A pop-popping sound from my exhaust?

[CharliesAngel]

Picked up my bike from Desmoto this am. Changed out an ECU. and a little oil leak... took it to Burlingame for my meeting and heard a pop-popping sound each time I down-shifted, especially from 2nd to 1st gear and the clutch seems to be a bit loose...any ideas guys?

[remy]

It sounds to me like the fueling is wrong. There's too much gas and it's getting burned up in the exhaust.

We should wait to hear from the people who actually know what they're talking about, though. Is that right?

[DanTheMan]

I thought it was from being too lean.

Either way there is a air/fuel issue with the new ECU, may need to be tweaked a little. Or Exhaust system isn't put on correctly and there air leak.

Loose clutch?

you mean slipping under acceleration?

[mostrobelle]

It sounds to me like the fueling is wrong. There's too much gas and it's getting burned up in the exhaust.

We should wait to hear from the people who actually know what they're talking about, though. Is that right?

Hell no!  All of us armchair mechanics should chime in!   

I think both DATV and Desmoquattro had this same problem after a new ECU got put in.  I think it's just an adjustment.  The shop isn't able to ride the bike for 20 minutes on a mountain road to test out the settings.  They can only ride it around town when they test it.  I've had this sort of thing happen once in a while.  I don't think it's a big deal.   

[slowmotion]

(armchair mechanic speaking) I dealt with ecu issues for a while with my s4r. What I'd say :

What you're seeing is backfiring

- if your dealer did not mess with the pipes or the cans, chances are remapping the ECU induced a lean
or rich condition.
- if it happens on decel, chances are you running rich and remaining fuel is being burnt later in the pipes.
- try to characterize the problem and see if it happens at a certain RPM / throttle position. That's valuable data point to your mechanic.
- if you have a Power C., a good dyno-dude should be able to find out when it happens across the rpm range and adjust the ECU with more or less fuel.
- a throttle position sensor might help also along with dyno curves  so that the mechanic can correlate both
rpm and throttle position and adjust ECU accordingly.
- on my bike, I ended up fiddling with the air / fuel mixture adjustment screws. There's one per cylinder and they help regulate the amount of air that is being let in. Not recommended by the dealer (of course) but that was my last resort out of desperation and it actually worked. I adjusted either of them and found a position for the front cylinder screw that makes the ECU leaner and the backfiring go away.
The drawback is that it makes your ECU leaner across the whole range and supposedly lowers your power curve. To be honest, it's barely noticeable and with 116 rwhp on an S4r, I still have more than I need.

- also, with the pipes, if there is a leak, the dealer can either tighten them up or put some sealant.

No matter what way you go, this backfiring can be fixed or patched (or you can live with it).
G-luck and let us know what you found out. I'm sure there are bunch of folks out there with the same issues that remain silent.

-slowmotion-

[desmoquattro]

I'd take it back to Scott and explain what you're experiencing. The popping on deceleration may either be backfiring or pre-ignition. Both can be caused by a change in fueling, which is what probably happened when you changed the ECU. It may also be caused by valves that need adjusting, but I doubt that. You have the same pipes on your Supersport that I have on mine, but I rarely get backfire...only when the bike needs a tune-up.

When my S4R was popping on decel, I took it to Scott a few times. On the third try, they saw that there was a crack in my header pipe. They fixed it, and the bike's been good since.

[CharliesAngel]

Thanks to everyone for the feedback!! You guys rock! 
So I went on the Leo Vince Charity ride this morning and had a good opportunity to open up my bike a bit and got it real good and hot...that's what caused my starting problem 3 weeks ago after I got home from a loop around Tomales Bay.  Greyduc had to jumpstart my bike and we took it to Desmoto asap (Thank you!) 

We thought it was either the regulator or the alternator as I had just gotten a brand new battery end of last year (some of you may remember me missing the Napa ride  that took 2 weeks to organize with Hypurone  ).  They had the bike for one week and couldn't figure out what was going on as it would start each morning.  Then I went out of town and 2 weeks later, picked it up yesterday with a new ECU as it wasn't the first two things. 

Apparently, the popping / backfiring is a normal occurrence with newly replaced ECU's.  I noticed that it was doing it at 3-1/4 to 3-3/4 RPMs and that it felt like it was going to die when I would accelerate from a complete stop...

Scott thought it was the ECU as well.  But then something else happened that happened to me 3 weeks ago - they couldn't start the bike again when I got to the shop!  Apparently after a long stretch of riding when the bike got really hot, it would stop starting.  So, due to the whirring sound that it made when pushing the Starter, Scott thinks it's the "Starter" so they will put back my old ECU.  Verdict will come tomorrow...

Man this was a long-winded explanation... 

[remy]

But then something else happened that happened to me 3 weeks ago - they couldn't start the bike again when I got to the shop!  Apparently after a long stretch of riding when the bike got really hot, it would stop starting.  So, due to the whirring sound that it made when pushing the Starter, Scott thinks it's the "Starter" so they will put back my old ECU.  Verdict will come tomorrow...

I had an issue with an old VW Jetta where it would get hot from driving around, I'd turn it off to park, then it wouldn't start again until it got cool again. Turns out the wiring would heat up and because a shittier conductor of electricity and the full power from the battery wouldn't quite make it where I needed it. I wonder if you're for some reason having a conductivity issue with the heat.

[CharliesAngel]

I had an issue with an old VW Jetta where it would get hot from driving around, I'd turn it off to park, then it wouldn't start again until it got cool again. Turns out the wiring would heat up and because a shittier conductor of electricity and the full power from the battery wouldn't quite make it where I needed it. I wonder if you're for some reason having a conductivity issue with the heat.

Well...turns out it was my Starter.  One of the magnets had worn off in the cylinder and the brush was messed up (sorry, I'm not using the proper mechanical terms...they just look like round, flat'ish, magnetic-looking things... 

Desmoto rebuilt my Starter, took out the new ECU and put back my old one.  Picked it up this morning and it's running like new again... Yeah!! Thanks Scott/Jared/Mike/Darren!