Anyone with DIY motorized bike experience? Considering building one!
Hi Tildes!
I'm a college student considering adding a gas motor onto my existing bike. I'm in a pretty hilly city, so biking around for groceries is kinda annoying... plus I wanna just zoom around some trails in my free time.
Currently, I'm looking at one of the 49cc 4 stroke engine kits all over Amazon/Ebay, since I heard that 4 stroke motors are supposedly quieter and more reliable than 2 strokes. I don't care about speed... in fact, I don't want to be going over 30mph on a bike. 49cc also makes this thing street legal in my state.
I did consider doing an e-bike conversion as well, but those are much more expensive... a 4 stroke kit is ~$160, while any reputable e-bike battery alone is more than that. These things don't burn much gasoline either, getting 100-150 mpg! I'd have to ride thousands of miles before the fuel cost exceeds an e-bike battery.
So, any advice would be appreciated! Also, I'd be willing to spend ~300 on this if there is a compelling reason to get a better motor than the generic Ebay one. If you have motor suggestions, please link them!
Thanks,
purpuraRana
Also curious about this, as well as the effort required to install one. How difficult is it? Could someone with little mechanical knowledge do it? What other maintenance will be required?
I built one of these in high school! What kit are you considering? I’m curious how much they have changed, as I’d say there are some serious limitations. Not that these aren’t fun, just that there’s usually some upgrades/modifications to make them work as desired.
It’s late on Friday pm here and I’m headed to bed, but I’ll try to post some more details with my experience tomorrow. IIRC, there’s a forum i found useful, gasbike or something similar.
Addendum:
Some things i remember: my kit was a 2 stroke 80cc and it required some modifications to make it work with my bike frame. Both in the down tube mounting bracket and with the exhaust. If it wasn’t for that, it would have been a pretty easy install.
Short comings of the kit:
All the hardware is cheeze-grade. Bolts like to loosen and bend. Expect to need to replace most of them, check them often, and use loctite.
The way the rear sprocket sandwiches the spokes on the back wheel has a tendency to break spokes and take the wheel out of true, though this is probably bike-dependent.
There’s no gear box so you get one gear ratio, so if you want to climb hills you won’t be seeing any significant speeds with it.
I have no experience with the 4 stroke kits, but I’ll say that 2 stroke almost always makes more power for the same displacement and rpm, and there’s far fewer moving parts. And i found the 80cc 2 stroke underwhelming, so i wouldn’t expect much from the 50cc 4 cycle.
All that said, these are tons of fun to learn some mechanical skills with, but I’d hesitate To make one my primary transportation.
Thanks for the reply!
I'm looking at something like this: https://www.ebay.com/itm/183413224196?hash=item2ab447b304:g:-oYAAOSw5Sdi338B&amdata=enc%3AAQAIAAAA8GCssw3%2FvXipDoLtx3XxUiWtYY2KX88G4AGayXhnWnSUB%2BXzgAuGrVAFkgQu2FtXFvIN5fmZ0OC2bdAaM4SPy%2BGIxCJ9YjcEEh5Dvhz6OwEOsy6WEFZ16VrtPJdJlxfhevt7Ad3iw9ALGJ2faWICSsctOfEIzi6LzVKerYUgRVpbt321iFQxHFwCiT8CuHrUKgphGRtTj9Q3lXg76llXI79qJn8giH03V0pu2IuuQDEAi3DCOmI%2BLSdXsrcwk8yGMtoFrdzQZ%2BsYwmOPBcpHJdhaXbzhntRB9pIhUllMx9VPfxqshCXkN%2FeCF%2FgdnU6mVw%3D%3D%7Ctkp%3ABFBMrPSZ8qZi
(though it seems like all the 49cc kits with that red engine cover are essentially the same thing)
I'm aware that there's likely gonna be some tinkering involved with getting it to fit my bike, but I should have access to a lot of tools at my college's makerspace. I can buy some loctite and better bolts at a nearby Home Depot.
How loud would you say your build was? One reason I want 4 stroke over 2 stroke is that they are supposedly quieter, and I don't want to be too annoying riding around the city. (I'm definitely not gonna be riding it on campus, don't want security confiscating it lol)
I hate to break it to you, but the 4 stroke is still going to be loud and annoying. It's literally a weedwacker engine. Can you get an idea of the sound from YouTube videos? They just don't put much of a muffler on those kits usually.
Also if you're trying to do hills I'm not sure how much torque the 49cc engines have, it might not carry you up hills as much as you'd want.
For what it's worth I put together a 1000w ebike for around $400ish, and it definitely has more torque for hills than a 49cc engine. But that was 7 years ago so take the cost with a grain of salt.
From the ones I watched, they were relatively quieter, but yeah I guess it would still be pretty loud overall.
For hills, I'm not expecting it to be able to provide all the power by itself; more of a pedal assist kind of thing.
Was your ebike setup a front hub, rear hub, or center mount? I might reconsider doing an ebike conversion instead if I can find a cheap battery that won't explode while charging...
Mine is a 48v 1000w rear hub - if I did it again I'd definitely do front hub instead, it was a little annoying having to fiddle with the rear derailleur. And my 1000w is kind of overkill on flat ground, it can hit like 35-40mph which is just unnecessary. But I think hub motors come in all different varieties of top speed vs torque, I'd rather find a higher torque/lower top speed 500w motor.
It's been on my project list to convert mine to run off 40v Ryobi lawn equipment batteries, 50% because I already bought into that ecosystem. So far I've been running hobby/RC car lipos, which do have the potential to be more dangerous like you said but I haven't had a problem yet and dang are they cheap.
Ive bought a mini bike frame and installed my own motor from a pressure washer - it was actually a Honda knock off 179cc engine and that engine runs amazingly well. But I have a little experience with the kind of cheap offshore knockoff engine that youre looking at for the bike conversion. The main downside is that its very unlikely to find parts for them if anything goes wrong - and at $149 for the engine and driveline, something will go wrong. But if its for occasional use and you can still pedal if it breaks down, maybe that's not a major deal for you. A four stroke is definitely quieter than a 2 stroke, but again, at that price, I highly doubt there's much sound deadening quality in that muffler - it'll be 'buzzy' but liveable. It would be a fun project, Id still do it for the heck of it, even if it only lasted for a year.
Make sure the components on the bike are good. Going 30mph is too fast if you don't have good brakes.