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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Decibels from a hot Comet
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<blockquote data-quote="Pete Appleton" data-source="post: 13530" data-attributes="member: 145"><p><strong>Noisy Exhausts</strong></p><p></p><p>Phil</p><p> The first answer is 'no' you don't get any allowance on noise levels for an old engine, although you do get an exemption on exhaust emissions.</p><p></p><p> I am currently building a 600 with Gary Robinson '105' cams that will also need to meet SVA. With a modern silencer from a 500cc Honda the exhaust noise is well below the limits, although I can't remember exactly what the reading was. </p><p></p><p>My only worry at the moment is the mechanical noise from the engine. With a proper, modern, silencer the exhaust note is very muted but if you put the dB meter alongside the engine you get a spectacular reading. Fortunately for the test the dB meter is placed 1m behind and 1m to one side of the tailpipe. I am waiting to see what happens to the engine noise once the bodywork and panniers are fitted. It is possible that some form of sound deadening may be needed around the engine sides.</p><p></p><p>Clearly, once the test is over the sound deadening goes in the bin and a far more interesting silencer goes on.</p><p></p><p>The other thing to bear in mind is that on the SVA application form you are asked to specify the maximum revs for the engine. The sound test is conducted at 3/4 of the maximum speed! If you specify a very low maximum revs and put a suitable red line on the tacho then that may help.</p></blockquote><p></p>
[QUOTE="Pete Appleton, post: 13530, member: 145"] [b]Noisy Exhausts[/b] Phil The first answer is 'no' you don't get any allowance on noise levels for an old engine, although you do get an exemption on exhaust emissions. I am currently building a 600 with Gary Robinson '105' cams that will also need to meet SVA. With a modern silencer from a 500cc Honda the exhaust noise is well below the limits, although I can't remember exactly what the reading was. My only worry at the moment is the mechanical noise from the engine. With a proper, modern, silencer the exhaust note is very muted but if you put the dB meter alongside the engine you get a spectacular reading. Fortunately for the test the dB meter is placed 1m behind and 1m to one side of the tailpipe. I am waiting to see what happens to the engine noise once the bodywork and panniers are fitted. It is possible that some form of sound deadening may be needed around the engine sides. Clearly, once the test is over the sound deadening goes in the bin and a far more interesting silencer goes on. The other thing to bear in mind is that on the SVA application form you are asked to specify the maximum revs for the engine. The sound test is conducted at 3/4 of the maximum speed! If you specify a very low maximum revs and put a suitable red line on the tacho then that may help. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Decibels from a hot Comet
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