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exhaust modification

F

fubarguzzi

Just got it firing!
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I have a 71 Ambassador I am using Davidson Sporster stock mufflers the noise is absolutely unbearable,so I welded a washer into the exhaust pipe Just in front of the muffler. Heres the problem the pipe is 1and a quarter inches diameter my restricted opening is three forths is that not enough opening or how do I know when the restriction is big enough ?
 
What John said.

Reducing noise by simply restricting flow is not a good way to go about it. A good muffler has a lot of science in it in terms of achieving maximum flow, allowing shock wave tuning as well as the obvious.

The original Ambo mufflers also actually look nice.
 
And if you were going to do something as cheesy as welding a washer in there to reduce the flow and thus the noise, weld it in at the back of the muffler not the front of the muffler. You would want to restrict the flow coming out of the muffler, not restrict the flow going in to the muffler. A reducer/restricter at the exit of the muffler is a common bodge to quiet down a too loud muffler. But putting H-D Sportster muffler on a Guzzi....... H-D mufflers are horribly inefficient and would be a terrible choice, other than that they must be cheap and readily available because few people actually use them...... Because they don't work well.
 
Not everyone has $700 to spend on mufflers. The mufflers linked to have much smaller outlets than the originals (by nearly 15 mm) and are very quiet and rather restrictive as well. The closest to original US mufflers in both form and function are those available here, Code GU03, "America con foro grande":
http://www.motostoricheitaliane.com/EN/guzzi-1.html

There are much better budget friendly choices than Harley mufflers. I've installed the long Emgo megaphones and they work okay (approx. $120 a pair) and one of my current customer projects will be getting MAC "Whispertone" mufflers which are made specifically for the Loopframe Guzzis, sound very nice and are a reasonable $275.
 
I've fitted a set of replica Dunstall Megatrons on my Cali and these do seem to work acceptably well for what is essentially an inexpensive solution. They can be bought from Burton Bike Bits http://www.burtonbikebits.net/ over here in the UK but how pricey they'd be once shipped to the USA I don't know. From my experience the main thing with Guzzi pipes is to have mufflers that are long enough as they don't seem to like short pipes, I would aim for keeping the balance pipe under the gearbox and having pipes that reach as far as the rear wheel spindle and see how that goes.
 
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