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Discussion Starter #1
Rode my 950sm without earplugs for first time yesterday and noticed a burbling (don't know how else to describe it) when rolling off the throttle, especially when warmed up. Not quite a popping but almost.

I'm running standard cans but the previous owner had aftermarket jobs. Could he have had the needles lifted and because it has standard cans the fuelling isn't right or is the noise normal?
 

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Discussion Starter #3
So when fitting after Market cans is the needle adjustment to run leaner or richer?
 

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Discussion Starter #5
That's what I thought. Was hoping to bung the fuel cans on without carb fettling in short term
 

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It's a common misconception that this is caused by running rich. Violent backfires in the exhaust do indicate grossly rich fuelling (or other possible problems with the engine like poor timing) but burble/popping is normal. That said burbling can become excessive because of air leaks in the exhaust, which you might want to check as you've swapped end cans around. Burbling/popping does not indicate fuelling problems and similarly the presence of popping does not indicate the fuelling is correct.

Bill
 

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My 950 SMR did this from new with standard cans and still does it with the Leo Vinces on.

Not worried about it one bit ,in fact thing it sounds pretty cool to me!!
 

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I love the burbling on the overrun and sadly even try to make sure it happens when riding through towns :rolleyes:.

My old Triumph had a sports can that wasn't exactly subtle but just bearable (but illegal) but whoever put the Scottoiler on it didn't connect it properly and air was getting into the system (I didn't know this at the time).
It started popping a bit and over a couple of rides it started getting worse and was creating rather loud backfires. It all came to a head outside Lewes County Court building, where there are some traffic lights and it is a narrow street with plenty of echo. As I came up the lights I could feel the system building up for a big burp and tried to control it but the inevitable explosion sounded horrendous - trouble was there were about 6 coppers standing outside and the look on their faces fortunately was amusement rather than 'were going to get you'.
I was straight down to the bike shop on the way home to get it fixed :redface:.
 

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... That said burbling can become excessive because of air leaks in the exhaust, which you might want to check as you've swapped end cans around...
Hi Bill,

where/what would you check / how would you assert this on a Duke, please?

Ta.
 

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Hi Bill,

where/what would you check / how would you assert this on a Duke, please?

Ta.
My Duke 2 used to pop and bang a bit exessibly and sealing any point where 2 pipes met with either high temperature silicone or exhaust putty has fixed the bangs. It still makes the popping and burbling noise which I like but the BANGS have ceased. Sounds much better and runs smoother. :D
 

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Discussion Starter #12
Seems to be getting worse and running a bit lumpy atblow revs unless it's my imagination
 

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You know there's a gasket in the exhaust system on the 950s, at the first joint on the pipe coming out of the rear cylinder, low down, that needs to be replaced every major service I think. In my experience they start to fail after 18 months or less. As it starts to go you get louder and more exhaust noise.
Just changed mine, and it sounds like a new bike.
 

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following on from what bllx said, my gasket (base of rear cylinder exhaust) blows every 1k miles or so, and you can hear it starting to go after as little as 250 miles. also the big round connector at the base of the Y piece needs packing with exhaust sealant every 2k miles ish (on my bike anyway)

it's bloody annoying as it makes the bike very vibey when they are both fully gone! easily fixed, however :)

that said, the gasket lasts much longer with baffles in (apparently ;))
 

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more this - yesterday i replaced the graphite gasket (£8 from a KTM dealer) and had to re-seal the Y piece (which is a terribly designed piece of exhaust - it doesn't fit together well and the big circular clamp doesn't do a very good job either)

the gasket lasted 1800 miles (there was still a little bit left) and the under side of the Y piece's heat shield was covered in soot from where exhaust joint was leaking due to its crap design.

it's all now nicely sealed again - the bike is smooth, doesn't pop and bang (yet ;)), and doesn't hesitate at low revs. it's like a new bike!

takes about an hour to do btw

:smokin:
 
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