I still am going to play the naysayer. Heres some more on the subject:
1. Karts and Racing Lawnmowers are really a different proposition than a mini. There's a whale of a lot more room on them devices than a little mini frame. If the original pulley on the output shaft of the vertical engine is not below the bottom frame rails of a mini the engine will be rather high. If one gets very lucky and acquires a rightangle gearbox the heigth of the engine will still be rather high. Sure, as an old engineer said many years ago, "You can power a watch with a diesel engine, but that will likely limit it's mobility". Should we be worried about the center of gravity getting too high?
2. The website touted the fact that you can find lots of high horsepower vertical engines for short money. Looked at a 7 HP vertical motor today. The pitch diameter of the drive pulley appeared to be more than 5 inches. What's the plan to get the rear wheel RPM down to a useable level without a bulky device of some sort? We know that an 11 tooth sprocket [on a clutch] driving a 60 tooth rear wheel sprocket is the minimum reduction necessary to make the mini rideable [assumeing an 8 or 10 inch diameter tire]. That's approx 5.5 to 1 reduction. Again, I'm sure it can be done. Mentioned bevel gears in my 11/15 post. Be ready to build a purpose built gear box. Don't hope to find a ready made double ended gearbox small enough, rugged enough, and otherwise useable to fall in your lap. Here again we have a room problem. It would seem to me that not only would the ground clearance be impared, but also the bikes length would have to be increased.
3. Those big, wonderful, cheap, but under utilized vertical shaft engines also have a width problem when it comes to putting them in a mini.
4. Are you willing to keep the electric starter? How you gonna easily start it with a rope while sitting on the min bike? Tell ya what: Stand beside your mini bike an hold onto the throttle with one hand. Open it enough so that it will start and run. Then reach down with your other hand and yank the starter rope. Ever done that? You won't do it a second time without first putting the front wheel against the house. I have a three engine mini bike that requires an electric starter to light 'em up. Are you willing to carry a battery on your mini?
I'll be happy to be wrong regarding the desireability of big vertical shaft engines in old school mini bikes. Again...Yes it can be done, but it would be at best a conversation piece. Still seems to me that if you can't [or won't] turn the engine 90 degrees it's silly to comsider.
