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Comment by wikidani | Hacker News Reader

Interesting, but to be completely honest, I think a two stroke motorized bike is better and a lot more fun to build

I live next to a bike lane, and there's a few assholes with two-stroke motorized bikes who use that bikelane regularly. I absolutely hate it, they make so much noise.

I hope the police catch them and take their bikes away.

I mean, they shouldn't use the bike lane. I agree with you. But, here's the thing. If they are not modified they are very quiet, noise codes should be enforced, but asking for their property to be pretty much stolen isn't a bit much?

A motorized “bike” is loud, smelly, expensive, much worse for the environment, and bad for your respiratory system.

I'm sorry, but I'd rather use a two stroke kit than dealing with all the ethical concerns of (for instance) the lithium batteries on ebikes. Also, when using the stock muffler and a right oil mix they are absolutely not smelly or loud. An argument could be made for the respiratory system, but I don't see how would that be an issue when these are used outdoors

Two strokes (and any other small engined scoot) qualify as low speed motorcycles here in Ontario. They require license, registration, and insurance. As a result, there is no market for them.

Ebikes on the other hand are legally bicycles. As long as you have pedals and officially limit yourself to 500W/32km/h, there are no restrictions.

At these low speeds, even a "small" 1kWh battery can run for two hours. That's 60-70km of range. Good for most commutes inside the city. Any further and you can take it with you on public transit that supports bicycles.

Really hard to make a case for two strokes here, maybe you live somewhere more forgiving.

I do, here they require no registration at all and they are considerably cheaper than ebikes. Also, I stated earlier that I don't feel entirely comfortable with the implications of lithium mining so I do try to minimize that as much as I can.

I contemplated something like that 20+ years ago, but also saw that there was at least one option with a small 4 cylinder engine that was reportedly quieter and able to run on straight unleaded IIRC.

Edit: a quick search shows those still available in 38, 49 and 79 cc models depending on the power needed. 100-150 mpg

I used to have one of those! I built it using a cheap 49cc conversion kit.

Honestly I'm not sure it was purely better: I had to pedal a bit before engaging the clutch to not stall the motor. It also became hard to breathe when stopped because of the fumes from the engine idling.

Was kinda fun to ride around though, but they outlawed them here. Guess other bike path users don't like smelling burnt oil...

Hi! I have a small 49cc kit too and never had an issue with fumes? Perhaps your oil mix is wrong? The one on the manual is way worse than using 40:1, perhaps you could try it if you get a chance. About the clutch issue, it sounds like you need some to make some changes to the flower nut maybe? I can start my bike without pedalling if I kick the floor to get some momentum.

They keyword there is "get some momentum"...it may not take much but definitely not as good as an electric motor that gives you full torque from 0. I actually managed to get it going from a dead stop by easing in the clutch and giving it a bit of gas but it smelled like burnt clutch afterwards :)

Lol at the downvotes, but yeah, nothing beats that for energy density. Could even carry a 1L bottle of petrol with you or something.

They're loud as hell and illegal in some places, though.

I'm actually a little curious about how great the practical energy density would be in this case with a 2-stroke engine compared to a modern lithium ion battery and motor. 2 stroke engines are pretty famously inefficient, expelling quite a bit of unburned fuel.

That and I'd guess that the engine itself is pretty bulky compared to the electric motor, so the total bulk might even out compared to an electric setup for the same amount of energy, but I'd have to look at the actual numbers.

I'm wondering what's the smallest possible fossil fuel _generator_ you could make, you could effectively make an ebike "hybrid" and it could be way more efficient since you can just run the engine at optimum speed constantly. Off-the-shelf units are 1000W, but a 200W constant unit would be the best.

This guy made a study: https://www.youtube.com/watch?v=1yB49G756OI

Batteries are still worse. Power to weight of a two cycle is extensive. In ideal conditions a two cycle eninge is more fuel efficient than a four cycle, but you only get about 50 rpm range where this is the case, and you need to be near full throttle. (Read you can prove this in the lab, but not in real world use)

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