Bsa M21 Reliability, MOT Pass Rate & Common Faults
Free Bsa M21 car check
Is the Bsa M21 reliable? We analysed 963 real MOT tests across 232 vehicles to find out.
Got a specific Bsa M21? Enter the reg for a free check:
The Bsa M21 is above average for reliability based on real UK MOT data. Common problems include wheel bearings have excessive free play, position lamp does not illuminate immediately when it is switched on and headlamp at least one does not illuminate on dipped beam. Here's everything you need to know before buying a used Bsa M21.
Bsa M21 Number Plates
Number plates registered to a Bsa M21. Click on any registration for full vehicle details — including MOT history, mileage records, previous owners and damage history.
Bsa M21 MOT Pass Rate by Year
How likely is a Bsa M21 to pass its MOT? Here's the pass rate for each registration year, newest first.
Bsa M21 Problems — What Goes Wrong?
The most common reasons a Bsa M21 fails its MOT, ranked by how often they occur. Check for these problems before you buy.
Bsa M21 Mileage — What's Normal?
How many miles does a typical Bsa M21 owner drive per year? Use this to check if a car you're looking at has suspiciously low or high mileage.
Bsa M21 MOT Data by Registration Year
Full breakdown of pass rate and mileage for each year. Use this to compare the Bsa M21 year you're looking at.
| Year | Tests | Pass Rate | Low Mi. | Typical Mi. | High Mi. |
|---|---|---|---|---|---|
| 1961 | 103 | 94.2% | 20,018 | 35,489 | 56,684 |
| 1960 | 57 | 94.7% | 1,237 | 5,352 | 18,236 |
| 1955 | 54 | 94.4% | 7,282 | 36,194 | 63,185 |
| 1954 | 68 | 88.2% | 7,306 | 14,950 | 57,073 |
How Long Does a Bsa M21 Last?
Based on 232 Bsa M21 vehicles on UK roads.
Bsa M21 Mileage Distribution
Total mileage recorded across all Bsa M21 MOT tests. If the car you're looking at is above the 75th percentile, it's done more miles than most.
Best Year to Buy a Used Bsa M21
Based on MOT pass rates across all registration years with sufficient test data.
94.7% MOT pass rate from 57 tests
88.2% MOT pass rate from 68 tests
The best year to buy a used Bsa M21 is 1960, which has the highest MOT pass rate at 94.7% across 57 tests. The 1954 model year has the lowest pass rate at 88.2% — if you're looking at one from that year, budget for potential repairs and get a thorough pre-purchase inspection.
How Does the Bsa M21 Compare?
MOT pass rates compared to similar models. Click any model for the full breakdown.
| Model | Pass Rate | Tests | Typical Mileage | Lifespan |
|---|---|---|---|---|
| Bsa M21 THIS CAR | 93.0% | 963 | 25,700 mi | 72 yrs |
| Bsa A10 | 92.2% | 10,105 | 12,338 mi | 74 yrs |
| Bsa Bantam | 89.9% | 7,723 | 13,212 mi | 77 yrs |
| Bsa C15 | 90.2% | 6,096 | 14,541 mi | 67 yrs |
| Kawasaki Kle 650 Flf | 91.9% | 566 | 7,293 mi | — yrs |
Compared to the Bsa A10 (92.2% pass rate) and the Bsa Bantam (89.9% pass rate), the Bsa M21 outperforms both on MOT reliability.
Found a Bsa M21 you like?
Run a full vehicle history check on the specific car. See finance, stolen, write-off, mileage and MOT data for that exact vehicle.
Check a specific Bsa M21Should you buy a used Bsa M21?
The Bsa M21 has an overall MOT pass rate of 93.0% across 963 real MOT tests — comfortably above the UK average, which puts it among the more reliable models on UK roads.
The most common problems on the Bsa M21 are wheel bearings have excessive free play (5 recorded failures), position lamp does not illuminate immediately when it is switched on (4), and headlamp at least one does not illuminate on dipped beam (3). These are the faults most likely to cause an MOT failure on this model, so check for them carefully on any test drive or pre-purchase inspection. Many are wear-and-tear items that can be budgeted for, but a car that's already failing on multiple fronts may signal neglected maintenance.
A typical Bsa M21 owner drives around 227 miles per year. If the car you're looking at is significantly above this, expect more wear on suspension, brakes and tyres. If it's well below, the vehicle may have been sitting unused — check for perished rubber, corroded discs and stale fluids.
In terms of longevity, most Bsa M21 models stay on UK roads for around 72 years — a strong showing that suggests solid build quality and readily available parts. If you're buying one that's already approaching that window, the data suggests it has plenty of life left provided it's been maintained.
Before committing to a purchase, we recommend running a full vehicle history check on the specific car. This will reveal any outstanding finance, stolen markers, write-off history and mileage discrepancies that the seller may not disclose — and that the MOT data alone can't tell you.