Small-wheel riders get squeezed out of the conversion kit market. Most kits are made for full-size rims, so if you ride a 20-inch folder or a compact commuter, your options shrink to a handful of listings, and those listings tend to come from brands nobody has heard of.
YIYIBYUS is one of those brands. Their 20-inch rear hub kit costs less than almost everything else we track, and it promises the full parts set: motor wheel, controller, display, throttle, pedal assist sensor.
The catch is the customer record. Two ratings, one written review from July 2023, and in it the buyer explains they ordered the wrong wheel size and improvised their way around it.
That's not a disaster of a record. But it means the listing itself has to do the convincing, so it's worth reading the way a skeptic would. The spec table carries a number that doesn't add up, the warranty runs 90 days, and the wiring warning tucked into the notes tells you something about the support you should expect.
The verdict, straight: the YIYIBYUS 20 inch 1000W rear hub kit prices in the cheapest fifth of the 191 kits we track and its spec table is unusually complete for the money, but the entire owner record is one size-mismatch story and a 90-day warranty, so you'd be buying a promising parts list rather than any evidence of staying power.
That can work if you measure your fork and rim first and test inside the warranty window. If you want owners behind a kit, the conversion kit comparison table shows what a little more money buys.
Why it costs this little, and what the record holds
Start with the honest part: on our comparison table this sits in the cheapest fifth of the 191 kits we track, and the price is the strongest fact in its favor.
For it you get a 48V 1000W gearless rear hub motor, a controller, an SW-810LED display, a thumb throttle, a 5 magnetic point assist sensor, and a power cut-off brake lever. Tires are not included, and the listing says so.
Then the record, which is where the confidence drains out. Two ratings, both five stars, and one written review, posted in July 2023.
One person has found that text helpful. The second rating carries no words at all. A 5.0 from two ratings is not a fan base, it's a start, and the one text isn't new enough to say anything about how the kit holds up over years.
So this is a listing you have to evaluate on its own claims, and the claims are worth taking one at a time. The parts list is complete, the wheel size is printed in three separate places, and the spec table gives numbers that most budget listings leave out, which cuts both ways: there's more to check, and more that can disagree.
The one text is a size story, and it is the useful part
The buyer's account, in their own words, runs like this: it's a good motor, it works fine, but it wasn't what they expected. They expected a 27-inch kit and received the 20-inch one. Their fix was improvisation, a small tire in front and a bigger tire in the back, and they close with a thanks.
Everything useful in that text is the mistake. The listing's own Note bullet warns "Please check the product size before purchasing," and this buyer is the person that warning was written for.
The title says 20 inch, the spec table's wheel size row says 20 inches, the rim size row says 20 inches, and tires don't come in the box. A 20-inch kit doesn't fit a 27-inch wheel, and this owner improvised with mismatched tires rather than boxing the kit back up. Order the wrong size and the fix is on you.
The praise in the text is thin. "It works fine" appears twice, and that's the whole durability signal: one person, one install, one early result, three years old now. Treat the review as evidence the motor runs and nothing more.
The lesson worth taking is the measurement habit, because the record shows exactly what skipping it costs.
Reading the spec table like a skeptic
The controller row reads 48V 130A, and that number deserves a second look. A 1000W motor at 48V draws about 21 amps continuous, so a controller passing 130 amps into it makes no sense as output. The likeliest readings are that 130 is a model number or a typo, and nothing on the page settles it.
Budget your battery around the motor's draw, about 21 amps with headroom, not around the row.
The speed claim is 50km/h, about 31 mph, printed twice. Nothing on the record measures it, and the listing gives no rpm figure to check it against, so it stays the seller's number.
What the table does give you is unusual completeness for this tier: rear fork open size of 135mm, brake compatibility with both V brake and disc, a 5 magnetic point assist sensor, and a display model you can actually look up.
One bullet is worth quoting to yourself before checkout. The wiring note says to connect the controller wires by matching colors, "Otherwise, the controller may be broken." That's an honest concession, and it tells you the install expects care that the support behind it may not.
The brand is YIYIBYUS and the manufacturer row reads LIEASTGY, the alias-brand split we keep finding in this tier.
The 90-day question
The warranty row says 90 days. Kits one price band up commonly carry a year, and some budget sellers commit to two, so 90 days covers the install and the first rides and little after. With a record this thin, that row is the only durability signal the listing offers, and it's a short one.
The combination to weigh is the wiring warning plus the window. If a color gets crossed and the controller dies during the install, 90 days should still cover it, which is the good news.
The bad news is that month-four failures, the kind that show up in hub motor records once owners have real miles on a kit, would land entirely on the buyer. Nothing in the record says this kit fails at month four. Nothing says it doesn't, either.
The best sellers rank row places the kit deep in a broad Sports & Outdoors category, which fits a low-volume listing that sells a few units a month. That's normal for this tier and not a mark against it. It just means the crowd won't catch problems for you, so the return window and the warranty window are the safety net, and one of them is short.
Fit, brakes and law, before checkout
The measurements come first. The rear fork open size is claimed at 135mm, which is the standard spacing for most steel and aluminum frames, but measure yours anyway, because this is the one number that sends a kit back. The rim is 20 inch, printed in the title, the wheel size row, and the rim size row, and the kit takes 20-inch tires you supply yourself.
The physics come second. Hub motor mass rides inside the wheel, where it counts as unsprung weight and gets less shielding from shock and debris than a frame-mounted motor, per Wikipedia's hub motor overview, and a gearless direct-drive hub makes its torque by being larger rather than geared.
On a 20-inch wheel the motor sits close to the ground and the steering is quick, so check that the 20.9 pounds of kit weight suits a small frame.
Then the law. A 1000W motor sits above the 750W continuous cap that US three-class definitions set for street-legal ebikes, so where you can ride it depends on your state's rules. And if the record still feels too thin, the conversion kit comparison table sorts every kit we track by price.
FAQ
Is a battery included?
No. You need a 48V pack rated for at least 21 amps continuous to feed a 1000W motor with headroom. Ignore the controller row's 130A figure when sizing the pack, since the motor's actual draw is what matters.
What bikes does it fit?
20-inch rear wheels with a 135mm rear fork spacing, and it supports both V brake and disc brake. Tires are not included. One buyer ordered while expecting a 27-inch kit, so measure the fork and the rim before checkout rather than assuming.
How fast does it go?
The listing claims 50km/h, about 31 mph, printed in two bullets. Nothing on the record measures it, and the listing prints no rpm figure to verify against, so treat it as the seller's number.
What is the warranty?
90 days per the spec table. That covers the install window and little after, which is short next to the one- and two-year rows common one price band up.
Why did the reviewer get the wrong size?
They ordered while expecting a 27-inch kit. The listing is 20 inch only, and the mistake cost them an improvised fix with mismatched tires. It's the exact scenario the listing's own "check the product size before purchasing" note exists to prevent.