Rejetting.

I bet your neighbours are going to love you! 

I cannot understand the fascination of noisy pipes - makes a ride of any distance  more tiring, attracts unwanted attention and generally pisses 'non enthusiast' people off. Aren't the standard pipes noisy enough?

Just what are the positives other than a couple of bhp at max revs?

Just saying.

George 

There should be more than enough adjustment in the carbs you have, though you don't say whether this is 750 / 850 and where you currently are with the jets currently fitted. Fit the silencers and dyno it then you can tell precisely what is happening

We dyno'd some silencers with various fillings and the straight through type were not always the loudest, like wise the quietest silencers were the most powerful, On both bikes the Premiers metered perfectly and had adjustment available if needed.  

Most Dyno's are relatively cheap for an hour or so and really do tell you a lot other power and torque, get the operator to check the fueling response at gear changes. if you have issues it will show there first.  

I remember those “whistler pea shooters” also They were fitted to some 750 Commandos.

A number of years ago I fitted the Armours version of the Commando peashooter silencers to my 850, they had the perforated mesh you describe.

No re-jetting required, the bike ran fine but extreme noise on open throttle under load.

I now have the more sociable standard Andover peashooters fitted which are easier on the ears!

When new my 1974 Commando Roadster had the whistle and chirping noise you talk of, the original silencers had fluted tubes and were packed with sound deadening material between the tubes and outer silencer.

The sound deadening material seemed to absorb dampness and rot the silencers from the inside out.  

I think Andover offer a similar original spec silencer now, but hopefully it's without the corrosion problems

... on the over-run when you shut the throttle - like the BSA Gold Star DBD34 "twitter" ...