Swm Rear Silencer.

[john.b]

Restoring a 240 Swm and the rear silencer box was full of the usual crud and also the the two baffles had come loose virtually blocking the way out for the exhaust gases. Is it best to reweld the baffles back in to their original positions or can you leave them out to let the engine breathe easier? Thanks.

[collyolly]

I would try to keep it original, the design is to partly keep the noise down and partly to maintain a back pressure to make the engine work properly.

The manufacturer put it in there for a reason after all !

[pschrauber]

The noise reduction system of the rear silencer is based on the Helmholtz principles using different volumes' and different sizes of tubes. As it is constructed now it works for all noise levels that comes from the engine. You can leave the system too as it is as build up crud can't effect it much.

Anyway the rear silencer build up a permanent resistance of "air pressure" against the complete exhaust system that is mounted before the "chambers" and tubes. Thus providing less noise but too restricts the performance here the build up of motor revs., one of other reasons the bikes with this era and silencer react/respond so slow to throttle.

If you want that the bike react faster but deliver as less noise take out all baffles and tubes and place a hole tube instead through the complete silencer. The diameter around 25mm. Then fill the hollow between the hole tube and the rear silencer well with insulation, the modern stuff works best mineral insulation less good.

But the insulation will soak up oil residue and after a time your bike will sound louder and you have to replace the insulation (the backdraw) but the engine will respond better (the benefit).

Now it's up to you?

Edited February 20, 2016 by pschrauber

[htrdoug]

The noise reduction system of the rear silencer is based on the Helmholtz principles using different volumes' and different sizes of tubes. As it is constructed now it works for all noise levels that comes from the engine. You can leave the system too as it is as build up crud can't effect it much.

Anyway the rear silencer build up a permanent resistance of "air pressure" against the complete exhaust system that is mounted before the "chambers" and tubes. Thus providing less noise but too restricts the performance here the build up of motor revs., one of other reasons the bikes with this era and silencer react/respond so slow to throttle.

If you want that the bike react faster but deliver as less noise take out all baffles and tubes and place a hole tube instead through the complete silencer. The diameter around 25mm. Then fill the hollow between the hole tube and the rear silencer well with insulation, the modern stuff works best mineral insulation less good.

But the insulation will soak up oil residue and after a time your bike will sound louder and you have to replace the insulation (the backdraw) but the engine will respond better (the benefit).

Now it's up to you?

  

 

 

 

MX silencer 25mmx250mm long really woke up my 320TL,not really loud,has beefy sound. I did really like the quietness of the stock system,If just trail riding I would stick with quiet. 

[turbohead]

In the '80s some manufacturers tried this kind of solutions, but nowadays you don't see them at all as they simply destroy the low end torque of the engine. All later bikes rely on a design as outlined above and you can both keep the looks of your SWM and get better rideability by just modifying your silencer. If you don't care about that '80s look, just make a suitable mx silencer fit your bike or buy one of the aftermarket replacements for your SWM. Some welding is needed if you don't buy a replacement, but that is almost like therapy at this time of the year. It is easy to just cut off the end of your silencer and make that part detachable together with the new core tube when replacing the insulation.

[john.b]

Thanks for the quick replies, really appreciate the help.

[bezaboy]

Contact Martin at WWW.MotoSWM.COM 

Well worth a chat as he has both this type and after market kit.

[brownie001]

I tried this Giannelli on my 125 for a while. I liked it, was a little louder than the standard box and I felt that the motor was a bit livelier. Now have the standard box back on as too many people past comments regarding the modern looks and the noise.