Ajs JS vs Yamaha YBR 125

The Ajs JS passes its MOT first time more often than the Yamaha YBR 125: 71.2% vs 71.0%, a 0.2-point lead.

MOT reliability, side by side

first-time pass rate, outright fail rate and tests analysed · 2005–2025

Metric	Ajs JS	Yamaha YBR 125
First-time pass rate	71.2%	71.0%
Outright fail rate	20.2%	17.1%
Vs comparable bikes (age & mileage adjusted)	-1.4 pts	-1.1 pts
Engine size	124cc	124cc
Rank among all models	#4640 of 5428	#4664 of 5428
Median miles at test	9,562	10,652
MOT tests analysed	674	124,897
Most common failure	lamps and reflectors	brakes

First-time outcomes on normal tests, 2005–2025. "Most common failure" is the component group with the most recorded defects on failed tests. Read pass rates against test counts: a smaller sample is noisier. Source: DVSA anonymised MOT results.

"Vs comparable bikes" is the first-time pass rate minus the rate expected for each bike's own mix of age, mileage and test class, in percentage points: positive means better than comparable bikes. How this works.

What fails, side by side

share of each bike's MOT tests that failed on the component · lower is better

Component	Ajs JS	Yamaha YBR 125
Lights & signalling	10.5%	8.5%
Steering & suspension	7.3%	6.5%
Brakes	7.6%	5.9%
Structure & body	6.4%	3.8%
Tyres & wheels	4.7%	4.4%
Drive system	1.0%	2.9%
Fuel & exhaust	0%	0.6%

A test that fails on two components counts once in each. Component links go to the bikes most likely to fail on it.

Pass rate by test year

first-time MOT pass rate in each calendar year both bikes were tested

Test year	Ajs JS	Yamaha YBR 125
2018	68.0%	72.0%
2019	73.3%	71.8%
2020	64.5%	73.4%
2021	79.1%	71.6%
2022	78.9%	71.3%
2023	60.6%	71.1%
2024	76.5%	70.9%
2025	79.5%	71.2%

Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.

Pass rate by mileage

first-time MOT pass rate by miles on the clock at test

Mileage	Ajs JS	Yamaha YBR 125
0k-10k miles	75.4%	76.8%
10k-20k miles	67.5%	67.4%
20k-30k miles	60.0%	63.8%

Bands with fewer than 30 tests for either bike are left out.

Ajs JS vs Yamaha YBR 125 FAQ

answers computed from the data above · terms in the glossary

Which is more reliable, the Ajs JS or the Yamaha YBR 125?

The Ajs JS passes its MOT first time more often than the Yamaha YBR 125: 71.2% vs 71.0%, a 0.2-point lead. Adjusted for age, mileage and test class the two are level (-1.4 vs -1.1 points against comparable bikes), so the raw gap is mostly down to how old and how used each fleet is. An MOT checks roadworthiness items, not engine or gearbox internals.

What does the Ajs JS fail its MOT on most?

Lights & signalling: 10.5% of Ajs JS MOT tests failed on it, then brakes (7.6%).

What does the Yamaha YBR 125 fail its MOT on most?

Lights & signalling: 8.5% of Yamaha YBR 125 MOT tests failed on it, then steering & suspension (6.5%).

Which holds up better at high mileage, the Ajs JS or the Yamaha YBR 125?

At 20k-30k miles the Yamaha YBR 125 passes first time more often: 60.0% for the Ajs JS vs 63.8% for the Yamaha YBR 125.

AJS JS 71.2% pass · 674 tests YAMAHA YBR 125 71.0% pass · 125k tests

See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.