Motorized Bike Laws, Builds, and Musings

Things are beginning to look like I’m adding my first two-stroke to the fleet. Actually probably two two-strokes. A few days ago I posted someone selling a Craigslist motorized bike for $400. You guys gave me some really sound advice but...

The seed has been planted.

Summary of comments from the last post:

  1. Local laws vary significantly and probably only allow 50cc bikes
  2. For $400 you can get a new one of those
  3. Why not get a motorcycle/ scooter?

All really good points and they’ve led to a fair amount of research.

Let’s start with “why?”

I mean... why not?

No but seriously, I live in a city with both terrible roads and terrible drivers. I have absolutely no desire to own or operate a motorcycle on these roads. I have, however, ridden a bike and somewhat enjoyed it. Ok... I used to enjoy it. When my bike was stolen it was really more of a relief than anything.


But I digress. The real reason “why” is because it is a relatively cheap (~$350) novelty. A laugh. A think you play around with for a year and eventually sell on Craigslist.

Nothing more.

My rental car next month is going to cost more than this thing and be way less entertaining, if quite a bit more useful.

So yeah, I don’t want a scooter or a motorcycle because those are motor vehicles. A motorized bicycle is a bicycle.

What to buy?

Well you guys were right. $400 is about what a new kit costs, so I think we’re doing that. And I say “we” because I’m working on the boyfriend to get one too... because it won’t be any fun I don’t have anyone too tool around with.


So yeah... tl;dr is I’m looking at getting an 80cc bike motor kit. Or a 50cc kit. The 80cc kit is $40 more but I’m... not sure I want to go that fast?


Bike-wise things are getting a little complicated, as per my usual. Originally I was planning on buying a complete kit from BikeBerry. The all-in-one kit seemed like a sure thing to make sure the bike was easy to build exceeeeept...

Well I noticed the Bike Betty kit didn’t come with mud guards, a parcel shelf, or external brakes. In fact, I can’t find any single-speed bike that has cable brakes, only coaster brakes...


Multigear bikes do, but those are likely against the law to motorize. (See below)

Well shit... down the rabbit hole we go!

Ok so it looks like my option is to add brakes to a single speed bike or to convert a multi-speed bike into a fixed gear bike. The former seems easier, and Amazon sells a kit for about $40 once you include the single brake lever.


I know I want a chain guard and a parcel shelf, and I think mud guards would be nice too. I know they can be a liability, but water being sprayed all over your everything is also a great way to ruin a ride.


So right now I’m looking at something like above,and add v-brakes to it. (And removing the basket and cup holder because... no. That’s too much, even for me.) Seems like that way I can get the best of both worlds and, weirdly, save a little money over buying the complete kit.

I’ll also look into essentially reassembling and re-greasing everything, because apparently “department store” bikes are known to explode upon use, even if not motorized. No seriously, the internet told me that if you ride one for more than 50 feet the welds will crack, the wheels will fall off, the hubs will seize, and 15 baby pandas will die.


The internet tends to worry. A lot. (HI INTERNET!)

Anyway, the only day 1 engine upgrades I’m looking at is adding a bigger muffler. I want this thing to be quite.


The plan is to buy two at the same time and build them simultaneously both for accountability and ease. It would make more sense to buy one, try it, and then build another but... I doubt we’ll do that.

Legal Stuff

This, as you might expect, has been where the bulk of my research has taken place. What I really wanted to know is, for my state, what type of motorized bikes are allowed, where, and what are the restrictions.


It appears the primary law governing this is Oklahoma Title 47, which covers all “Motor Vehicles” which, oddly, includes bicycles, electric-assisted bikes, and motorized bicycles.


What, legally, is constitutes a “motorized bicycle”?

According to Oklahoma Title 47, Chapter 1, Section 1-104, “Definitions of Words and Phrases - Bicycle, Electric-Assisted Bicycle, and Motorized Bicycle” a motorized bicycle is a bicycle that meets the following criteria:

  1. Fully operative pedals for propulsion by human power;
  2. A power drive system that functions directly or automatically without clutching or shifting by the operator after the drive system is engaged; and
  3. A combustion engine with a piston or rotor displacement of eighty (80 cu cm) cubic centimeters or less, regardless of the number of chambers in the engine, which is capable of propelling the bicycle at a maximum design speed of not more than thirty-five (35) miles per hour on level ground.

Point 1 is fairly straightforward. Two and three are where things get questionable.

The first part where the drive mechanism must operate “directly or automatically without clutching makes sense is a little confusing. Every one of these I’ve seen uses an centrifugal clutch, so no problems there. Most kits seem to come with a cable operated clutch. I’m not sure if these qualify? I mean... you engage the clutch to engage drive, but no additional clutching is required afterwards.  I’m not so sure on this one.  A centrifugal clutch would solve this, so I’m going to investigate those.


The 2nd part is a little weirder, as it seems to say the operator must not be able to shift? Have the ability to shift?  The way I read #2, and as far as I can tell others read it, is that the bike needs an “automatic transmission”. This explains why most bikes and bike kits I see are fitted to fixed gear bicycles.

Weirdly, for legalize this doesn’t seem to be very tightly written. I could see an argument made that could allow a multi-speed bike... but if nothing else I having gears would quickly allow you to violate #3.


Point #3 is pretty straightforward too. No more than 80cc, no faster than 35 MPH. Not sure how they police the 35 MPH thing aside from getting caught speeding down the freeway at 100 MPH but... here we are.


I, weirdly, haven’t found much other than hearsay about this. Allegedly, according to Motorized Bicycle HQ, motorized bicycles are required to be titled, tagged, and registered.


Additionally they say you’re required to have a driver’s licence and be over 16... but I also can’t find that in the law.

The latter doesn’t matter because I already have one of those. The former... I guess I’ll visit the tag agency and see what they say? Or just wing it.


Where can you ride?

Another mildly unclear point. Which is to say all of the laws in Title 47 I’ve read refer to bicycles and motorized bicycles as the same thing. Actually that is explict in Section 1-104:

As used in this title, the term “bicycle” shall include tricycles, quadcycles, or similar human-powered devices, electric-assisted bicycles, and motorized bicycles unless otherwise specifically indicated


Reading through the bike path rules there is nothing explicitly against running a motorized bicycle on a bike path or in a bike lane... which is... surprising. That said, zoom in on a bike trail near my house and you get a more predictable, if a little confusing, indication of what is allowed.


I’ve always taken that to mean “don’t drive your car or motorcycle on here, you idiot” but I could also see it meaning “don’t drive your stupid weedeater bike on here, you boob”. I mean, if I were a cyclist I wouldn’t want one of these monstrosities on my trail.

I’m inclined to think the former, not the latter, but the plan is to not abuse that. There are a couple of areas where the bike trails avoid some nasty traffic crossings and roads, so I think absolutely use them there.


Other requirements


I can’t really find anything other than normal bike stuff. The big one there is you need a front and rear light if you’re going to be riding after dark. For this, I’m torn between wanting something shamelessly retro, like this, and something actually... good.

Looks like there is a pretty good crop of USB chargeable lights, so I think I’ll go that route and make sure there is a spot to put a big USB battery, that way we’re never caught short.



So... in a lot of ways this seems like a lot of fun.

This also seems like a massive waste of time and money.

All of this makes it a pretty ideal project for me.

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