Hello,
I've nearly finished restoring my 1942 WM20 and am doing my best to avoid buying a noisy aftermarket "straight-thru" silencer that everyone makes these days.
Does anyone have a photo or a technical drawing of the inside of a genuine BSA wartime silencer, so I can make one myself. Any help welcome.
Cheers,
Steve, Malta.

email (option): szerafa1@gmail.com

Hi Steve,

I have just send you some photos.

Henk

email (option): ahum@quicknet.nl

Suprisingly the Original M20 silencer is completely hollow, but very silent. the two pipe on both side run for only a short distance inside the body.

These are the remains of the frontside.





I believe the rear has a sort of valve fixed at around 45 degrees.

What pictures do you have, Henk? curious about them, Cheers, Michiel

email (option): m.wijbenga@hotmail.com

Simple way to make an efficient but quiet muffler.
Weld around 12" to 18" on to the end of your exhaust pipe.
Weld a washer to the open end about 1/2" inside the open end.
Mark 3 spiral lines along the length from the clamping point to the washer you welded in so that they are equal spaced and make 1 full revolution of the pipe.
Now drill along these lines, starting from 1/8" to 5/8" in increasing sizes from front to back.
This is now a perminant baffel that will not choke the engine but it will break up the wavefronts and spiral the exhaust gas flow.
Whatever you put over the top will just be window dressing.
This was a common practice in the 20's 30's & 40's
The WD B40/C15 use a short version of this and they are inaudiable at a distance of 1/2 mile in open space (part of the design brief of the Aust spec ones )

email (option): bsansw1@tpg.com.au

Here is an original tipped up silencer that Steve Madden gave me a few years ago. I've just cut the end caps off to expose the baffles. There's nothing in the middle. Ron


upload full resolution photos



upload high quality photos

email (option): ronpier@talk21.com

Thanks Ron, very clear.

I have an orginal one on my M20, it is very silent, and it amazes me that only this hollow tube will take up so much noise.

BR, Michiel

email (option): m.wijbenga@hotmail.com

Ron...The left hand half of that baffle has an additional piece fitted in the end....Could you show that 'end on' or from an angle to show the detail of that part more clearly?....Ian

email (option): ian@wright52.plus.com

Yep I've bunged it back in the container for now, but can easily take more detailed pix tomorrow. Ron

email (option): ronpier@talk21.com

This to add to my previous pictures.
The dimensions are as follows:- OD of rear tube = 1 13/16" (46mm) length of tail pipe = 3" (76mm) length of baffle = 6 1/2" (165mm)

The front pipe is 2" (50mm) OD and the bit that is squashed like a reed valve is 3 1/4" (82.5mm) long. Ron

email (option): ronpier@talk21.com

Thanks Ron...Ian

email (option): ian@wright52.plus.com

I could ask Armours if they would make an exact copy of this silencer if anyone is interested. Ron

email (option): ronpier@talk21.com

I'd be interested if it was in stainless, subject to final cost of course...

I have a brand new 'standard' Armours silencer sat on the shelf though..Ian

email (option): ian@wright52.plus.com

Overlander already make M20 mufflers in stainless and Barry will put any baffle you like in there
http://dropbears.com/overlander/
Make you a matching M20 exhaust pipe in stainless as well.
A couple of my bikes are running his systems.
The A65 has decibel copies complete with tuneable outlets which have been on it since 1992

email (option): bsansw1@tpg.com.au

Shipping from Australia to UK or Europe would be expensive and in the UK we get stung for customs duty.

email (option): Horror@blueyonder.co.uk

Ron your wife is going to kill you when she sees the state of her new table cloth.

email (option): deepsea@vol.net

that's a good one!

email (option): ronpier@talk21.com