Ajs Model 20 vs Yamaha FZS600

The Ajs Model 20 passes its MOT first time more often than the Yamaha FZS600: 90.3% vs 82.6%, a 7.7-point lead.

MOT reliability, side by side

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

Metric	Ajs Model 20	Yamaha FZS600
First-time pass rate	90.3%	82.6%
Outright fail rate	3.2%	10.6%
Engine size	500cc	599cc
Rank among all models	#854 of 5428	#3052 of 5428
Median miles at test	16,829	21,612
MOT tests analysed	308	136,558
Most common failure	steering and suspension	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 Model 20	Yamaha FZS600
2006	100.0%	86.0%
2007	88.2%	84.1%
2009	86.1%	81.2%
2010	85.3%	82.0%
2011	88.2%	81.1%
2012	90.0%	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 Model 20	Yamaha FZS600
0k-10k miles	86.8%	89.6%
10k-20k miles	94.0%	85.5%
20k-30k miles	94.7%	81.4%
30k-40k miles	87.1%	78.7%

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

AJS MODEL 20 90.3% pass · 308 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.