Commando exhaust chirping

baz said:

I may have asked this question before so apologies if I have
But back in the day a lot of commandos used to chirp/Twitter when fitted with pea shooters
Nowadays they don't, or I don't hear it any more?
But when I have a colour tune fitted to my commando it twitter's like a goldstar!! It's a really loud Twitter
What difference does the colour tune make?
Maybe it's the position of the electrode?
Or the value of the colour tune is way different to the spark plug value?

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Tornado said:

Been researching the chirping with the Google machine and it seems this is not an uncommon problem across many different bikes. Some KLR's cure it by bashing a big screw driver through the internal baffles on the exhaust. A V-twin cured a chirp on one side by slightly changing how far the silencer was pushed over the header pipe...effectively changing the exhaust travel length (so "tuning" it out).

What is the sound from? Just some sonic whistle due to the pressure pulse or something from the valves or rockers?

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