I don't ride for exercise, I ride either to test or get somewhere in comfort, especially in summer.
The LAST thing I want to be doing is exerting any effort when it's 110F outside!
I'm building an in-frame bike because I want it to be strong and fast and handle well.
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2-stroke engine kit right?
Strong AND Fast simply can't happen with a fixed single gear ratio.
If you want great low end and high speeds install the engine with a shift kit and get a good bike with gears.
The 26" Fito Modea 7-speed is a nice nimble bike.
7-speed with 3" wide tires on 24" rims and dual disc brakes.
~$350 from BikeBuyers.com
The shift kit ~$200 from SickBikeParts.com
You want a dual pull brake lever and front mount from SBP as well.
~$30 for those parts.
Though 7-speed derailleurs are common and cheap, I find them to be overkill gear steps and literally the 'weak link' in the system.
Though it's easy to learn how to shift one properly the thin chain is an issue if you miss-shift, it's pretty easy to snap that chain or a sprocket tooth.
I don't use all 7 gears either, that is for human power so I usually just shift between the even numbered gears as chain angle gets extreme in 1st and 7th.
I'll take an internal shifter every time.
I replaced the 7-speed hub with a Strumey-Archer 3-speed with disc mount on this build.
That gives you Low, Drive, and Overdrive for your engine.
You can use HD 410 single speed chain and it's always in alignment so not prone to wear or breaking like 7-speed chain and sprockets under engine power.
I don't like the straight triple forks on the Fito either.
The extra thick 3" tires take some of the road out of the ride, I put an XCM suspension fork with disc mount on this build.
~$85.
Pop a wheelie in Low and pass 45mph in Overdrive.
As for all the friction drive stuff...
Jezz guys, he has a 2-stroke center mount engine.
It requires a bump start and never been designed for rear wheel friction mount so just silly to bring up in this topic don't ya think?