Complete agreement with that statement. The driver/driven need to be facing in opposite directions on the 40 series, and the backplate units I've seen have the driven on backwards, so it acts like Denny said. Here's an example of that, with the driven on backwards................I can not recommend it though because there is an alignment issue at high speed. Some people say it does not matter. I say it does by reducing belt life and uses extra power making it less efficient.
Correct, and thanks for the reread to see what I said. Now, you just gave me an insight that I'd either overlooked or forgotten about. It might very well be that the shaft adapter I saw before did indeed have both an internal keyway and an external keystock (NOT 2 keyways).I would think you would need both an internal and external keyway to facilitate the drive shaft
Maybe for some, but not for me. I would never want to get more than walking distance from shelter (home base) with that setup.the 40 series with it's back plate is the next way to go ?????
OK bullies...I'm thinking about a jack shaft.....
This time I consider that a compliment! Thank you for being smart enough to listen!OK bullies...I'm thinking about a jack shaft.....How do you determine distance from crank shaft to jack shaft so the belt will fit ?

That's all correct, but I forgot to mention..............You'll be needing to adjust the motor back/forth in a slotted mount for chain tensioning. You should mount your jackshaft on a plate along with the motor, so it moves back/forth with the motor. Otherwise, the motor will have to stay in one place, and chain tensioning will have to be done with some kind of separate chain tensioner. See homemade tensioner with an idler sprocket for secondary chain in pics below.................You can put your jackshaft anywhere that one of those c-c measurements allows for
My Yerf Dog 3203 has a separate jackshaft mount bracket, that butts up against the engine, and has elongated slots in the same chassis mounted engine mount plate. You loosen up the engine mount bolts and the jackshaft mount bolts. Move the engine to adjust the chain and tighten the engine mount bolts. Slide the jackshaft bracket up tight against the engine and tighten the bracket mount bolts. Centerline to Centerline is maintained this way. At least, that is what I have been doing.That's all correct, but I forgot to mention..............You'll be needing to adjust the motor back/forth in a slotted mount for chain tensioning. You should mount your jackshaft on a plate along with the motor, so it moves back/forth with the motor. Otherwise, the motor will have to stay in one place, and chain tensioning will have to be done with some kind of separate chain tensioner. See homemade tensioner with an idler sprocket for secondary chain in pics below.................