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Discussion Starter #1
Anyone else experiencing a lot of popping from the exhaust when coming to a stop from 1st on down? Usually happens when I am completely off the throttle. I don't remember it being as pronounced in the first 300-400kms.

I am due for the 1000km service tomorrow, and I'll make sure to mention it to the mechanic. But anyone else experiencing the same thing?
 

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My streetfighter does this if it's warm. It has the termi slip on exhaust, but it seems to be normal and definitely did become more pronounced over time.
 

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Yep but I love it, glorious sound :D

This is my understanding - closing the throttle tells the fueling to move to a lean state, if you are decelerating at the time the momentum of the bike is actually driving the engine at a speed greater than the closed throttle fuel mapping can keep up with.

Lower back pressure in high flow aftermarket exhausts lean out the mixture even more.

I ran my low race termi for a couple of weeks without the up-map and the popping was quite excessive. The new map has definitely helped - I now only get a few pleasing pops :)
 

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Discussion Starter #6
I love the sound too, just wondering if it's a sign of something bad. Like running too lean or something.


Boom. You're it!
 

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From Mikuni American

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.
Why This (normally) Happens:
1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
5) The exhaust must be both free-flowing and have an open exit for the popping to occur.
 

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I agree with everybody that:

1. It does pop and burble on deceleration
2. It's normal and okay that it does this
3. It sounds fantastic and makes me smile :)
 

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Discussion Starter #12
Mechanic at the dealer said its perfectly fine as well, good to know… He also said that its more noticeable on hot days.
 

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Applying the tiniest bit of throttle, like just "pressure" and not actual twist, when slowing down will give you lots of extra little pops and burbles, which I'd assume comes at the cost of slightly less fuel efficiency since you are injecting a little fuel. Not sure if it's a good or bad idea (probably not good), but I catch myself doing it every once and a while (because sometimes I'm a 13 year old inside).
 

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Applying the tiniest bit of throttle, like just "pressure" and not actual twist, when slowing down will give you lots of extra little pops and burbles, which I'd assume comes at the cost of slightly less fuel efficiency since you are injecting a little fuel. Not sure if it's a good or bad idea (probably not good), but I catch myself doing it every once and a while (because sometimes I'm a 13 year old inside).
Will do that under some railway bridges!!! Thanks I'm 10!
 
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