Ajs 18 vs Yamaha FZS600

The Ajs 18 passes its MOT first time more often than the Yamaha FZS600: 94.9% vs 82.6%, a 12.3-point lead.

MOT reliability, side by side

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

Metric	Ajs 18	Yamaha FZS600
First-time pass rate	94.9%	82.6%
Outright fail rate	1.9%	10.6%
Engine size	500cc	599cc
Rank among all models	#82 of 5428	#3052 of 5428
Median miles at test	15,812	21,612
MOT tests analysed	315	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 18	Yamaha FZS600
2006	100.0%	86.0%
2007	94.9%	84.1%
2008	94.4%	83.4%
2009	100.0%	81.2%
2010	94.1%	82.0%
2011	92.1%	81.1%
2012	93.5%	80.2%

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 18	Yamaha FZS600
0k-10k miles	92.7%	89.6%
10k-20k miles	97.8%	85.5%
30k-40k miles	95.2%	78.7%
50k-60k miles	100.0%	74.7%

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

AJS 18 94.9% pass · 315 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.