Here's where I fall on the 4-stroke kit question....
If you keep the oil where it belongs and clean, if you keep the air-filter and intake mixture clean, if you stay on top of the valve lash and don't over-rev the crap of it, replacing a major part like a piston shouldn't even be an issue. If something major like that fails, then the motor gets replaced. It was a bad motor.
The 142F vs 144F question? That will depend on the individual buyer. Some people will pony out $$$ for a barely-quantifiable increase in performance and/or durability because it strokes their ego and just makes them feel good. I say, let 'em.... it's not MY money they're spending.
I think you know where I'm heading with this. I don't personally feel it's worth the premium vendors are charging for the difference in performance between the two. The piston replacement issue, I addressed above. It has been pointed out that the clutch/reduction area is an issue because of the differing shaft ends, and that could be a Thing, because it's a wear point.
It makes me wonder if the 144F is just a natural evolution... Sort of like the Small Block Ford of the early 60's... born as 221, but the architecture was capable of being produced as a 289 (without a stroke change).... Pretty much the same engine for most all purposes, but a 25% increase in displacement. Sort of like a 49cc being punched out to 64cc! It's just odd. The arbitrary law of 50cc or less make the 49cc seem logical. The 53cc is just.... ? ? ?
Maybe it's like the Honda Clone Thing that started a few years ago.... Honda did the 196cc GX200, a very nice, smooth, torquey package that fit onto a lot of things. It got cloned by less expensive knock-offs, then Honda leaned on the clones in court for copying their design, so the clones altered their designs, but pretty much retained the Honda's good basic design. Some, like Harbor Freight, obviously saw an opportunity to have the perceived advantage of a few extra CCs and went from 196 to 212. Guess what? 196cc to 212cc is the same percentage as 49cc to 53cc. I think with such small incremental increases, that it's pretty much a Marketing Perception Thing.
And now I apologize for droning on with my opinions. Sorry!
