The pass rate is the MOT first-time pass: a roadworthiness check of the items an MOT covers (brakes, lights, tyres, steering, structure, emissions), not a full mechanical inspection of engine or gearbox internals. It is a reliability signal, not a complete measure of mechanical reliability. What this measures.
“vs expected” adjusts for age, mileage and test class, so a cherished classic and a hard-used commuter are compared fairly. How this works.
Pass rate by mileage
A low-mileage 850 passes first time 94.5% of the time; by 50k that's 96.7%.
First-time pass rate by odometer reading at test, 10,000-mile bands for this model. Mileage is the strongest reliability signal. See the full curve.
What fails on a 850
| Component group | Share of defects | Defects | % of defects |
|---|---|---|---|
| lighting and signalling |
|
3 | 60 |
| brakes |
|
1 | 20 |
| drive system |
|
1 | 20 |
Defects recorded against failed normal tests, 2005–2025, grouped by DVSA inspection section. One test can record multiple defects.
How rivals compare
On first-time pass rate the 850 beats 4 of its 4 closest rivals (KAWASAKI ZX-6R, SUZUKI GSF600, YAMAHA FZS600).
Rivals share this bike's type and sit within ±30% of its engine capacity, ≥ 5,000 tests. Card colour = better/worse first-time pass rate than the 850.
Compare with any bike
More NORTON models
Pass rate by registration year
Best year to buy used: 1974 (87.3% pass). Weakest: 1974 (87.3%).
First-time pass rate by the year each bike was first registered (cohorts with ≥ 50 tests). Older cohorts are survivors: the worst examples have already left the road, which tends to lift the earliest years.
Embed this bike
Free to embed on your site, blog or forum — a live Norton 850 reliability card that stays up to date and links back here. More on the free API page.