Bsa M21 vs Suzuki GSF600

The Bsa M21 passes its MOT first time more often than the Suzuki GSF600: 92.6% vs 77.3%, a 15.3-point lead.

MOT reliability, side by side

first-time pass rate, outright fail rate and tests analysed · 2005–2025

Metric	Bsa M21	Suzuki GSF600
First-time pass rate	92.6%	77.3%
Outright fail rate	2.3%	14.2%
Engine size	600cc	599cc
Rank among all models	#367 of 5428	#4013 of 5428
Median miles at test	22,787	21,080
MOT tests analysed	996	143,023
Most common failure	lighting and signalling	brakes

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.

What fails, side by side

share of each bike's MOT tests that failed on the component · lower is better

Component	Bsa M21	Suzuki GSF600
Lights & signalling	1.2%	6.7%
Brakes	0.4%	6.1%
Steering & suspension	1.2%	3.6%
Tyres & wheels	0.5%	3.3%
Structure & body	0.1%	1.5%
Drive system	0%	1.4%
Fuel & exhaust	0.2%	1.2%

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

first-time MOT pass rate in each calendar year both bikes were tested

Test year	Bsa M21	Suzuki GSF600
2009	93.0%	75.8%
2010	95.9%	75.8%
2011	91.5%	76.1%
2012	86.0%	75.9%
2013	93.3%	74.7%
2014	100.0%	75.0%
2015	93.3%	75.5%
2017	87.1%	77.0%

Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.

Pass rate by mileage

first-time MOT pass rate by miles on the clock at test

Mileage	Bsa M21	Suzuki GSF600
0k-10k miles	92.4%	86.8%
10k-20k miles	93.4%	80.1%
20k-30k miles	88.3%	75.2%
30k-40k miles	94.7%	71.3%
40k-50k miles	91.0%	69.4%
50k-60k miles	94.2%	68.3%

Bands with fewer than 30 tests for either bike are left out.

Bsa M21 vs Suzuki GSF600 FAQ

answers computed from the data above · terms in the glossary

Which is more reliable, the Bsa M21 or the Suzuki GSF600?

The Bsa M21 passes its MOT first time more often than the Suzuki GSF600: 92.6% vs 77.3%, a 15.3-point lead. An MOT checks roadworthiness items, not engine or gearbox internals.

What does the Bsa M21 fail its MOT on most?

Lights & signalling: 1.2% of Bsa M21 MOT tests failed on it, then steering & suspension (1.2%).

What does the Suzuki GSF600 fail its MOT on most?

Lights & signalling: 6.7% of Suzuki GSF600 MOT tests failed on it, then brakes (6.1%).

Which holds up better at high mileage, the Bsa M21 or the Suzuki GSF600?

At 50k-60k miles the Bsa M21 passes first time more often: 94.2% for the Bsa M21 vs 68.3% for the Suzuki GSF600.

BSA M21 92.6% pass · 996 tests SUZUKI GSF600 77.3% pass · 143k tests

See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.