HRM 1.4 hp Factor & Vibration

Hey this one's for all MB hp factoring naysayers out there.

The 1.40 hp per cubic inch factor for a modified drag-racing engine, (2-strokes qualify), is real.
Just ask the authority, Hot Rod Magazine.
My only mistake was not having the HRM quote handy when I posted in the MB forum.
I said the 1.40 factor for each successive modification would apply to any 2-stroke motor starting from it's manufacturer's base hp rating. OK so that's stretching it a bit.
Why? Because no-one knows the 66cc HT motor's actual base horsepower rating.
Example; some retailers are saying the PK-80 generates 2.75 hp bone stock.

Thus a stock (low rated) 48cc engine making 1.6 hp @ 5,000 rpm x 1.40 would equate to 5.88 horsepower. [4.2 cu. in. x 1.4 factor] ... if modified.
I was pretty durn'd close using the old desert racer "rough method" figuring on a scratch pad. My simple method compared to complex VE vs. rpm, etc. was declared invalid.
Damn! then why does the seat-of-the-pants 1.4 hp per cu. in. factoring method work, come rain or shine, and served us well, in planning engine mods, for decades?

Show me any stock stroke, ported, piped, up-carbed, China two stroke of "66cc" (47mm bore x 40mm stroke) and it will make a maximum of 8.5 horsepower (without engine coatings). Got a real printed dynamometer test reading for that motor - signed!?
If you possess such a motor then you need to apply to a GP motorcycle racing team right away.

Killer Hornets
The real practical limit for using any motorized bicycle engine's horsepower is vibration.
How much vibration can you stand while riding over 25 mph?
At 23-24 mph my 66cc balanced PK-80 buzzed the ole Cranbrook frame like a million hornets on steroids. Everything on the bike was vibrating - hard!
The other input is road-related vibration. With poorly maintained streets rough as a cobb, a motorized bike MB needs some suspension.
Wally world bikes like Huffy, Bike Path and Micargi can develop frame stress cracks from metal fatigue.
Note to self - get thee a better, more rugged, high tensile steel bike frame asap.
Like the Giant Stiletto, Schwinn Spoiler chopper bikes. Bring a fat check.
These fancy dudes (bikes) are pricey!

So where are really strong, affordable MB frames to be found? Read on.

I'll stick with the all steel Raleigh M-80 MTB frame from the late 1990s, built to similar dimensions and specs as a vintage cro-mo Trek 830.
Both work like the proverbial blacksmith's anvil.

My cro-moly Trek 830

Stout is the word.