AJS 18S

500cc Petrol Class 2

#330 of 5426 overall #6 of 45 AJSs #203 of 2787 other bikes

92.8%

first-time pass rate

3.0%

failed outright

14,829

median miles at test

598

MOT tests, 2005–2025

Pass rate over time

first-time pass rate by test year · 2006–2012

The 18S's first-time pass rate has fallen 2.3 points since 2006, 95.6% to 93.3%.

Pass rate by mileage

how the 18S's first-time pass rate falls with the odometer · class average 84.9%

A low-mileage 18S passes first time 93.2% of the time; by 50k that's 84.4%.

First-time pass rate by odometer reading at test, 10,000-mile bands for this model. Mileage is the strongest reliability signal. See the full curve.

What fails on a 18S

failure defects by component group · advisories excluded

Component group	Defects	% of defects	vs all bikes
lighting and signalling	21	50	0.5×
steering and suspension	10	23.8	0.4×
brakes	3	7.1	0.1×
drive system	2	4.8	0.2×
reg plates and vin	2	4.8	0.3×
driving controls	1	2.4	0.7×
body and structure	1	2.4	0.3×
Items Not Tested	1	2.4	1.8×
fuel and exhaust	1	2.4	0.2×

Defects recorded against failed normal tests, 2005–2025, grouped by DVSA inspection section. One test can record multiple defects. "vs all bikes" is how often this model's tests record a defect in the group, as a multiple of the all-bike rate.

How rivals compare

same type, similar capacity, high test volume

On first-time pass rate the 18S beats 4 of its 4 closest rivals (KAWASAKI ZX-6R, SUZUKI GSF600, YAMAHA FZS600).

KAWASAKI ZX-6R 78.1% pass · 174k tests SUZUKI GSF600 77.3% pass · 143k tests YAMAHA FZS600 82.6% pass · 137k tests SUZUKI SV650S 80.6% pass · 84.6k tests

Rivals share this bike's type and sit within ±30% of its engine capacity, ≥ 5,000 tests. Card colour = better/worse first-time pass rate than the 18S.

Pass rate by registration year

how each model-year cohort fares · registration year from first use date

Best year to buy used: 1953 (98.9% pass). Weakest: 1955 (92.3%).

First-time pass rate by the year each bike was first registered (cohorts with ≥ 50 tests). Older cohorts are survivors: the worst examples have already left the road, which tends to lift the earliest years.

AJS 18S FAQ

answers computed from the data above · terms in the glossary

Is the AJS 18S reliable?

The AJS 18S is more reliable than average for its class: 92.8% of its 598 MOT tests (2005–2025) passed first time, against a class average of 84.9%. That ranks it #330 of 5426 models.

What does a 18S fail its MOT on most?

lighting and signalling — 50% of all defects recorded against failed 18S tests.

What is the best year of 18S to buy used?

By first-time pass rate, 1953-registered examples do best (98.9%) and 1955 worst (92.3%). Condition and history still trump the year.

How many miles will a 18S last?

The median 18S shows 14,829 miles at test, and examples around 50k miles still pass 84.4% of the time — mileage alone rarely kills one.