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E: Engine Exhaust butterfly valve?

Howard

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VOC Member
To prevent boredom during lockdown, I've been doing jobs on the Comet that needed doing and some that didn't need doing, including fitting some bits I removed from the Egli when I detuned it, including Mk2 cams, which we all know won't work right with a silencer. Unfortunately, the straight through silencer I fitted is a tad on the loud side.
Before I start reinventing the wheel, has anyone fitted a butterfly valve to deaden the exhaust note - it might come in handy when passing horses in Peak District lanes.
The previous exhaust was pretty loud, and the bike backfired when shutdown, which left me with 2 wrong choices when I saw animals on or near the road.

H
 

erik

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backfire or detonation is when there is an air leak in the exhaust system.I would check the connection in the cylinder head first.Erik
 

vibrac

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I did this many years ago
no mater how I arranged it the gas flow would open it or sometimes even close it at the most inopertune moments. It would work the cable and the choke lever I employed unless it was too tight to move.

A rotating barrel with matching holes would be a way to try
when I had a AJS 7R on the road (What a great year that was!) I would stick a foot over the exhaust pipe end if I wanted a bit of quiet (just as I was coming home late with my push bike lights) a long stretch but I was young but the boot got hot!
 

Vincent Brake

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Yep for sure it works.

On a gilera 500 saturno sport its called a "horse valve"
That is in Dutch...
 

Oldhaven

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In my youth they were called Snuff or Nots, and were made by Pacifico. My best friend from high school and college used them on his open piped Honda 305 scrambler that I would borrow to see my girl friend in the next town. I think you would need the S-50 size, but they are nearly as vintage as me and our Vincents. They are not remotely controlled though.

2A5F3631-8EE2-4B16-9F0A-1B350C441CD5.jpeg
 
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Oldhaven

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VOC Member
I just found a parts diagram. The clever cupped washer and spring was what kept it in position at 90 degrees. Perhaps this can be used remotely if you want to make your own.

B048B647-28ED-4B14-BC0D-1784ED4B7C81.jpeg
 

Bill Thomas

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I don't think there is any point, My BMW K100 made no noise, Only a whine, And it still spooked them.
 

Howard

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It looks like the butterfly effect does some sound reduction, so it's out to the workshop (I wasn't doing much anyway) and I'll let you know what happens.
Thanks
Howard
 

Little Honda

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Try a longitudinal slot in the tail pipe of yr silencer, 4in x 3/8in, pointing vertically downwards. It does sweeten
the crisp note of yr straight through exhaust.
 

Howard

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Try a longitudinal slot in the tail pipe of yr silencer, 4in x 3/8in, pointing vertically downwards. It does sweeten
the crisp note of yr straight through exhaust.
Interesting, just got to work out how to do it with the kit available.
 

Howard

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VOC Member
I went to the filling station this afternoon for the first outing, about 3 miles round trip. The nipple pulled off the clutch cable as I pulled into the filling station!!!! Annoyingly, it's one of the few parts I haven't messed with in the last 2 months. I'd forgotten how much "fun" it was, riding without a clutch.
 

vibrac

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When the nipple pulled out of my throttle cable on my Bantam (years ago) I stuck the end under the petrol cap slipped my knee under the cable and worked the throttle with my knee luckily the bantam would not go over 50 or the wind could have caused a vicious feed back loop...
 

TouringComet

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The end of my clutch cable came off during the '99 International. We were at a motorway service station, wondering what the heck we were going to do. Then I spotted an AA table, to recruit new members. I asked them if they had a reciprocal deal with the AAA in the states. They said sure. We called for a truck, and unlike in the US, their trucks actually carry cable fittings. Back on the road, at no cost. What a deal.
 

roy the mechanic

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VOC Member
Before wrecking the silencer, I would be inclined to experiment on a plain extension pipe. The grass track sidecar guys put four slots in. They didn't remove the piece between the slots, they drove it inwards so it was visible from the end view. It won't make it much quieter but will take the"crack" out of it.
 

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