First build advice

[Primut]

So I've been researching building a motorized bicycle off and on for a while now, and my vision has changed several times as I read and learn, from my original plan to motorize a Micargi Sluggo SS (which I quickly found out KC Vale had built a great example of, and pined after for a while), to a more chopper type bike, and then swung hard away from style driven back towards practicality, seriously considered a phatmoto(until I realized who was behind it) then I bought a mongoose mack after some rough scaling from photos and trig to see if there was room for a midframe mount with a 79cc pretendator© kit, then winter. Now that it's past the worst (I hope) I want to get the ball rolling, but instead of a kit I want to use the kits' parts lists to piece it together myself with respectable quality components, but first I'd like to hear the voice of experience on a few points. First of all I had been caveman-thinking that I need a 79cc(legal limit here in OK) to haul me up the hills around here and achieve respectable top end, but A)I've seen several comments around opining that a 49cc with the magic gearing setup will outshine even an ungoverned 79cc in either or both aspects & B)Taking into account what my idea of and the general consensus on what a respectable speed is, I realized that legality isn't as important to me as the appearance of legality, and I swear it was a freak tailwind officer. So now I'm back to the beginning wondering what displacement will fit the frame and pull 180-190# of meat up a moderate hill and still attain 35+ mph (obviously + is better . . . to me anyhow), can occasionally handle grocery/human cargo, and what gearing is required to get there with it. Also wondering what upgraded vs kit parts I should be aware of such as spring tensioners vs 1 clamping bolt fixed tensioners, properly durable chain etc. I'm thinking shift kit from sbp, but if i decide to make that a separate add on later I know the thought of a pineapple bushing repulses me no matter how many people attest to their suitability when installed correctly, so I'd be looking at something like this(although tooth count and supplier/retailer are still up in the air): https://www.amazon.com/CDHPOWER-Ada...torized-Bicycle/dp/B06XKJT29J?ref_=ast_bbp_dp

I realize that at the very least mounting brackets will need modified or fabricated due to the nonstandard downtube shape. I am a machinist and work in a sheet metal fabrication shop so this does not concern me, but it wouldn't break my heart to be able to afford to turn the mack into a parts donor for a tank frame either so I'll be checking sizes to see how much would be transferrable sometime this weekend.
Also thinking of adding a wiring harness later for a small battery/electric ignition/lights if that has any relevance. Looking to put another $700 or so into it, maybe as much as $850 if it really ties the room together, man. Thx for reading the novel and any insights

 

[darwin]

Seems you know a lot about MAB's. You just need to decide exactly what you want. Once you've made a decision you know what to do. Welcome to the forum and good luck!

 

[HumanPerson]

I like your hair darwin

 

[Deleted member 26224]

79cc 4stroke single speed 10 or 11:1 26”

 

[Old Busted Hotness]

You've got the right idea with piecing it together instead of buying a kit. I started with a kit, and two years later the only thing I had left of it was the tank and throttle handle. Everything else proved to be substandard. Build it right and it'll be a joy to ride.

One bit of advice I'll offer: Before you start, ride the bike down a steep hill, see if you can get it up to your target speed and see how it handles. A bike that feels fine at pedalling speeds can feel twitchy at 25-30 mph and above. I like a cruiser frame with a long wheelbase, but your mileage may vary.

 

[Wrench]

Howzit Primut, Welcome
Can't wait to see what ya come up with. Keep us posted

 

[darwin]

I like your hair darwin

Thanks, just happened to get back from the beauty salon.

 

[Primut]

So I've decided I'm going to go ahead and get a tank frame, the 3.4L from CDHPower, and it's going to be a shifter from the start. I don't want to bother with buying engine mounting brackets or a shift kit with a jackshaft bracket, I'm just going to buy the frame/79cc pred(nix the governor)/intake/throttle linkage/exhaust and fabricate as much of the drivetrain and brackets as I can once I have the rest to mock it up and fit it together. No access to a lathe right now, but material/mill/shear/punch/brake/rolls/weld are at hand, so that'll cover a lot. I also don't have access to a gear shaper or broach so I'll have to buy all pinions/sprockets. Funny enough, I used to make gears for a living(for PTO products) but I know about zero about gearing as far as selecting the right reduction ratio for this or any application, I just made them. I want to reuse the mag wheels from my mack, but I don't know if the cassette it came with is suitable for this, where to start on replacing it of not, and anything at all about what reduction I'll need at which point in the drive train to both climb hills and satisfy my inner speed junkie. Since the gearing will dictate location and amount of space needed there for components, I can't start any fabrication without risking shooting myself in the foot and having to scrap and refab components due to poor planning, and the less time I spend at work on a gov't job the better. So opinions on/upgrades to the cassette? Any starting point on drivetrain gearing or link to a breakdown on all the math and how it applies to a motored shifter bike with a cassette or reasonable upgrade to it? I'm not trying to catch shrapnel from a cassette grenading on me, but I'd prefer pedaling to be completely optional. I've looked around, but all I've seen is opinions of people who know gearing meant for others who do, which I don't follow, or for different enough drivetrains that I doubt it would be wise to try to base mine on it.

 

[Just_Doin'_My_Own_Thing]

You've got the right idea with piecing it together instead of buying a kit. I started with a kit, and two years later the only thing I had left of it was the tank and throttle handle. Everything else proved to be substandard. Build it right and it'll be a joy to ride.

Its problably cheaper in the long run to spend more money on quality parts upfront than to replace the cheap parts as they fail, not to mention you'll spend less time trying to make the cheap parts fit on the bike.

Anyway, sounds like a cool build, I wish I had the paitence to put the right parts on the first time, couldve saved me some heartache.

Oh we, live and learn

 

[Just_Doin'_My_Own_Thing]

If you wanna know about gearing, check out some of the sticky threads in transmission/drivetrain