports are fed thru holes in the piston skirts on some models. You can case feed the intakes with some grinding and spare time.
The early models, including the Ah-81 are horribly out of ba1ance. You can add counterweights to crankshaft or grind off a lot of dead weight around the rod end of crank.
For pistons, bore out the cylinder +0.020 and use the Westbend 820. The Westbend rod is another good swap. It is stronger than the PP rod.
A pair of these engines develops a ton of torque. With some simple mods, they can be made fairly fast. Just keep the rpms low and you wont be blowing them up every time they get run.
The flywheels are huge and need to be cut way down. Most of the fins can be removed completely. You can shorten the square style shrouds a lot to better fit the cut down flywheels. The flywheels were known to explode, so a reinforcing plate welded inside keeps them from breaking.
Otherwise a fairly fun motor to play with. When using one of the chainsaws, my arms would stay vibrating for about an hour after I am done cutting wood. I can even feel it in my teeth.
Montgomery Wards sold a line of saws using the Power products engines. They were seriously detuned by using that small Tecumseh diaphragm carburetor found on 2.5 and 3 hp lawnmower and mini-bike engines. If you get a decent aftermarket intake using a pyramid reed and a newer model Tillotson carburetor, that motor will surprise you.
I made billet heads for a few of my project engines. Hard to find originals. You can also rotate the cylinder 90 degrees, so exhaust shoots down instead out the side. The intake ports are fed thru holes in the piston skirts on some models. You can case feed the intakes with some grinding and spare time.
The early models, including the Ah-81 are horribly out of ba1ance. You can add counterweights to crankshaft or grind off a lot of dead weight around the rod end of crank.
For pistons, bore out the cylinder +0.020 and use the Westbend 820. The Westbend rod is another good swap. It is stronger than the PP rod.
A pair of these engines develops a ton of torque. With some simple mods, they can be made fairly fast. Just keep the rpms low and you wont be blowing them up every time they get run.
The flywheels are huge and need to be cut way down. Most of the fins can be removed completely. You can shorten the square style shrouds a lot to better fit the cut down flywheels. The flywheels were known to explode, so a reinforcing plate welded inside keeps them from breaking.
Otherwise a fairly fun motor to play with. When using one of the chainsaws, my arms would stay vibrating for about an hour after I am done cutting wood. I can even feel it in my teeth.