Decibels from a hot Comet

Howard

Well Known and Active Forum User
VOC Member
Has anyone tried a Harley silencer? I don't know anything about them, but I've noticed a few with very small after market silencers that seem to run very quiet (for a lumpy vee twin).

In answer to the original question ... "a lot". My racing comet with Mk IIs and a short tuned 1 5/8" pipe (or was it 2"?) was off the scale on the noise meter in the 80s (and I didn't actually take it up to the right revs). Luckily it was VOC Cadwell and Jaqueline Bickerstaff had the meter, so I sneaked out. After that it was hard work keeping the power and losing the noise. I could never understand why some simillar sized bikes on open pipes were so much quieter than the Comet.

H
 

nobby

Well Known and Active Forum User
VOC Member
size is not important?

Has anyone tried a Harley silencer? I don't know anything about them, but I've noticed a few with very small after market silencers that seem to run very quiet (for a lumpy vee twin).
H

My 2" Supertrapp is the same as another Vincent owner in my hometown used for his Harley Lowrider, only he had two of them.

By the way: my wife is looking here for a mirror, I changed it from left to right when we visited Scotland... She was already confused because whe had a weekend without breakdowns!
 

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Howard

Well Known and Active Forum User
VOC Member
My 2" Supertrapp is the same as another Vincent owner in my hometown used for his Harley Lowrider, only he had two of them.

By the way: my wife is looking here for a mirror, I changed it from left to right when we visited Scotland... She was already confused because whe had a weekend without breakdowns!


That looks very tidy, is it quiet? ............................ The silencer, not your wife, that is.

H
 

nobby

Well Known and Active Forum User
VOC Member
quiet?

It is NOT quiet. I can compete with those ' persons' on japanese and americain apehangers who leave their silencers at home. You know what a terrible noise some of those guys can make.
So I am looking for a more silent replacement.
I am still talking about the Supertrapp!
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Supertrapp

Hello howard,
I think you can tune the Supertrapp to make it quiet by taking plates out,
Or putting them in, Is that right Nobby ?.
I saw one in a shop the other day, Trouble is you will loose power ?.
If it was me I would leave the end off, where I live even the cars have
6'' end exhausts, I spoke to the local car MOT man and he says he has to pass them !!.
They are very expensive, But I like Nobby's idea of a 2" pipe + Supertrapp,
I have a 2" front pipe off the Lightning I could use !!.
If I ever get a 600cc built, That is the way I would like to go !.
All the best Bill.
 

nobby

Well Known and Active Forum User
VOC Member
Hello howard,
I think you can tune the Supertrapp to make it quiet by taking plates out,
Or putting them in, Is that right Nobby ?.

Yes you can tune them with plates for sound but more important for power! Peter Volkers is using a normal Vincent diameter Supertrapp and he won several horsepowers on a Dyno. With the 500 I rode with an open cone (like on the picture in this thread), but later I discovered that with a closed endplate the riding on the 600 was nicer and more smooth through all revs. I am not an expert in this, but maybe the same reason that megaphones are not a good solution for Comets?
 

Howard

Well Known and Active Forum User
VOC Member
Hello howard,
I think you can tune the Supertrapp to make it quiet by taking plates out,
Or putting them in, Is that right Nobby ?.
I saw one in a shop the other day, Trouble is you will loose power ?.
If it was me I would leave the end off, where I live even the cars have
6'' end exhausts, I spoke to the local car MOT man and he says he has to pass them !!.
They are very expensive, But I like Nobby's idea of a 2" pipe + Supertrapp,
I have a 2" front pipe off the Lightning I could use !!.
If I ever get a 600cc built, That is the way I would like to go !.
All the best Bill.


Hi Bill

This is just curiosity for me. I've used a Dunstall Decibel (copy now) on the Egli since the 70s, it seems to suit the engine and it gives a nice bark that other road users notice. No one's ever said "Sorry mate, I didn't hear you."

H

ps One club member says it should be called an amplifier not a silencer.
 

Howard

Well Known and Active Forum User
VOC Member
Yes you can tune them with plates for sound but more important for power! Peter Volkers is using a normal Vincent diameter Supertrapp and he won several horsepowers on a Dyno. With the 500 I rode with an open cone (like on the picture in this thread), but later I discovered that with a closed endplate the riding on the 600 was nicer and more smooth through all revs. I am not an expert in this, but maybe the same reason that megaphones are not a good solution for Comets?

Hi Nobby

I don't know the theory, but it was "known from experience" (I don't know who's experience or when) that Vincents didn't run best on megaphones. I tried one for a very short time, and, if I remember right, it caused flat spots all over the rev range.

On the track, I used a straight 2" pipe that reached the RFM pivot (not the wheel spindle) I was laughed at when I arrived at the VOC Cadwell meet, but after the first practice, several Comet riders were seen with hacksaws. Everyone knows a racing Vin exhaust should reach the rear wheel spindle, but what was forgotten was that the rules of the day (50s) said that the exhaust had to be at least that long. My memory fades a bit at this point, but I think the standard length pipe is tuned for about 4000 rpm, which would mean it was also good at 2000 and 8000 rpm, mine was calculated for 6000 rpm (ish) which was closer to where I was revving. All incidental now, as it would not be allowed on the track with that setup.

H
 
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