Bsa B40 vs Kawasaki ZXR400

The Bsa B40 passes its MOT first time more often than the Kawasaki ZXR400: 90.6% vs 73.1%, a 17.5-point lead.

MOT reliability, side by side

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

Metric	Bsa B40	Kawasaki ZXR400
First-time pass rate	90.6%	73.1%
Outright fail rate	3.5%	18.9%
Vs comparable bikes (age & mileage adjusted)	+7.1 pts	-9.9 pts
Engine size	350cc	398cc
Rank among all models	#776 of 5428	#4490 of 5428
Median miles at test	8,069	23,651
MOT tests analysed	3,360	14,200
Most common failure	steering and suspension	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 B40	Kawasaki ZXR400
Lights & signalling	1.4%	9.1%
Steering & suspension	1.8%	7.9%
Brakes	0.7%	7.9%
Tyres & wheels	0.9%	4.0%
Fuel & exhaust	0.2%	2.4%
Structure & body	0.3%	2.2%
Drive system	0.3%	1.9%

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 B40	Kawasaki ZXR400
2011	88.9%	71.2%
2012	92.9%	69.5%
2013	88.8%	68.6%
2014	91.2%	70.6%
2015	89.4%	75.5%
2016	91.7%	75.6%
2017	89.6%	74.7%
2018	95.2%	75.9%

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 B40	Kawasaki ZXR400
0k-10k miles	91.2%	87.1%
10k-20k miles	88.5%	77.4%
20k-30k miles	90.4%	69.9%
30k-40k miles	92.0%	67.8%
40k-50k miles	90.0%	64.7%
50k-60k miles	90.2%	64.9%

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

Bsa B40 vs Kawasaki ZXR400 FAQ

answers computed from the data above · terms in the glossary

Which is more reliable, the Bsa B40 or the Kawasaki ZXR400?

The Bsa B40 passes its MOT first time more often than the Kawasaki ZXR400: 90.6% vs 73.1%, a 17.5-point lead. Adjusted for age, mileage and test class, the Bsa B40 still comes out ahead: +7.1 points vs comparable bikes for the Bsa B40, -9.9 for the Kawasaki ZXR400. An MOT checks roadworthiness items, not engine or gearbox internals.

What does the Bsa B40 fail its MOT on most?

Steering & suspension: 1.8% of Bsa B40 MOT tests failed on it, then lights & signalling (1.4%).

What does the Kawasaki ZXR400 fail its MOT on most?

Lights & signalling: 9.1% of Kawasaki ZXR400 MOT tests failed on it, then steering & suspension (7.9%).

Which holds up better at high mileage, the Bsa B40 or the Kawasaki ZXR400?

At 50k-60k miles the Bsa B40 passes first time more often: 90.2% for the Bsa B40 vs 64.9% for the Kawasaki ZXR400.

BSA B40 90.6% pass · 3,360 tests KAWASAKI ZXR400 73.1% pass · 14.2k tests

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