Data as of: DVSA MOT results to 2025
Ajs Firefox vs Piaggio NRG
The Ajs Firefox passes its MOT first time more often than the Piaggio NRG: 69.4% vs 65.5%, a 3.9-point lead.
MOT reliability, side by side
| Metric | Ajs Firefox | Piaggio NRG |
|---|---|---|
| First-time pass rate | 69.4% | 65.5% |
| Outright fail rate | 21.9% | 27.4% |
| Vs comparable bikes (age & mileage adjusted) | -5.2 pts | -6.0 pts |
| Engine size | 49cc | 49cc |
| Rank among all models | #4778 of 5428 | #4992 of 5428 |
| Median miles at test | 6,168 | 9,874 |
| MOT tests analysed | 1,537 | 40,458 |
| Most common failure | lamps and reflectors | lighting and signalling |
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
| Component | Ajs Firefox | Piaggio NRG |
|---|---|---|
| Lights & signalling | 13.4% | 15.0% |
| Steering & suspension | 9.8% | 15.5% |
| Brakes | 7.3% | 10.2% |
| Tyres & wheels | 2.9% | 4.7% |
| Structure & body | 4.0% | 2.5% |
| Fuel & exhaust | 0.1% | 3.8% |
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
| Test year | Ajs Firefox | Piaggio NRG |
|---|---|---|
| 2018 | 61.8% | 69.2% |
| 2019 | 70.1% | 68.0% |
| 2020 | 77.0% | 71.8% |
| 2021 | 64.4% | 72.9% |
| 2022 | 69.2% | 74.8% |
| 2023 | 67.9% | 77.5% |
| 2024 | 67.0% | 81.9% |
| 2025 | 73.3% | 77.1% |
Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.
Pass rate by mileage
| Mileage | Ajs Firefox | Piaggio NRG |
|---|---|---|
| 0k-10k miles | 71.1% | 71.3% |
| 10k-20k miles | 62.5% | 60.6% |
| 20k-30k miles | 50.0% | 55.7% |
Bands with fewer than 30 tests for either bike are left out.
Ajs Firefox vs Piaggio NRG FAQ
Which is more reliable, the Ajs Firefox or the Piaggio NRG?
The Ajs Firefox passes its MOT first time more often than the Piaggio NRG: 69.4% vs 65.5%, a 3.9-point lead. Adjusted for age, mileage and test class the two are level (-5.2 vs -6.0 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 Firefox fail its MOT on most?
Lights & signalling: 13.4% of Ajs Firefox MOT tests failed on it, then steering & suspension (9.8%).
What does the Piaggio NRG fail its MOT on most?
Steering & suspension: 15.5% of Piaggio NRG MOT tests failed on it, then lights & signalling (15.0%).
Which holds up better at high mileage, the Ajs Firefox or the Piaggio NRG?
At 20k-30k miles the Piaggio NRG passes first time more often: 50.0% for the Ajs Firefox vs 55.7% for the Piaggio NRG.
See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.