BIKERELIABILITY Reg check
League table/ BSA/THUNDERBOLT
Model report · 2005–2025

BSA THUNDERBOLT

650cc Petrol Class 2
#619 of 5428 overall #30 of 62 BSAs #377 of 2788 other bikes
91.3%
first-time pass rate
2.8%
failed outright
14,610
median miles at test
1,097
MOT tests, 2005–2025
+4.8pp
vs expected · age & mileage

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

first-time pass rate by test year · 2006–2017

The THUNDERBOLT's first-time pass rate has risen 1.6 points since 2006, 89.3% to 90.9%.

82%90%98%2006: 89.3% pass (75 tests)2007: 84.6% pass (78 tests)2008: 92.2% pass (90 tests)2009: 86.7% pass (90 tests)2010: 92.0% pass (75 tests)2011: 93.5% pass (92 tests)2012: 88.6% pass (88 tests)2013: 95.5% pass (88 tests)2014: 90.1% pass (101 tests)2015: 94.8% pass (97 tests)2016: 94.5% pass (91 tests)2017: 90.9% pass (88 tests)20062017

Pass rate by mileage

how the THUNDERBOLT's first-time pass rate falls with the odometer · class average 84.9%

A low-mileage THUNDERBOLT passes first time 90.0% of the time; by 40k that's 96.8%.

89%93%98%0k: 90.0% pass (438 tests)10k: 92.6% pass (230 tests)20k: 91.2% pass (226 tests)30k: 91.9% pass (86 tests)40k: 96.8% pass (31 tests)0k20k40k

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 THUNDERBOLT

failure defects by component group · advisories excluded
Component group Share of defects Defects % of defects vs all bikes
steering and suspension
17 28.3 0.4×
brakes
13 21.7 0.2×
lighting and signalling
12 20 0.2×
body and structure
5 8.3 0.9×
tyres and wheels
4 6.7 0.2×
fuel and exhaust
3 5 0.4×
driving controls
2 3.3 0.8×
drive system
2 3.3 0.3×
Other
2 3.3 —

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

same type, similar capacity, high test volume

On first-time pass rate the THUNDERBOLT beats 4 of its 4 closest rivals (KAWASAKI ZX-6R, SUZUKI GSF600, YAMAHA FZS600).

KAWASAKI ZX-6R 78.1% pass · 174k tests Compare head-to-head →
SUZUKI GSF600 77.3% pass · 143k tests Compare head-to-head →
YAMAHA FZS600 82.6% pass · 137k tests Compare head-to-head →
HONDA VFR800 FI 86.7% pass · 89.4k tests Compare head-to-head →

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 THUNDERBOLT.

Compare with any bike

rival not listed above? pick any model to see it head-to-head with the Thunderbolt

More BSA models

other BSA bikes ranked by MOT pass rate
BSA A10 91.6% pass · 10.2k tests
BSA BANTAM 88.7% pass · 7,202 tests
BSA C15 89.2% pass · 5,895 tests
BSA A65 90.9% pass · 5,064 tests
BSA B31 92.0% pass · 3,429 tests
BSA B40 90.6% pass · 3,360 tests

See all BSA models →

Pass rate by registration year

how each model-year cohort fares · registration year from first use date

Best year to buy used: 1966 (97.0% pass). Weakest: 1972 (85.8%).

84%91%99%1966: 97.0% pass (66 tests)1967: 87.9% pass (116 tests)1968: 89.3% pass (84 tests)1969: 92.6% pass (148 tests)1970: 92.8% pass (153 tests)1971: 93.1% pass (260 tests)1972: 85.8% pass (127 tests)196619691972

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.

BSA THUNDERBOLT FAQ

answers computed from the data above · terms in the glossary

Is the BSA THUNDERBOLT reliable?

The BSA THUNDERBOLT is more reliable than average for its class: 91.3% of its 1,097 MOT tests (2005–2025) passed first time, against a class average of 84.9%. That ranks it #619 of 5428 models.

What does a THUNDERBOLT fail its MOT on most?

steering and suspension — 28% of all defects recorded against failed THUNDERBOLT tests.

What is the best year of THUNDERBOLT to buy used?

By first-time pass rate, 1966-registered examples do best (97.0%) and 1972 worst (85.8%). Condition and history still trump the year.

How many miles will a THUNDERBOLT last?

The median THUNDERBOLT shows 14,610 miles at test, and examples around 40k miles still pass 96.8% of the time — mileage alone rarely kills one.

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