Motorcycle 'slip-on' exhausts

[GuzziHero]

My Guzzi Griso has an MHP exhaust and I messaged the makers to ask what its dB level might be as I am planning to take it on a trackday. He says he doesnt know, he has no data on that bike model.

 

Does this mean that you could put pretty much ANY exhaust on ANY bike? Seems odd that the Griso has a silencer that wasnt designed directly for it!

 

Odd!

[Stealthbomber]

Long as the can will fit over the tube then yeah, it should work.

 

The actual law on silencers is kinda convoluted (to the point where I'm probably wrong about some of it) so for a can to be E-marked (and, thus, road legal) it's supposed to be "tamper-proof".

 

I'm not completely sure if pop-rivets count as being "tamper-proof".

Obviously, we've all heard of people dismantling a can, removing the baffles and then rivetting it back together again but recently it's become popular for people to have their silencers "cored" which means, basically, paying somebody to shove a stonking great hole-saw right the way through your silencer to create a big hole straight through it.

I think the popularity of this rather rough procedure is because rivetted cans aren't strictly road-legal any more.

 

I mention all this cos a mate of mine has modified a 125 silencer so it'll fit onto his R1!

Basically, he drilled out the rivets, removed the ends and fitted ends from an R1 can then cobbled it all back together again so he's left with a tiny little can only about 1" wider than the pipe AND, importantly, the body of the silencer still has an E-mark sticker on it. Hmmm...

 

Course, the R1 needs all the help it can get. It might be quick but it sounds like a food mixer on crack when you twist the throttle.

There really IS only one company who makes truly bonkers sounding bikes and the name starts with a "D" and ends with a "ucati".

 

FWIW, my bike is fitted with Termignoni Zorsts and they really ARE loud enough to make kittens explode and women cry.

I checked them with a calibrated industrial noise meter prior to a track day and they're dead on 95dB, which is the limit for most tracks.

 

Basically, if your Griso doesn't make a noise that makes you feel like you want to evacuate your bowels if you rev it in your garage then you should be okay.

 

If you're at all worried you should find a friend who owns an iPhone, tell em to download a free decibel meter and use it to test your exhausts from a range of about 1 metre.

Cos the iPhone uses standardised parts it's quite easy for developers to write software to monitor sound accurately.

[Spudgun]

I mention this for what it's worth (I found it completely by accident last month when I was looking for something else). The rules relating to silencers changed a few years ago. I can't remember the exact wording, so I'll summerize.

 

Exhaust systems no longer require markings of any kind (BSAU, Makers mark, nothing).

The noise emmited from the exhaust must not (In the MOT testers opinion) be 'out of character' for the machine in question. So if you've got a Yamawaki Velly Fast Indeed, it can't sound like a Harley. If you've got a Kawasaki W650, it can sound like an old British bike.

 

I should point out that this applies to the UK only. I have a friend who has a Ducati. He only puts the mutes in for the MOT and he still has the original exhaust system. As for my Enfield, it only has "Royal Enfield" stamped on the end of the silencer. Still noisey though.

[GuzziHero]

I dunno...most Harleys with open pipes are OBNOXIOUSLY loud! The Griso is meaty but a little muffled, but I like it that way.

 

As for 'out of character'...I wouldnt say that the latest R1 sounds in character. A straight-4 which sounds like a poorly 2-stroke V-twin...