poor quality repop silencers

Jez Nemeth

Well Known and Active Forum User
Non-VOC Member
If Armourers still do a stainless silencer, that will fit a Comet, shape, size, bore and is open, or openish?

Then there might be a New, totally unused Chrome Armourers silencer available to one lucky interested party...Normski, this could be your lucky day! ;)
 
Last edited:

Magnetoman

Well Known and Active Forum User
VOC Member
For what it's worth, this week I measured two new, aftermarket Burgess-type silencers on my flow bench:

Burgess-type #1, 90.9 CFM
Burgess-type #2, 184.4 CFM

For comparison, an OEM semi-megaphone from a Clubman Gold Star flows 186.5 CFM (all measurements at a pressure of 20.4" H2O). I don' t know what either sounds like but I suspect there might be a difference. I know there would be a difference in the h.p.

Two years ago I put a new shorty silencer on my Catalina Gold Star, but initially it ran horribly. The problem was revealed when I removed the air box and saw a cloud of fuel at the inlet of the carburetor, ejected by too-much back pressure from the new silencer coupled with large valve overlap. The cloud enriched itself as it passed over the spray tube on the way out, and enriched itself even further when sucked back in. Drilling a number of holes in an internal baffle fixed the problem.

Related to this, even with the restrictive silencer the bike ran fine when the air box was off (at least when revving it on the driveway), apparently because enough fuel was able to escape from the cloud so as not to be extraordinarily rich. Before I discovered the problem and drilled the holes my wife commented that the bike didn't sound right.

The exhaust system flow does affect the h.p. but it's not a simple tradeoff of h.p. vs. decibels. The frequency spectrum matters to how annoying it is, and some do a much better job than others in killing the offending tones without restricting the flow too much.
 

vibrac

Well Known and Active Forum User
VOC Member
I have a decibel meter since for racing and parading you have to be under 105Db at most circuits. (annoyingly the one just up the road is 85Db -drive by! I dont think a Firefly would pass that.
Anyway on the Flash its difficult to get a small silencer that looks unobtrusive on a two inch pipe and racing cams working on the basis that thin walls in houses let noise through, I got some 3" internal alloy tube with 1/4" wall and turned two end caps also with 1/4" walls and 2" inlets outlets and fitted a two inch perforated tube (car exhaust component part) flared at inlet to take the main pipe. This runs through the body with the 1/2" annular space filled with packing. result? heavy, but all bolted up it gives 105-6 Db and is small enough not to interfere with the paddock stand. In more enlightened surroundings (like the flywheel festival) I have an simple open pipe extension
 

Jez Nemeth

Well Known and Active Forum User
Non-VOC Member
To add to the mix and confirm - the Armourer's Chrome silencer is pretty much straight through -taken the best shot I could to show this, apologies if it looks like an entry to an abstract photo competition, but hey ho... On the B side, a big note of caution here, this exhaust is NEW and has been sitting wrapped in a dry garage for the last year, pulled it out and the chrome finish on the near side (bike side facing) has broken through in places and showing signs of pitting through the chrome along its length, terrible quality Chroming. I have a Suzuki pipe sitting close by, original 1981 and its perfectly fine & unwrapped . . . Photo 2 . . . unimpressed is an understatement :(
 

Attachments

  • Armourer's.jpg
    Armourer's.jpg
    305.9 KB · Views: 50
  • image-4.jpg
    image-4.jpg
    242 KB · Views: 49

Bill Thomas

Well Known and Active Forum User
VOC Member
So it just has a baffle plate across the hole ?, They didn't have that on the Stainless ones,
Hope they still don't !.
I will go down there in the next week or two. Cheers Bill.
 

BigEd

Well Known and Active Forum User
VOC Member
VOC Forum Moderator
So it just has a baffle plate across the hole ?, They didn't have that on the Stainless ones,
Hope they still don't !.
I will go down there in the next week or two. Cheers Bill.
I've got an Armour's stainless silencer on my Rapide. It is a straight through design. I bought it a few years ago but didn't fit it until last year. The quality seems pretty reasonable and it hasn't gone rusty. ;)
 

Jez Nemeth

Well Known and Active Forum User
Non-VOC Member
I'm heading for a Stainless one as intended, baffling is quite light -but certainly love to bring the state of this chrome one to their attention -quality is very poor if its doing that, a last thing Friday afternoon silencer. . .
Bill, be interested in what you find down there, heading that way myself day after the Severn Glos Rally -Windsurfing with the kids at Poole, then on to Bridport/Weymouth for a few days...so Bournemouth is on route. Might just take that chrome exhaust with me after the Rally..oh yes.
 
Last edited:
Top