bgsengine wrote:Couldn't be - longer con rod with more throw on crank would change the stroke spec - as noted originally, both the 2.5 and the 3 HP have a 1.75" stroke, and stroke would be a function of the crank's throw... putting a longer rod in without changing throw would result in the piston poking through the head... and using a longer rod with shorter throw results in shorter stroke... Both engines also have the same displacement (8 CID) - What changes the HP output will be the same as what changes the Torque spec - Reducing the amount of air/fuel the engine is able to draw in, and altering its top no load governed speed.
My bad. I'm going from a 2.0HP to 3.0HP. Not 2.5HP.
The engine is a very old 1968 model 60100. I took the crankshaft, connecting rod, and piston out of an 80200 engine and put it in the 60100.
Same exact bore size, but the 3.0HP engine had a crank with a longer throw. That tells me the crankcases are identical.
I installed a Magnetron ignition coil kit and a chrome ring kit that consisted of 8 piston rings total. The cylinder bore was only worn .001.
Still have the engine today. It's sitting on a McLane edger. It burns cleaner than a new engine does. Great little engine.