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Exhaust Sound Emissions from Classic and Vintage Motorcycles

By Allan Johnson, B.S.A., M.Sc.

51 Market St., Georgetown, ON, L7G 3C4

Tel. 1(905) 877-1565

Email: afjohnson@sympatico.ca

Introduction

Proposals have been made by the Canadian motorcycle industry association (MMIC) that

a recently developed Society of Automotive Engineers (SAE) on-road motorcycle sound

emission test, known as SAE J2825, be adopted by Canadian municipalities and their

police forces in order to control motorcycle noise. Promotion of this roadside stop and

test program raised questions amongst Canadian Vintage Motorcycle Group (CVMG)

members as to whether their Vintage and Classic motorcycles would be able to pass such

a test, since most of their motorcycles were manufactured before there were any required

Canadian national numerical standards for allowable sound emission levels.

A preliminary sound testing program on 52 Vintage and Classic motorcycles was

conducted at the CVMG Annual Rally held at Paris, Ontario from June 18 – 20, 2010.

The following is a report of the testing undertaken, the results obtained and some

observations on the findings.

Materials and Methods

The test instruments were those of the type used by the Canadian Motorcycle Association

(CMA) and its member clubs for official testing of CMA and FIM sanctioned

competition events requiring testing to the SAE J1287 protocol – a sound measurement

testing protocol and standard for off-road motorcycles.

The Digital Sound Level Meter used was an Extech model 407740, an Extech model

407744 Sound Level Calibrator was used as a 94 dBA calibration standard and where

the motorcycle being tested did not have a tachometer, a Treysit sirometer placed on the

bike’s saddle or rear fender was used to adjust the bike’s engine to 2000 or 5000 rpm.

A small, marked wooden plate was used to gauge the correct 45 degree angle of

measurement from the end of each silencer tip. It was removed before testing was done to

eliminate any sound reflection from the plate, the 45 degree angle being then indicated by

an appropriately placed narrow stick of soft wood radiating from below each exhaust

outlet. A distance gauge to accurately place the sound meter 50 cm from the silencer tip

on the 45 degree axis and at a height above ground equal to the silencer tip distance from

the ground was constructed of soft wood so as to hold the sound meter in the correct

position and alignment for each exhaust tip. This gauge also allowed the calibration unit

to be rapidly deployed to check the sound meter calibration. The sound meter was used

with the foam diffuser ball in place, except when calibrating the meter. Before the sound

meter was placed in the testing position it was pointed away from the test bike to check

that the background noise level was sufficiently low for a valid bike test to be conducted.

The sound meter was steadied in place by hand while readings were being taken. If a

motorcycle had two separate exhausts on opposite sides of the motorcycle the sound

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levels at each silencer outlet were separately measured and recorded, then averaged for

statistical purposes. Where a silencer outlet was a circular pipe, the 50 cm distance was

measured from the center of the pipe orifice. If the silencer outlet was a slot as was usual

with the “fishtail” form of silencer exit port, then the 50 cm distance was measured from

the mid-point between the two lobes of the tail.

All tests were done on motorcycles placed on their center or rear stands or held in a

vertical position to ensure consistency. Side, prop or “jiffy” stands were not used. If the

bike was being held vertically and/or the operator was operating the throttle, they stood

on the side of the motorcycle away from the sound meter. The motorcycle was at least 10

feet away from any other motorcycle or other object. Only the person holding and

reading the sound meter was near the meter. The ground under all the test bikes was a

mowed, compacted grass field. Weather conditions on all three test days was in the 25 –

30 degrees C range and sunny.

Emphasis on selection of motorcycles tested was on motorcycles manufactured prior to

the silencer noise limit standards brought in by the Canadian federal government for 1983

model year and subsequent year manufactured and imported motorcycles. 48 of the tested

motorcycles were 1982 or earlier models whose exhausts systems were not subject to any

numerical sound limit regulation at the time of manufacture. Of the four remaining

motorcycles, one was a 1988 motorcycle with stock exhaust system and three were post-

1982 models with aftermarket or home-made exhaust systems.

Results

The individual results for each of the 52 motorcycles tested with details of the tested

vehicle, the exhaust system used and other details are presented in Appendix A. Twenty-

nine different makes of motorcycle were tested and these ranged in model year from 1913

to 2000.

All 52 of the motorcycles tested at idle speed were found to emit less than the 92 dBA

idle speed limit proposed by SAE test J2825. The quietest motorcycle at idle, a 1978

BMW 980cc opposed 4stroke twin, registered under 69 dBA.

2 elderly (1914 and 1928) twin cylinder motorcycles with stock exhaust systems were

found to emit greater sound levels than the 96 dBA SAE J2825 proposed limit at 2000

rpm. 2 further motorcycles (a 1942 twin and a 1984 4 cylinder), each with a non-standard

exhaust system, were found to exceed their respective 96 dBA and 100 dBA SAE J2825

proposed limit. The remaining 48 motorcycles (43 with stock exhaust systems and 5 with

“aftermarket” or non-stock exhaust systems) recorded less than the 96 dBA at 2000 rpm

or 100 dBA SAE J2825 proposed limits for their respective engine cylinder class.

The motorcycles tested were grouped by engine cylinder number, and in some cases

engine type and size in order to provide the summary statistics presented in Table 1.

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Table 1. Summarized results of Vintage and Classic motorcycle sound testing at the

CVMG Paris Rally, June 18-20, 2010. dBA values in Mean and range. (NA – not

applicable. < equals “less than”. Stock ex. = Stock, original type exhaust system)

Motorcycle Class # Idle dBA 2000 rpm dBA 5000 rpm dBA

------------------------------- ----------------------- ------------------- -------------------

1 cylinder, 4 stroke 500cc 9 83.1 (80.2 – 86.5) 93.7 (88.1 – 96.0) NA

(1913- 1979) Stock ex.

1 cylinder, 4 stroke <250 cc 3 78.4 (71.0 – 84.1) 90.5 (86.1- 94.7) NA

(1968-1971) Stock ex.

1 cylinder, 2 stroke <250 cc 6 80.6 (72.0 – 89.0) 92.6 (86.5 – 96.0) NA

(1922 – 1975) Stock ex.

2 cylinder, 4 stroke, Stock ex. 18 83.0 (68.7-92.7) 89.8 (79.4 – 98.0) NA

(1914 -1988) 250 –1,000 cc

2 cylinder, 4 stroke, Non-stock 5 86.7 (79.0 –91.9) 94.3 (90.2 – 106.0) NA

ex. (1940-2000) 650-1,700cc

2 cylinder, 2 stroke, Stock ex. 1 91.8 100.0 NA

(1928) 500 cc

3 cylinder, 4 stroke, Stock ex. 1 83.8 90.1 94.2

(1971) 750 cc

3 cylinder, 4 stroke, Non-stock 1 77.0 86.0 98.6

ex. (2000) 900 cc

4 cylinder, 4 stroke, Stock ex. 6 82.6 (76.1-89.3) NA 97.0 (95.8-100.0)

(1925 – 1977) 400 –1200cc (note 1)

4 cylinder,4 stroke, Non-stock 1 79.0 101.4

ex. (1984) 750 cc

Wankel rotary engine, Stock 1 84.0 86.4 97.0

ex. (1976)

(Note 1: four of the six motorcycles in this group were 1925 to 1947 models not designed

to be operated at levels as high as 5,000 rpm so their dBA readings above idle rpm were

taken as a “flash” reading at momentary wide open throttle.)

The Vintage and Classic motorcycles tested consisted of a variety of original and

unrestored, original and maintained, and restored to original specification vehicles. It is

therefore no surprise that the sound level values vary considerably from motorcycle to

motorcycle. It must also be realized that prior to the 1983 model year, motorcycles sold

new in Canada were not subject to any numerical sound standards criteria. There were no

such Federal regulations until that year and sound emissions from motor vehicles were

generally regulated by provincial highway traffic laws or local nuisance control by-laws.

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It was, therefore, the role of the motorcycle manufacturers prior to the era of government

regulation to fit what they considered adequate silencing equipment to their motorcycles.

To-day’s motorcycles use modern sound attenuation technology such as double-walled

pipes, sound-absorbent packing and computer-designed chamber and pipe dimensions.

The makers of early motorcycles were without such advantages. As well, most

motorcycle manufacture was carried on by relatively small factories without the research

and development resources to design and test sound control systems. It was not until the

1960’s, with the rise of large motorcycle manufacturers making hundreds of thousands of

motorcycles per year that research and development on motorcycle sound levels became

common.

That is not to say that the problem of excessive sound from motorcycle exhaust systems

was not recognized much earlier than the 1960’s and motorcycling literature from the late

1920’s onwards indicates that in Britain, then the world’s largest motorcycle

manufacturing country, quiet motorcycles were a design and manufacturing objective.

Much media attention and advertising was centered on motorcycle maker’s efforts to

produce motorcycles with low sound emissions.

It is therefore refreshing to find that in nearly all the cases of the antique and classic

motorcycles tested in this study that those with stock (standard) types of exhaust system

as originally fitted were able to control sound levels to at or below the criteria proposed

in the SAE J2825 test.

Both single and twin cylinder four stroke stock exhaust motorcycles produced average

idle values about 9 dBA below the J2825 allowed criterion. For the J2825 2000rpm 96

dBA criterion the 500 cc 4 stroke singles averaged just over 2 dBA below that criterion,

while the 4 stroke twin cylinder bikes, although generally larger in engine size, averaged

6 dBA below the allowed 96 dBA criterion.

The small two-stroke singles averaged 11 dBA below the 92 dBA idle allowed criterion

and just over 3 dBA below the 96 dBA at 2000 rpm allowed criterion.

Small 4 stroke singles, even though two of the three motorcycles tested were competition

types, averaged 13 dBA below the J2825 idle criterion and 5 dBA below the 2000 rpm

(96 dBA) criterion.

Twin cylinder motorcycles with non-stock exhaust systems averaged 5 dBA below the

idle criterion and 1 dBA below the 2000 rpm criterion of 96 dBA. The 5 motorcycles in

this group included the motorcycle which had the highest recorded 2000 rpm sound test

in this study at 106 dBA. This modified 1942 Indian Scout 800 cc side valve v-twin was

equipped with a 2 into 1 exhaust pipe and a “Brooklands Can” pattern of silencer

originally designed in 1907 to attenuate racing car and motorcycle exhaust sound from

the Brooklands race track at Weybridge, Surry, England. It appeared to be sized for a

smaller engine than the one it was fitted on and this may be the reason for its

ineffectiveness.

Another motorcycle, a 650 cc twin “Chopper” without any silencers at all was only 2

dBA below the idle criterion but was 5 dBA below the 2000 rpm criterion, an unusual

situation. This anomaly appears to result from the builder welding a “half washer” inside

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each exhaust pipe to act as a silencer. This resulted in such restriction to gas flow that the

engine could not properly run at higher revolutions – but it did limit the sound level

significantly.

Only two 3 cylinder motorcycles were tested, one 1971 motorcycle of 750 cc with a

stock exhaust system and it was 8 dBA below the idle criterion and over 5 dBA below the

5000 rpm test criterion. The 900 cc 3 cylinder motorcycle with a “factory off-road”

exhaust system was 15 dBA below the idle criterion and 1 dBA below the 5000 rpm test

criterion.

Of the six four cylinder motorcycles tested in this study four of them were designs which

originated 70 or more years ago. As such, they were not capable of reaching the 5000

rpm test level required by the SAE J2825. As a result, the “high rpm test” was done as a

“flash” full throttle reading of the highest dBA reading obtained. Since none of these four

motorcycles were equipped with their own tachometers and the sirometer must be preset

to a known rpm value in order to operate properly, accurate rpm measurement was not

attainable. Nevertheless, the idle dBA of the six motorcycles averaged 9 dBA below the

SAE J2825 idle criterion and the maximum throttle average value was 3 dBA below the

5000 rpm criterion. Since these elderly engines were intended to operate at much lower

revolutions than 5000 (generally in the 3500 rpm range or less) it would be more

appropriate for them to be tested at the 2000 rpm criterion level. Two of these

motorcycles had attached hard-bodied sidecars on the same side of the motorcycle as

their single exhaust pipes. It was noticed that some sound reflection from the sidecars

was affecting the dBA readings from the exhaust.

The single 1928 twin two-stroke tested met the 92 dBA idle criterion but exceeded the

2000 rpm criterion of 96 dBA by 4 dBA. The simple expansion box and narrow tailpipe

exhaust system traditional on this make and model are usually more effective and it may

be that the expansion box attenuation wire packing was missing.

The single Wankel-type rotary engined motorcycle was tested at all three criteria and

was well below the proposed allowable dBA levels.

Observations and Conclusions

1. The preliminary study reported here generally indicates that Vintage and Classic

motorcycles of 1, 2, 3 and 4 engine cylinders and Wankel rotary engines with stock

(standard pattern for year, make and model) exhaust systems in good (as designed and

manufactured originally) condition will test at lower decibel (dBA) levels than permitted

by the proposed SAE J2825 stationary on-road motorcycle sound test.

2. The report does indicate that some old design (1930s and earlier) four cylinder

motorcycles cannot reach the 5000 rpm test level for 4 cylinder motorcycles and should

either be allowed to test at the lower (2000 rpm) level, although they do meet the

100dBA criterion at momentary maximum revolutions, or be exempted from testing

altogether.

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3. On certain Vintage and Classic motorcycles which are equipped with sidecars on the

same side of the motorcycle as the exhaust system, there is some effect on sound readings

from reflection off the hard body of the sidecar.

4. With some motorcycles with hard saddle cases there may be significant measurable

reflection of sound towards the sound test meter from those cases, especially if the

motorcycle is not tested in an vertical position but tested when leaned over to one side on

the side, prop or jiffy stand and the measurement taken on the silencer on the side

opposite to the side stand. (Usually the right side of the motorcycle, the side stand being

normally on the motorcycle’s left side.)

5. Engine noise from valve gear and other exposed components on very early

motorcycles can be a significant sound contributor, although the exhaust sound itself

may be of limited volume, particularly at idle.

6. While the SAE J2825 proposed stationary on-road motorcycle sound test addresses the

issue of whether a single motorcycle may be “too noisy”, it does not address the real

problem of particular community disturbance from numbers of motorcycles, and other

vehicles, operating along public roads. The inverse square law of acoustics states that

Sound Pressure Level varies inversely as the square of the distance from the source. In

regard to a point source, such as a single motorcycle exhaust, where there are no

reflecting surfaces, background sounds or interference, a sound level drops 6 dB for

every doubling of the distance from the source.

However, in traffic sound studies along a linear corridor or road, the traffic sound of a

number of vehicles is considered a “line source” which produces cylindrical spreading of

the sound to the roadsides. This results in a sound level reduction of only 3 dB per

doubling of reception distance. This is half of the attenuation which would occur from a

point source such as a single motorcycle exhaust. A long parade of motorcycles on a

group ride – even if each individual motorcycle in the parade met the SAE J2825 test for

allowed sound emission – would result in a higher level of noise reaching the roadside

community.

7. Although a motorcycle may be able to pass the SAE J2825 test, it is well understood

by many motorcyclists that inappropriate use of large throttle openings in lower gears,

racing the engine in neutral, violent acceleration, ignition switching, and such tactics can

cause objectionable noise with almost any motorcycle. It would seem unlikely that a

program of roadside motorcycle sound testing would be conducted at such times and

places as to deter such sporadic antisocial behaviour. Thus, while SAE J2825 may

measure the motorcycle’s capability to be operated within certain sound level guidelines,

it cannot affect the motorcycle operator’s use and behaviour without significant and

expensive police enforcement effort.

8. It is well recognized in the motorcycling community that although Federal government

standards for sound level control in motorcycle exhaust systems have been in force since

1983, it is still possible to purchase new motorcycles from franchised dealers in this

country and have non-road legal, noisy, exhaust systems (some provided by the

motorcycle manufacturer) fitted to these motorcycles. Comments by CVMG members

who volunteered their motorcycles for this sound testing project invariably mentioned

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that in their experience, the real motorcycle noise problem is with purchasers of new

motorcycles who are enamoured of the “biker image” and feel that the installation of an

noise-producing “factory off-road racing” or “aftermarket performance” exhaust system

somehow “enhances their self-image.”

Figure 1. Sound Level meter, Calibration source and sirometer used in testing.

(See attached figure IMG_1504.jpg)

Figure 2: Alignment method and gauge for Sound Level measuring.

(See attached figure IMG_1500.jpg)

Sound Test Individual Results for “Exhaust Sound Emissions from Classic and

Vintage Motorcycles” Report.

Appendix 1 : Results of individual motorcycle sound emission testing at the CVMG

National Vintage Motorcycle Rally, Paris, Ontario, June 18-20, 2010

( m/c = rpm measured by the motorcycle tachometer, S = rpm measured by sirometer,

R = right silencer value, L = left silencer value, K = 1000 rpm)

Motorcycle dBA values obtained Comments

Year, Make model Idle 2K 5K other

Engine size/type

----------------------------- -------------------------------------- ---------------------------

1978 BMW R100/7 68.7R 79.9R (4K)92.8R Stock pattern old

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980 cc 4str opp.twin 68.7L 78.9L (4K)93.4L silencers, unrestored,

low compression, 68.6R (without Craven pannier bags) m/c

small carb version 68.5L ( “ “ “ “

1938 Brough Superior SS80 82.0 93.0 (silencer only) Stock pattern silencer

990 cc, v-twin, side valve 79.0 90.0 (silencer plus (carbjector type) and

stock “fishtail”) cast alloy fishtail. S.

92.5 at 50% power (2200 rpm)

1926 Nimbus “Stovepipe” 86.0 100 at max.rpm 4 into 1 short ex.

750 cc Ioe inline 4 cyl. (standard system)

no expansion box

or silencer body. S.

1922 Neracar 2 stroke 84.0 93.2 expansion box and

220 cc single TS ex.pipe outlet under

floor pan. S.

1947 Nimbus “Bumblebee” 84.2 95.1 (max rpm) 4 into 1 short stock

750 cc ohc inline 4 ex.pipe oval small

outlet close to right

hand metal Steib

sidecar.

Restored. S.

1975 Batavus moped 78.8 94.1 stock original ex.

2 stroke 1 cyl. 50 cc pipe. S.

1968 Norton Atlas 84.1R 91.4R Reproduction ex.

750 cc ohv 4 stroke 84.2L 92.1L to original pattern

twin Restored. m/c.

1955 Ariel VH 81.0 94.7 Reproduction ex.

500 cc ohv 1 cyl to original type.

Restored. S.

1976 Suzuki RE5 84.0R 86.1R 97.0R Stock original

Wankel-type rotary 84.0L 86.7L 97.0L exhaust. m/c.

1967 Triumph T20SM 84.1 94.7 Stock off-road

“Tiger Cub” 200 cc exhaust. S.

4 stroke single

1950 AJS 18S 80.2 88.1 Stock “Burgess”

500 cc ohv 1 cyl. style silencer. S.

1980 BMW R100RS 78.0R 85.0R Stock original

980 cc ohv 2 cyl 78.0 L 86.0L m/c.

full fairing, Krauser cases

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1948 Vincent Meteor 86.0 94.0 pattern silencer

500 cc ohv 1 cyl. engine“Comet”

spec. S.

1988 BMW R100GS 78.0 83.0 standard ex.

980cc ohv 2 cyl Dual sport

model. m/c.

2000 Triumph Thunderbird 77.0R 85.9R 98.6R Triumph “off-

900 cc 3 cyl, ohv w/c 77.1L 86.0L 99.0L road” ex. m/c.

1982 BMW R100R 79.0 94.5 (3K) 97.0 2-into-1 with

980 cc 2 cyl ohv “Super Trapp”

silencer. m/c.

1977 Yamaha XS650 74.1R 86.5L Stock ex. m/c.

650cc ohv 2 cyl 74.1L 86.5L

1968 Honda 65 71.0 86.1 Stock silencer

65cc 4 stroke single S.

1975 Kawasaki Z1 83.0R 86.0R 100.1R Restored stock

900cc 4 cyl 4stroke 83.0L 86.0L 99.1L m/c.

1980 BMW R100T 74.2R 85.9R Stock ex. m/c

980 cc 2 cyl 4 stroke 74.6L 86.2L

1977 Honda Super Sport 76.1 83.2 96.0 Original ex.

400 cc 4 cyl ohc 4-into-1 m/c.

1975 Ducati 750GT 86.0R 94.3R Stock ex.

750cc ohc 2 cyl. 85.5L 94.2L m/c

1937 Indian Dispatch-Tow 82.1 90.6 Stock Ex.

750 cc v-twin side valve fishtail exit

3 – wheeler under body.S.

1942 Indian Scout 91.9 106.0 “Brooklands”

800 cc from 500cc v-twin “Can” with

side valve fishtail. S.

1940 Indian Scout 86.1 95.5 Standard

800 cc from 750 cc v-twin Indian “Chief”

side valve ex. system. S.

1940 Indian Scout 80.2 93.1 Standard

750 cc v-twin side valve Indian “Scout”

ex. system. S.

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1971 BSA Rocket 3 83.8R 90.1R 94.3R Stock ex. sys.

750 cc ohv 3 cyl 4 stroke 83.8L 90.1L 94.0L m/c

1968 BSA 650 “Chopper” 89.3R 90.9R Straight pipes

650 cc 2 cyl 4 stroke 89.1L 90.6L no silencers

“half washer

welded inside

each pipe.” S.

2000 Harley-Davidson 87.0R 90.1R Vance & Hines

“Classic Special” 87.1L 90.2L “Monster Oval”

1700 cc v-twin 4 stroke 49 state legal

aftermarket

m/c.

1913 Rudge “Multi” 84.0 95.6 expansion box

500 cc single Ioe 4 stroke with straight

short, small

dia. Outlet

original pattern

Restored. S.

1925 Henderson DeLuxe 89.3 98.4 baffle on

1200 cc 4 cylinder 4 stroke (max. rpm) expansion box

closed. Short

tail pipe. R/H

sidecar reflecting

sound. S.

1924 Sunbeam Model 6 TT Replica 86.5 95.2 Stock TT ex. pipe

500 cc side valve 1 cyl. racing type length

can be adjusted

for tuning. S.

1914 Douglas 4 hp flat twin 92.7 98.0 Expansion box

600 cc 4 stroke short, small dia.

Ex. pipe. S.

1927 Zenith 680 sv JAP engine 88.6 95.2 short silencer. S.

680 cc 2 cyl. 4 stroke

1970 Hodaka Ace 72.0 86.5 Stock exhaust. S.

100 cc 2 stroke single cyl.

1936 Francis-Barnett Power Byke 79.4 94.8 Stock exhaust. S.

98 cc 2 stroke single cyl.

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1946 Mobylette Moped 80.4 91.2 Stock exhaust. S.

50 cc 2 stroke single cyl.

1934 Francis-Barnett Cruiser 45 89.0 96.0 Cast expansion

250 cc Villiers 2 str, 2 port,1 cyl chamber single ex.

pipe no silencer &

fishtail. S.

1961 Honda C77 Dream 72.2R 86.1R Stock ex. sys.

305 cc ohc 2 cyl 4str. 72.1L 85.9L reproduction. S.

1967 BSA Royal Star 82.4R 93.0R Stock ex. sys.

500 cc ohv 2 cyl 4str. 82.5L 93.1L Restored. m/c.

1972 Norton Commando 80.1R 91.8R Stock pattern

750 cc 2 cyl 4 str. 79.9L 91.7L ex. sys. m/c.

1971 Triumph 250 TRW 80.0 90.7 Sammy Miller

250 cc 1 cyl. 4 stroke Trials trials type mini

silencer. S.

1926 Scott Super Squirrel 91.8 100.0 expansion box

500 cc 2 cyl. 2 stroke w/c and short small

dia. pipe. S.

1951 Moto Guzzi Falcone 82.8 96.0 Stock Guzzi

500 cc 1 cyl 4 str. Silencer. S.

1984 Yamaha XJ750 79.0 92.0 101.4 Home made can

750 cc 4 cyl 4str. Silencer. m/c

1940 Indian 4 77.0 93.0 (max rpm) Stock Indian

1300 cc 4 cylinder, 4 str. 4-into-1 ex. pipe

S.

1967 Triumph Bonneville 80.2R 93.5R Stock ex. sys.

650 cc 2 cyl 4 str. 80.3L 93.5L restored. m/c

1979 Yamaha SR500 80.5 94.5 baffled “café

500 cc 1 cyl 4 str racer” style

exh. m/c.

1937 Rudge Sports Special 84.0R 92.9R 2 high level

500 cc 4 valve 2 port 1 cyl 4 str 84.1L 92.9L pipes. 2 silencers

4 valve engine.S.

1982 Kawasaki LTD 250 76.0 84.0 Stock ex. sys. m/c.

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250 cc 2 cyl 4 str.

1968 Velocette Venom Clubman 83.0 92.6 Stock Velo ex.

500 cc ohv 1 cyl 4 str pipe & silencer

built-in fishtail.

m/c.

1970 Norton Commando Roadster 83.0R 94.1R “Daytona” pattern

750 cc 2 cyl 4 str. 82.9L 94.5L silencers, not std.

Replicas. m/c.