HARLEY-DAVIDSON FAT BOY
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 over time
The FAT BOY's first-time pass rate has fallen 9.6 points since 2006, 97.1% to 87.5%.
Pass rate by mileage
A low-mileage FAT BOY passes first time 89.7% of the time; by 50k that's 85.7%.
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 FAT BOY
| Component group | Share of defects | Defects | % of defects | vs all bikes |
|---|---|---|---|---|
| lighting and signalling |
|
124 | 28.8 | 0.4× |
| lamps and reflectors |
|
80 | 18.6 | 0.8× |
| brakes |
|
67 | 15.6 | 0.3× |
| reg plates and vin |
|
44 | 10.2 | 1.2× |
| tyres and wheels |
|
24 | 5.6 | 0.3× |
| steering and suspension |
|
21 | 4.9 | 0.1× |
| structure and attachments |
|
20 | 4.7 | 0.6× |
| Identification of the vehicle |
|
18 | 4.2 | 1.7× |
| fuel and exhaust |
|
18 | 4.2 | 0.5× |
| tyres |
|
14 | 3.3 | 0.4× |
Defects recorded against failed normal tests, 2005–2025, grouped by DVSA inspection section. One test can record multiple defects. "vs all bikes" is how often this model's tests record a defect in the group, as a multiple of the all-bike rate.
How rivals compare
On first-time pass rate the FAT BOY beats 2 of its 4 closest rivals (HARLEY-DAVIDSON FLSTF, HARLEY-DAVIDSON FLSTC, HARLEY-DAVIDSON XL1200C).
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 FAT BOY.
Compare with any bike
More HARLEY-DAVIDSON models
Pass rate by registration year
Best year to buy used: 2010 (93.1% pass). Weakest: 2008 (78.9%).
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.
HARLEY-DAVIDSON FAT BOY FAQ
Is the HARLEY-DAVIDSON FAT BOY reliable?
The HARLEY-DAVIDSON FAT BOY is more reliable than average for its class: 88.9% of its 4,331 MOT tests (2005–2025) passed first time, against a class average of 84.9%. That ranks it #1305 of 5428 models.
What does a FAT BOY fail its MOT on most?
lighting and signalling — 29% of all defects recorded against failed FAT BOY tests.
What is the best year of FAT BOY to buy used?
By first-time pass rate, 2010-registered examples do best (93.1%) and 2008 worst (78.9%). Condition and history still trump the year.
How many miles will a FAT BOY last?
The median FAT BOY shows 14,959 miles at test, and examples around 50k miles still pass 85.7% of the time — mileage alone rarely kills one.
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