MC 75-05
Technical Support Report for Regulatory Action
Motorcycle Maintenance and Test Intervals
September, 1975
Notice
Technical support reports for regulatory action do not necessarily
represent the final EPA decision on regulatory issues. They are intended
to present a technical analysis of an issue and conclusions and/or
recommendations resulting from the assumptions and constraints of that
analysis. Agency policy constraints or data received subsequent to the
date of release of this report may alter the conclusions reached.
Readers are cautioned to seek the latest analysis from EPA before using
the information contained herein.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air and Waste Management
U.S. Environmental Protection Agency
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ABSTRACT
Maintenance and repair data from the Gallup Motorcycle Survey are
analyzed and test intervals for the emission and durability data vehicles
are determined. Scheduled maintenance intervals and the type of main-
tenance allowable for the durability vehicle are recommended. Major
engine repairs are also analyzed.
Prepared By
Approved - Project Manager
Motorcycles
/
r-J^&fc^^—
Approved - Branch Chief, SDSB
- Division Director
Distribution:
D. Alexander
E. Brune
T. Cackette
J. DeKany
C. Gray
D. Hardin
i. riuls
R. Jenkins
G. Kittredse
R. Stahr.an
E. Stork
G. Thompson
M. Williams
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INTRODUCTION
This report presents information on routine and major maintenance
of street legal motorcycles.
The Gallup Motorcycle Survey provided information on the frequency
of maintenance performed on motorcycles. The questionaire asked how
often the spark plugs were changed, the engine tuned up, the valves
adjusted or cylinder head decarbonized, and the carburetor cleaned or
disassembled. Answers in terms of miles or time (i.e. every 2 months,
etc.) were obtained.
The questionaire also asked how many miles were on the motorcycle
when various major repairs were first performed. Major repairs included
pistons and rings, valves, bearings, and carburetor replacement or
rebuilding.
Based on the average maintenance intervals and the useful life,
test intervals for the data and durability test vehicles were determined.
The major repair items were examined to determine if any major repairs
were likely to be necessary within the durability demonstration distance.
The analyses performed are based on street and dual purpose motor-
cycles with working odometers.
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SUMMARY A'.'?D CONCLUSIONS
o The scheduled maintenance intervals are 3000 km (< 170 cc) and 4000
kn (•_ 170 cc) , and are based on the average interval between tune
ups.
o Cylinder head decarbonization should not be allowed as scheduled
maintenance.
o Test points for the durability data vehicles are every 1500 km
(< 170 cc) and 5000 km (>_ 170 cc). A minimum of 12 emission tests
will be required for each displacement category.
o Within the useful life distance, there is a significant chance
major engine repair will be required. It is expected that engine
reliability may be a problem for the durability vehicle.
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.DISCUSSION
R ou t i n f M." 1 n t. ^ i n r. ?. rs
The GaliuD Survey induced ioar questions concerning the frequency
at which routine maintenance x/as performed. Each motorcycle owner was
asked how often tha following was cone to his or her motorcycle:
a. Change or clean plugs
b. Engine tune up
c. Decarbonizing the cylinder head or adjusting the valves
d. Disassemble and clean the carburetor
The owner could give several types of answers by responding with a time
(i.e. once a year), a distance (i.e. every 2000 miles), or a negative
answer such as "never", "haven't done yet", "don't know", etc.
For question c, it was assumed that only the 2-strokes required
decarbonization and only the 4-strokes required valve adjustments.
Table I presents the average distance and median time at which
routine maintenance was performed. The statistics are based only on
motorcycles for which, maintenance was performed, that is, the "don't
knows", "not yet" answers were not included.
Table I
Frequency of Routine Maintenance
(Based on thos..-. Performing Maintenance)
Average Distance, km Median Time, mo.
Type of Maintenance < 170 - 170 < 170 - 170
a. Plugs 1771 3359 6 4-5
b. Tune up . 2771 4009 12 12
c.l Decarbonise head
V-T -•_•_:' . . •+ / . — J^j'J .1 _ /--.
d. Cloa-.i ca. .iiroior 40'ib 7010 12 12
Also of interest is the percent of the population which actually
performed the routine maintenance. Table IT presents these data for
those motorcycles with at least as much accumulated distance as the
average distance at which maintenance was performed (from Table I).
Thus motorcycles with low accumulated distance, which may not have
needed routine maintenance yet, are excluded.
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Table II
Percent of Population Performing Maintenance
(Based on Motorcycles with Accumulated Distance >_ that shown in Table I)
Percent
Type of Maintenance • < 170 cc — 170 cc
a. Plugs 77 85
b. Tune up 65 78
c.l Decarbonize head (2-stroke) 41 44
c.2 Adjust valves (4-stroke) 49 58
d. Clean carburetor 51 49
Table II shows that the majority of the population has performed
plug changes and tune ups, about one half has performed carburetor
maintenance and adjusted valves, and less than one half has performed
cylinder head decarbonization. Although a tune up normally consists of
plug, ignition, and valve maintenance, the data indicate plug changing
or cleaning occurs more frequently and valve adjustments less frequently
than the tune up.
Based on these data, the average tune up interval is chosen as the
interval for allowable scheduled maintenance for durability vehicles.
The allowable scheduled maintenance intervals are,
< 170 cc 3000 km
>_ 170 cc 4000 km
and include ignition and spark plug maintenance, and valve and car-
buretor
... .y..- ' '• . :•. . •••:.'.-...••••.••:.-...• --TV • •-•:•:• •. . /-j,
cer.in-if' is :-c~. 'd ^.nr^J, 1: is expected chat: plug Ji:e t.-ili ••.icrease
as the unburnec HC aad oil emissions are reduced for controlled mctor-
cvcles. Also, an ov^rt ir'iication of spt'rk oluc r.isf i -ir-~ r:ir f.j?u'l t in
Including valve adjustments as part of the tune up (at a shorter
frequency than the data indicate) is based on similarity to the LDV
procedure and simplification of the durability test cycle.
Although carburetor disassembly and cleaning is performed by one
half the population at a distance less than the durability distance, it
is recommended that carburetor disassembly and cleaning not be allowed.
(Idle speed and mixture adjustments may be performed at the scheduled
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raaintenance points.) Due to the accelerated rate of mileage accumu-
lation, it is less likely that carburetors will need cleaning and
disassembly.
. To allow cylinder head decarbonization of 2-stroke engines as
scheduled maintenance means access to the combustion chamber must be
allowed, which is currently forbidden in the LDV procedures. The Gallup
data, however, indicate that this maintenance is performed by a signifi-
cant portion of the population. The pros and cons of allowing cylinder
head decarbonization are presented below:
Pro: - Gallup data indicate over 40 percent of 2-stroke motorcycle
owners perform decarbonization.
- Decarbonization is recommended in the owners manual of most
2-stroke motorcycles.
- Decarbonization of 2-strokes requires only the removal of the
cylinder head; other engine components are not disturbed.
Con: - Decarbonization requires access to the combustion chamber.
Decarbonization affects emissions. (The presence of carbon
deposits may increase HC and NOx emissions.)
Less than one half of the population of 2-stroke owners
performs decarbonization.
- Controlled motorcycles are less likely to need decarbonization.
The arguments against allowing cylinder head decarbonization outweigh
those in favor of it, and therefore it is recommended that cylinder head
decarbonization not be allowed as scheduled maintenance. Because this
decision is partially based on the survey question, which may have been
confusing (a large number of "don't know" replies occurred), the -aiestion
••" !••.>-...•:• ::r "-:.: i :-:::' •.} .' '•••-- -;-.---.-; •_. - -^-j ; •• *. :4.tior.r 1. •;*• .•• .- . •--.--
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Test Inervals -
The recommended test points for the emission data vehicle are:
< 170 cc 0, 2500 km
>_ 170 cc 0, 3500 km
The final test point was chosen to be at as large a distance as possible
to allow emission stabilization xdiile not exceeding the scheduled
maintenance distance. This reasoning was used because no information on
emission stabilization of motorcycles was available.
Test Intervals - Durability Data Vehicle
The durability data vehicle test points were chosen to minimize the
number of emission tests while still providing enough data points to
determine the deterioration factor. The test points are shown in Table
Ill-
Table III
Durability Data Vehicle Test Points, km
< 17Q cc - 170 cc
.0 0
1500 5000
3000 10,000
4500 15,000
6000 20,000
7500 25,000
9000 30,000
10,500
12,000
V- r.'\c.i::. "-, '.'•.'"ic^ --.c J;?v»"^ cr^rs Then ch^- s jl,-, ••i!:.Ifiu ^.lir:'-.•:;.->::;• ^ points
c^.n^i.'^? vvic'i dui"ij llitv tes-: poincs. S":nca en. erJ.ss'ior; t^-^t'i^ required
before and ai7ter "maintenance, the minimum number of emission tests
required will be: .
<• .i. u ^c :...- tiv.-.>i:.s •
_> 170 cc . 12 tests . .
For motorcycles with displacements greater than or equal to 170 cc, the
number of tests could be as many as 20 if the manufacturer chose to
perform scheduled maintenance at the minimum allowed interval of 4000
km.
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No scheduled r:-;ii:itcr!.a.r.cc- .ihall be performed after the following
accumulated distances:
< 170 cc 10,500 kn:
>_ 170 cc 28,000 km '
The tolerance on the test points is 250 km.
The Gallup Survey asked motorcycle owners what distance their
motorcycle had accumulated when piston and ring repairs were done the
first time. The question was repeated for bearing and valve repair.
The owner was also asked how many miles were on the motorcycle when the
carburetor was rebuilt or replaced.
The data were analyzed for original owner motorcycles only, because
for those motorcycles purchased used, the first time a repair is required
for the current owner may not be the first time the repair was performed
on the motorcycle. Table IV shows the percent of original owner motor-
cycles which required repairs and.. have accumulated distances greater
than or equal to the useful life.
Table, IV
Incidence of Major Repair
(Original Owner Motorcycles with Accumulated Distance >_ Useful Life)
Percent
]^^J^_]I:r22jLr < -70 cc — 170 cc
Pistons & Rings „ 21 23
Va.'.\\> : <.'2-i:trc::.?r 12 4*
• •- irt • 90
5 22
*Small sample size (27).
1 12,000 km for < 170 cc, 30,000 km for _> 170 cc.
2
Valve repair for 2-stroke engines is assumed to be repair to reed
or rotary valves.
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Ihci dii-~:i :-,-•..••'; c.ist for each major repair it era, less than one
quarter of thes.. oictorcycles exceeding the useful life distance has
required that specific repair. Table V presents the percentage of
motorcycles needing nc major repair of any type during their useful
life.
Table V
Motorcycles Requiring No Major Repair
(Original^Owner Motorcycles with Accumulated Distance 2l Useful Life)
Percent
< 170 cc 61
> 170 cc 51
The data in Table V show that slightly more than one half of those
motorcycles with accumulated distance greater than or equal to the
useful life have required no major repairs. The other one half have
required ar. -s^. c one of the major repairs.
Finally, the average accumulated distance .at which a major repair
was ::i .;t required is shown in Table VI. These data are based on all
oL'Li:ir-.a •. owner motorcycles without regard to the accumulated distance.
Table VI
Distance at which Major Repair was Required
(Original Owner Motorcycles)
I/O cc — 170 cc
Pistons and Rings? 4343 10,948
- - ,_ - ,; . ' -. ^ ... ,, G
>. a 1 v ~.~ 1.1 -3 •_ r ;:• !c c.! 479 7 19,612
Bearings 4618 13,400
Carburetor 3940 12,500
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.."rora tliii da.:..! sre^ert'.;.:! in TaKLes IV - VI, it can be deduced that
there is a good chance that a major internal engine repair will be
required by the time a motorcycle accumulates the useful life distance.
This assumes that the. distance accumulation occurs over the normal
lifetime of the motorcycle, whiirli is 5,5 years for small motorcycles and
7.3 years for largo motorcycles. With the accelerated distance accumu-
lation and rigorous maintenance of the durability vehicles, it is
expected that the probability of a major repair being needed will be
reduced. It remains, however, that reliability may be a major problem
for the durability vehicle.
Limitations of the Major Repair Data
The use of survey data to analyze major repairs, which may not have
occurred recently and require estimates of xjhat mileage the repair
occurred at, limits the confidence of the results. Because only a small
percent of the sample population is high mileage motorcycles, and due to
the limitation of considering only original owners, the sample size used
was small. There is also the limitation that motorcycles which have
accumulated the useful life distance (which these results are based on)
tend to be motorcycles which are 5 to 10 years old. It is possible that
the reliability of a current model year motorcycle may be much different.
Tha analysis of major repairs will be repeated if more useful
information such as fleet or service data become available; possibly
such data will appear in the concerts to the N?P.M.
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Distribution List
Motorcycle Technical Support Reports for Regulatory Action
D. Alexander
E. Brune
T. Cackette
J.P. DeKany
C.L. Gray
D. Hard in
K. Hellman
W. Houtman
T. Huls
R. Jenkins
E. Rosenberg
R. Stahman
E.O. Stork
G. Thompson
M. Williams
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