Bsa B31 vs Suzuki DR-Z400S

The Bsa B31 passes its MOT first time more often than the Suzuki DR-Z400S: 92.0% vs 80.4%, a 11.6-point lead.

MOT reliability, side by side

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

Metric	Bsa B31	Suzuki DR-Z400S
First-time pass rate	92.0%	80.4%
Outright fail rate	3.1%	11.1%
Vs comparable bikes (age & mileage adjusted)	+12.2 pts	-6.5 pts
Engine size	350cc	398cc
Rank among all models	#470 of 5428	#3493 of 5428
Median miles at test	15,803	6,940
MOT tests analysed	3,429	26,773
Most common failure	lighting and signalling	lighting and signalling

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.

"Vs comparable bikes" is the first-time pass rate minus the rate expected for each bike's own mix of age, mileage and test class, in percentage points: positive means better than comparable bikes. How this works.

What fails, side by side

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

Component	Bsa B31	Suzuki DR-Z400S
Lights & signalling	1.3%	6.1%
Brakes	1.3%	3.5%
Steering & suspension	1.1%	3.2%
Tyres & wheels	0.6%	2.6%
Drive system	0.3%	0.8%
Fuel & exhaust	0.2%	0.6%
Structure & body	0.1%	0.7%

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 B31	Suzuki DR-Z400S
2009	92.4%	78.2%
2010	91.9%	78.9%
2011	89.8%	78.3%
2012	92.6%	79.8%
2013	83.1%	77.6%
2014	87.5%	78.5%
2015	100.0%	79.9%
2016	87.5%	78.4%

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 B31	Suzuki DR-Z400S
0k-10k miles	91.6%	81.7%
10k-20k miles	92.8%	78.4%
20k-30k miles	92.0%	79.2%
30k-40k miles	91.9%	76.4%
40k-50k miles	90.3%	75.2%
50k-60k miles	93.0%	82.9%

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

Bsa B31 vs Suzuki DR-Z400S FAQ

answers computed from the data above · terms in the glossary

Which is more reliable, the Bsa B31 or the Suzuki DR-Z400S?

The Bsa B31 passes its MOT first time more often than the Suzuki DR-Z400S: 92.0% vs 80.4%, a 11.6-point lead. Adjusted for age, mileage and test class, the Bsa B31 still comes out ahead: +12.2 points vs comparable bikes for the Bsa B31, -6.5 for the Suzuki DR-Z400S. An MOT checks roadworthiness items, not engine or gearbox internals.

What does the Bsa B31 fail its MOT on most?

Lights & signalling: 1.3% of Bsa B31 MOT tests failed on it, then brakes (1.3%).

What does the Suzuki DR-Z400S fail its MOT on most?

Lights & signalling: 6.1% of Suzuki DR-Z400S MOT tests failed on it, then brakes (3.5%).

Which holds up better at high mileage, the Bsa B31 or the Suzuki DR-Z400S?

At 50k-60k miles the Bsa B31 passes first time more often: 93.0% for the Bsa B31 vs 82.9% for the Suzuki DR-Z400S.

BSA B31 92.0% pass · 3,429 tests SUZUKI DR-Z400S 80.4% pass · 26.8k tests

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