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dB Meter test/noise reduction.

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I was concerned about my stock IT250J passing the new noise level limit of 94dB for recreg. My suspisions were confirmed when I purchased a noise level meter. My test was done on a static bike in a closed 155 square metre factory of concrete slab construction. Bike was propped upright on the ground. Readings were taken at waist level from a distance of 2m (6ft). Four readings were taken for each subsequent modification, from 1. chamber side, 2. the rear, 3. clutch side, 4. front. All figures were rounded up to the next full dB figure.

Stock:

1. 101dB

2. 94dB

3. 100dB

4. 92dB

Addition of fibreglass header gasket:

1. 96dB

2. 92dB

3. 94dB

4. 90dB

Addition of two extra barrel fin dampeners and one extra head fin dampener:

1. 94dB

2. 91dB

3. 92dB

4. 90dB

Addition of fibreglass heat wrap:

1. 90dB

2. 89dB

3. 90dB

4. 88dB

1headerwrap.jpg

2chamberwrap.jpg

3quieter.jpg

Hope this is of benefit to your neighbours, local authorities and your ears.

Cheers,

Chrisko.

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Hey neat post. What's a head barrel dampener?

Shrub,

If I'm not mistaken, those would be the rubber pieces that bridged the gaps of the cooling fins on the jug and head. The idea was to reduce vibration and thus noise. I've seen a lot of old air-cooled smokers that have been missing those things. Air cooled bikes are loud enough with them.

I actually made some for my old YZ490 out of an old semi mud flap. They did help reduce vibration a little, but I couldn't telll if the noise was dampened any.

Wish I had tried the pipe wrap though. I am certain that would have made a bigger difference in the sound levels and vibration of that beast.

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...If I'm not mistaken, those would be the rubber pieces that bridged the gaps of the cooling fins on the jug and head. The idea was to reduce vibration and thus noise. Air cooled bikes are loud enough with them.

I actually made some for my old YZ490 out of an old semi mud flap. They did help reduce vibration a little, but I couldn't telll if the noise was dampened any.

I would cut little sections of rubber gas hose to wedge between the cylinder fins on BSAs and Triumphs. They made a noticable difference in quieting valve clatter. :smirk:

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I remember riding my BMW momentarily without my helmet on, first time I'd heard the motor working in ages, thought something was broken until I realised no helmet on.....

I have had this wrap on my DR650 for a year now, it makes a little difference. Spraying sound deadener on the inside of the bashplate was a handy tip I picked up too.

whitewrap.jpg

Cheers,

Chrisko.

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