Original mufflers? -How to tell?
- Thread starter Johnnymac
- Start date
- Status
- Joined
- Dec 28, 2009
- Messages
- 5,467
I sure miss the twittery sound on backoff throttle. Yes , I remember the internals looked like a shark's gills.
- Joined
- Oct 19, 2005
- Messages
- 18,978
On the 6 th day of my 1st Commando I was heading to ride with locals and when I got there they said they knew it was me from couple miles a way as i came down the slope on trailing throttle. There was another hopped up Commando among the HD crowd with familiar sounding silencers they all approved of. Will we ever hear it again?
I drew the original "reverse cone" mufflers and was peripherally involved in the noise testing. At the time, 1970, the hardest noise limit to meet was for California and that was quite a bit quieter than anywhere else. To meet the California rules the silly little insert was inserted and retained by a self tapper, obviously not intended for a long life.
Anyway, from memory the full length tubes with the so called triangular perforations ran full length and were straight through. This was wrapped in one layer of perforated metal which was supposed to stop the fibre glass wool, that was packed over the perforated metal, blowing straight out the back. All the seams were flush.
The testing involved incredibly boring passes by the noise meter accelerating in second or third gear, I forget which, from one speed to a finishing speed. The laid down testing procedure was very specific. The testing was best done on a calm day to avoid spurious readings, and was done on an old airfield to avoid echoes or reflected noise. All of which makes me wonder about "rules" when you are passed by an HD making enough noise to make your ear drums meet in the middle and hardly accelerating at all.
I know that these mufflers were replaced by the seamed ones, but I don't know what they were like internally. I imagine that it was for cost reasons.
The testing demonstrated that induction noise was at least as big a problem as exhaust noise. I think that was one of the reasons for the lengthened side panels later on...
Hope this helps
cheers
wakeup
Anyway, from memory the full length tubes with the so called triangular perforations ran full length and were straight through. This was wrapped in one layer of perforated metal which was supposed to stop the fibre glass wool, that was packed over the perforated metal, blowing straight out the back. All the seams were flush.
The testing involved incredibly boring passes by the noise meter accelerating in second or third gear, I forget which, from one speed to a finishing speed. The laid down testing procedure was very specific. The testing was best done on a calm day to avoid spurious readings, and was done on an old airfield to avoid echoes or reflected noise. All of which makes me wonder about "rules" when you are passed by an HD making enough noise to make your ear drums meet in the middle and hardly accelerating at all.
I know that these mufflers were replaced by the seamed ones, but I don't know what they were like internally. I imagine that it was for cost reasons.
The testing demonstrated that induction noise was at least as big a problem as exhaust noise. I think that was one of the reasons for the lengthened side panels later on...
Hope this helps
cheers
wakeup
- Joined
- Jan 23, 2010
- Messages
- 675
No, the induction noise problem was done away with by introducing the plastic air filter which came together with the beancan silencers ("A" models).
The bigger side panels went with the Interstate tank and I doubt a plastic or sheet metal panel makes any noise difference. In which case only the Interstate models were more quiet...
Internally all "Roadster" silencers are the same. I believe the seam was not polished out later for cost reasons. Our seamless silencers are dearer in manufacture, hence in RRP. Internally they are identical to the ones with the visible seam.
Joe/Andover Norton
The bigger side panels went with the Interstate tank and I doubt a plastic or sheet metal panel makes any noise difference. In which case only the Interstate models were more quiet...
Internally all "Roadster" silencers are the same. I believe the seam was not polished out later for cost reasons. Our seamless silencers are dearer in manufacture, hence in RRP. Internally they are identical to the ones with the visible seam.
Joe/Andover Norton
ZFD said:
Is that current roadster mufflers are all the same.
Or are we talking back when these Commandos were new in showrooms ??
Which is obviously not the case. Clarification needed. ?
BTW, I had a BM twin that had been fitted with a pair of shorty trail bike mufflers.
It tweeted on the over-run, probably more than peashooters did, but quieter.
They had a small bore perforated central tube, and fiberglass wrapping.
Dealer was fascinated when they took it for a test ride.
- Joined
- Dec 28, 2009
- Messages
- 5,467
Back -when new. With the back-off tweeting.
ZFD said ".....No, the induction noise problem was done away with by introducing the plastic air filter which came together with the beancan silencers ("A" models)."
Fair enough, sorry for being misleading. I do have a memory of a discussion about the induction noise and long side panels though, maybe the issue was filed away and resurrected at a later stage.
About the twittering mufflers. I had a pair of Commando reverse cone mufflers on my Honda 500/4 (it had a 4 into 2 exhaust system), it sounded fantastic and it twittered. Until all the fibre glass wool disappeared when it just sounded fantastic.
cheers
wakeup
Fair enough, sorry for being misleading. I do have a memory of a discussion about the induction noise and long side panels though, maybe the issue was filed away and resurrected at a later stage.
About the twittering mufflers. I had a pair of Commando reverse cone mufflers on my Honda 500/4 (it had a 4 into 2 exhaust system), it sounded fantastic and it twittered. Until all the fibre glass wool disappeared when it just sounded fantastic.
cheers
wakeup
- Status
