ISO 21755-3:2025

International
Standard
ISO 21755-3
First edition
Motorcycles — Measurement
2025-11
method for evaporative
emissions —
Part 3:
VT-SHED test procedure
Motocycles — Méthode de mesure pour les émissions par
évaporation —
Partie 3: Protocole d'essai VT-SHED
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Evaporative emissions . 2
4.1 Description of VT- SHED test .2
4.2 Test motorcycle and fuel .3
4.2.1 Test motorcycles .3
4.2.2 Test fuel .3
4.3 Test equipment .4
4.3.1 Chassis dynamometer .4
4.3.2 Evaporative emission measurement enclosure .4
4.3.3 Analytical systems .5
4.3.4 Temperature recording system .5
4.3.5 Pressure recording system .5
4.3.6 Fans .6
4.3.7 Gases.6
4.3.8 Additional equipment .6
4.4 Test procedure .6
4.4.1 Test preparation .6
4.4.2 Fuel drain and refill .7
4.4.3 Pre-soaking .7
4.4.4 Pre-conditioning drive .7
4.4.5 Fuel drain and refill .7
4.4.6 Start soaking .7
4.4.7 Carbon canister loading .7
4.4.8 Dynamometer test .8
4.4.9 Hot soak loss (HSL) test.8
4.4.10 Soak .9
4.4.11 Diurnal breathing loss (DBL) test .9
4.5 Calculation of results .10
5 Calibration of equipment for evaporative emission testing .12
5.1 Calibration frequency and methods . 12
5.2 Calibration of the enclosure . 12
5.2.1 Initial determination of internal volume of the enclosure . 12
5.2.2 Determination of chamber background emissions . 12
5.2.3 Calibration and hydrocarbon retention test of the chamber . 13
5.3 Analytical systems .14
5.3.1 General .14
5.3.2 Hydrocarbon analyser .14
5.3.3 Hydrocarbon analyser data recording system . 15
5.3.4 Checking of FID hydrocarbon analyser . 15
6 Presentation of results . 16
6.1 The evaporative emission .16
6.2 Test report .16
Annex A (normative) Presentation of results for evaporative emissions . 17
Bibliography .20

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 38,
Motorcycles and mopeds.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
Recently, exhaust emissions from tailpipes of motorcycles have been dramatically reduced. Accordingly,
evaporative emissions have begun to attract attention. Therefore, measurement methods for evaporative
emissions are specified as an International Standard for multi-application, for example, certification,
research, developments and so on.
For motorcycles, the measurement method based on the sealed housing for evaporative determination
(SHED) method was conventionally specified, but not for the variable temperature sealed housing for
evaporative determination (VT-SHED) method, which matches the actual usage environment and has a high
accuracy of the test system. This document specifies the basic measurement method by using the VT-SHED
test procedure for evaporative emissions from motorcycles.

v
International Standard ISO 21755-3:2025(en)
Motorcycles — Measurement method for evaporative
emissions —
Part 3:
VT-SHED test procedure
1 Scope
This document specifies a basic measurement method by using the variable temperature sealed housing
for evaporative determination (VT-SHED) test procedure for evaporative emissions from motorcycles. It is
applicable to motorcycles equipped with a spark ignition engine (four-stroke engine, two-stroke engine or
rotary piston engine).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edi
...