Ajs 31 vs Yamaha FZS600

The Ajs 31 passes its MOT first time more often than the Yamaha FZS600: 91.2% vs 82.6%, a 8.6-point lead.

MOT reliability, side by side

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

Metric	Ajs 31	Yamaha FZS600
First-time pass rate	91.2%	82.6%
Outright fail rate	3.8%	10.6%
Engine size	650cc	599cc
Rank among all models	#645 of 5428	#3052 of 5428
Median miles at test	13,775	21,612
MOT tests analysed	422	136,558
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.

Pass rate by test year

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

Test year	Ajs 31	Yamaha FZS600
2007	90.9%	84.1%
2008	97.2%	83.4%
2009	97.3%	81.2%
2010	89.5%	82.0%
2011	93.9%	81.1%
2012	91.4%	80.2%
2015	87.5%	81.1%
2016	90.3%	82.2%

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	Ajs 31	Yamaha FZS600
0k-10k miles	93.2%	89.6%
10k-20k miles	84.8%	85.5%
20k-30k miles	90.4%	81.4%
30k-40k miles	89.2%	78.7%
40k-50k miles	94.4%	76.8%
50k-60k miles	90.3%	74.7%

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

AJS 31 91.2% pass · 422 tests YAMAHA FZS600 82.6% pass · 137k tests

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