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While downshifting, is it normal to have the exhaust pop? It does it a couple of times, depends on how high the rpms are when I dump the clutch.

I can't really see what goes on behind me.

I hope at least it wakes up the cagers.

Thanks
 

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I have popping aswell..
It shouldn´t hurt anthing aslong as it´s only a "soft" backfire/rumble from excessive air and hot gas.. I think.

Is it to lean or to rich that makes it pop? I seem to recall that if it´s too lean, you can have poping.. I´m not really sure.. Mine got a little worse after the PC3 install (both leaner and richer in diffrent rpm´s @ 0 throttle)

//amullo
 

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Discussion Starter #3
amullo said:
I have popping aswell..
It shouldn´t hurt anthing aslong as it´s only a "soft" backfire/rumble from excessive air and hot gas.. I think.

Is it to lean or to rich that makes it pop? I seem to recall that if it´s too lean, you can have poping.. I´m not really sure.. Mine got a little worse after the PC3 install (both leaner and richer in diffrent rpm´s @ 0 throttle)

//amullo
I think the last time I posted about my exhaust, I determined I was running rich (plugs were not white) but the plugs weren't wet either. Who knows, maybe the bike is where it should be. Very hard for me to tell unless I take it down to the dealer...but it is a soft backfire/rumble.

Thanks amullo.
 

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it can also be a small leak in the joins of an exhaust system. look for a bit of soot at your pipe joints.
 

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I'm pretty sure it pop's like that if it's too lean. From what I've been taught by my guys. My dealer told me after I put my exhaust on, if it was poping and carrying on to bring it right in. The reason I would think it would have to be really lean is after my PCIII, my A/F ratio is up around 13:1 and no poping at all. Mine has never done it.

Funny story kinda related...last year at La Honda (La Ducati Day) they had a sound/loud muffler contest. A wide variety of about 10 bikes or so entered with every exhaust you can imagine. EVERY single one of them poped and cracked and carried on except for one beautiful 851 that didn't win but dang sure should have!!!. It was the crowd favorite hands down but the test equipment said otherwise. I think the test equipment was based on pure volume (db's) which should not have been the case. Anyways, I couldn't believe it. The bike that won was a new 999s with full Termi, but even that guy was poping and cracking. The guy that tuned my bike (Nick @ Munroe Motors) was there and I asked him why my bike doesn't do that??? He just laughed!! I wished after the fact I had entered because I think I could have won it...or at least mine wouldn't have been carrying on like that.
 

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I had backfiring all the time when downshifting, like when coming to a stop, when I was using the stock exhaust and chip. I think the dealer or someone mentioned this is actually a lean condition. I believe they intentionally make the bikes run lean to pass emissions. Once I got the half-system on there with the DP chip it didn't happen. BUt haven't ridden it enough to say for sure.
 

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grendels_arm said:
I had backfiring all the time when downshifting, like when coming to a stop, when I was using the stock exhaust and chip. I think the dealer or someone mentioned this is actually a lean condition. I believe they intentionally make the bikes run lean to pass emissions. Once I got the half-system on there with the DP chip it didn't happen. BUt haven't ridden it enough to say for sure.
I own a Honda VTX1800 also..... they are infamous for backfiring when decelerating..... This is the bikes way of burning off unused gas in the exhaust due to a pair valve on top of each cylinder. I don't live in CA so I really don't have to put up with any emission laws and have completely blocked off these valves on the 1800 and poof! no more backfiring. I am sure the Duc has some type of valve to help with this also. I would think it too could be blocked off with the correct fabrication. Shouldn't affect preformance either way besides some claim better preformance once the mod was done on the Big V-twin. Just my .02. :)
 

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It's my understanding this can be a either a rich or lean condition. I too have some slight popping upon decel. It seems to be from low to middle rpm's when shutting throttle. When in higher rev's on the track it isn't as prevalent. I don't think mines too far out of adjustment as the plugs are a nice light brown/tan color. I've never really worried about it as it doesn't seem to be a problem.
I have noticed the last couple of times at the AMA Superbike races at Mid Ohio and VIR most of the top runners were backfiring on deccel. Mat Miladin with the shorter can was very noticable. You can't hear it all too well on TV however at the track it's loud. Ken.
 

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My 749s pops like a mouth full of poprocks on decel. Remus pipes + PClll, tuner said the mixture is spec coming out the back,nothing to worry about. The pipes arent white,so its good to go.
It wakes up the nieghborhood deceling at 10,000 in first bwaahaaa!!!!!!!
 

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I'm no engine expert, but I believe most of the time backfiring is caused by excess gas igniting in the exhaust. My 748 does it a little bit, but I don't think anything of it. Especially if you are riding with a group of Harley guys, then our backfiring sounds like a melody. If the backfiring is loud, like a gun going off, then you need to get it fixed. You can actually harm your exhaust with that much backfiring.
 

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It's lean on over run. Normal, but irritating and embarrassing when it pops. Prevalent on a lot of bikes from many brands.

I'm sure you noticed the problem gets worse in hotter weather and when the bike is well heated up.

What happens is that when in deceleration, there is not enough fuel being passed by the injectors to allow it to burn well in the combustion chamber. It builds up in the exhaust system then POW, it lights off. No damage is done.

Check your throttle position sensor. I'm sure it's off therefore set too lean. 150 milivolts with the throttle plates closed. A Powercommander II as fitted to a 998 does nothing to the idle and low speed mixture. It starts working somewhere around 3000 rpm. (Don't know if a III will work on a 998)

Once I set the TPS (which was set at about 105) and get the bleed air screws set right, 99.8% of the deceleration popping was gone.
Your low speed and mid range power will also be noticably stronger.

The fix is free if you do it. Just takes some tinkering. Prolly would take a dealer 2 hours to set it up right.
 

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Please Please Please tell us how thats the only thing I couldnt figure out for my 6,000 and had to take it to the dealer. I have no way of knowing if they even did anything. I'm sure they did but you know how it is I'd rather do it myself.
 

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Scott R:

Thanks for the PM. Response here:
Unfortunately the 749-999 has a different TPS than the 748-998 bikes. I've seen it, it's smaller, but I have never tinkered with one.

With this in mind, I don't know the values to set it to. I'd trust the procedure is the same, but look in the shop manual for values and procedure. On the 748-998 it's dirt simple to set correctly. I recall someone mentioning linear vs non linear as the distinguishing differences between old and new. Don't recall if this is a factor for setup.

After I spent $650 for a 12,000 mile check and my bike ran like Sh*t, I got pissed off and went into it myself. Dealer had their Duc franchise yanked. TPS was never set although they stated set to 150 on the work order, valves were at or over the max settings, one belt loose the other like a guitar string, one cam off 2 teeth, and so on.
I read the manual and did it. These things aren't difficult to work on, and actually have a simple engine management system. If your skills are sorta advanced, have at it. Yet a sniffer would be a great tool for perfect tweaking.
 
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