MZ Mastiff vs Yamaha FZS600

The Yamaha FZS600 passes its MOT first time more often than the MZ Mastiff: 82.6% vs 81.3%, a 1.3-point lead.

MOT reliability, side by side

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

Metric	MZ Mastiff	Yamaha FZS600
First-time pass rate	81.3%	82.6%
Outright fail rate	11.1%	10.6%
Vs comparable bikes (age & mileage adjusted)	-4.4 pts	-0.8 pts
Engine size	660cc	599cc
Rank among all models	#3318 of 5428	#3052 of 5428
Median miles at test	12,562	21,612
MOT tests analysed	888	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.

"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	MZ Mastiff	Yamaha FZS600
Lights & signalling	6.0%	3.4%
Brakes	2.9%	4.5%
Tyres & wheels	2.5%	2.9%
Steering & suspension	2.3%	2.7%
Structure & body	1.2%	1.1%
Fuel & exhaust	1.0%	1.1%
Drive system	0.7%	0.9%

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	MZ Mastiff	Yamaha FZS600
2013	69.5%	81.3%
2014	73.5%	81.2%
2015	82.2%	81.1%
2016	76.2%	82.2%
2017	83.7%	82.0%
2019	90.0%	83.0%
2021	90.9%	82.8%
2022	100.0%	83.6%

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	MZ Mastiff	Yamaha FZS600
0k-10k miles	80.5%	89.6%
10k-20k miles	82.4%	85.5%
20k-30k miles	78.2%	81.4%
30k-40k miles	84.2%	78.7%

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

MZ Mastiff vs Yamaha FZS600 FAQ

answers computed from the data above · terms in the glossary

Which is more reliable, the MZ Mastiff or the Yamaha FZS600?

The Yamaha FZS600 passes its MOT first time more often than the MZ Mastiff: 82.6% vs 81.3%, a 1.3-point lead. Adjusted for age, mileage and test class, the Yamaha FZS600 still comes out ahead: -4.4 points vs comparable bikes for the MZ Mastiff, -0.8 for the Yamaha FZS600. An MOT checks roadworthiness items, not engine or gearbox internals.

What does the MZ Mastiff fail its MOT on most?

Lights & signalling: 6.0% of MZ Mastiff MOT tests failed on it, then brakes (2.9%).

What does the Yamaha FZS600 fail its MOT on most?

Brakes: 4.5% of Yamaha FZS600 MOT tests failed on it, then lights & signalling (3.4%).

Which holds up better at high mileage, the MZ Mastiff or the Yamaha FZS600?

At 30k-40k miles the MZ Mastiff passes first time more often: 84.2% for the MZ Mastiff vs 78.7% for the Yamaha FZS600.

MZ MASTIFF 81.3% pass · 888 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.