PT: Exhaust Comet silencer

Bill Thomas

Well Known and Active Forum User
VOC Member
Has anybody put a Road ish, Comet on a Dyno', I would be interested in knowing how long the silencer should come out the back.
I proved many years ago with my Blue Twin, That it can make a lot of difference.
On a 1/4 mile sprint, I had 2 pipes ending at the rear wheel spindle, Brother Ron welded 2 . 6" extensions,
It ADDED a second to my times, I then sawed 3" off each pipe, Got half a second back !, Then went back to the Wheel spindle and got my times back to normal.
I have seen silencers ending in line with the wheel rim and some the back edge of the tyre.
I have seen a photo of John E. Of fork Fame, With his sticking out the back a lot more !!.
I think, There is Power to be found or lost !!, Just because of a few inches, But it must look right for the Road !,
So no silly short pipes that some used in Racing many years ago.
Cheers Bill.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Modify modify....
Modify modify et al.... What like this?? LOL

It started out with about 6 holes in total and a solid end cap!

Still chokes performance compared to a straight pipe.

baffle 1.jpg
baffle 2.jpg
baffle 3.jpg
 

Bill Thomas

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VOC Member
Just been out on my 2015 Comet, With a new Armours, Stainless Steel down pipe, And a standard length, Armours, S/S Silencer, Never been as quiet !, As I said before, I sawed a few inches off the tail pipe, On my other Silencer, I thought it made it more loud !. Cheers Bill.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Just been out on my 2015 Comet, With a new Armours, Stainless Steel down pipe, And a standard length, Armours, S/S Silencer, Never been as quiet !, As I said before, I sawed a few inches off the tail pipe, On my other Silencer, I thought it made it more loud !. Cheers Bill.
Any performance hit compared to a straight thru pipe?
 

Bill Thomas

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VOC Member
It's still straight thru Martyn, But I played with the other silencer, To get it nearer 58", Which was the racing length, For 1. 5/8" pipes, It is now pulling 69 mph easy enough, I am trying to save the Engine, The bottom end has not been apart since I built it in 1977, And I am still thinking about the breakdown I had last year with my Special, Don't like Breakdowns !!. Cheers Bill.
 

Black Flash

Well Known and Active Forum User
VOC Member
Bill Thomas wrote that he thinks his bike is louder after sawing of part of his tailpipe,this woke up some memory.
I used to have a 500 matchless single with a "slash cut" tailpipe. You somehow loose the tuned length of the exhaust doing that, but as the majority of us use the bike on the road I think it's not a problem.
It does not make a big difference, but this little mod was noticeable. Sort of every little thing helps mod.
Rather than cutting off you tailpipe just temporaly try to fit a 45 degree cut extension pipe and check it out. Only 30 minutes in the shed and you will know.
By the way it is 30 minutes of personal freedom playing with your favourite toy

Cheers Bernd
 

Bill Thomas

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VOC Member
I think this is why we have these old bikes ?, You can Play for hours/ Years. Will we ever get it Right ?.
Cheers Bill.
 

Monkeypants

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Non-VOC Member
After removing the blue patch on the Spares Co. spiral baffle silencer for about the 20th time I tried messing around with an old silencer.
Someone suggested cutting the end cap off and removing the innards, then replacing with a fluted tube etc.
I have had luck Tig welding with 304 or 308 stainless rod on chromed silencers. Once the weld was polished things looked factory fresh.
This time I made the mistake of cutting the end cap right at the joint, which turned out to be a brazed connection.
Tig welding and brazing do not mix well!
Should have moved the cut in a quarter inch, then it would have welded up ok.
I don't know the supplier of this silencer but it also was of the spiral baffle type.
It was very restrictive though, much moreso than the Spares Co. item.
First I tried tacking the end back on with nothing inside the silencer. Sounded nice but loud on startup. Sounded godawful ( flat and loud) on dyno hill . Speed on the hill was exactly the same as with the Spares Co. spiral baffle silencer fitted, hit at 70 mph and hold at 70mph all the way to top.
I took it apart and tacked in a ventilated1 1/2' tube. This helped a bit with the sound but somehow I lost 2 mph on the hill.
I tried it several times and it pulled down rather than held each time.
And still sounded awful!
Now it was looking awful too.
So after reading this thread and Bill's recommendation, I ordered an Armours SS straight thru silencer.
It arrived yesterday. It looks well made and fitted nicely. There is no clamp ring needed, that is built into the pipe, which is a neat solution.
Sound is quite loud but mellow, I like it.
Power on the hill was the best yet.
It was very satisfying to see the 5" Chronometric click up to 72 mph halfway up the hill then hold that to the top.
I did 4 runs, at which point it is time to leave ( speed limit is 35 mph)
Everytime the speedo clicked up from 70 to 72 and held.
Price was very reasonable too, just over $200 CDN shipped. I believe the Spares Co silencers are about $4-500 CDN.
I don't expect it will ever go blue, there is just no restriction. It will go that very pleasing straw gold colour, that's already started to occur.
It's also a fairly light silencer.

Thanks Bill
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Thanks Glen, Not sure what part of the throttle you are on, But get some more petrol in there, And go for 75 !! :) . I think it will go quicker, If you take a bit off the tail pipe, I did it, But now wish I had not,
Don't look right, Maybe it will cost me another silencer ??.
I must leave things alone !.
Mine haven't gone too straw, Because it's a long way from the hot bit, But I put a SS down pipe on the Comet,
And it went straw in seconds, But it's nicely polished , So doesn't look too bad to me.
Cheers Bill.
 
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