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Discussion Starter #1
2014 Nomad 1700.

Installed V&H slip-on pipes and a used Cobra FI2000 Powerpro I bought from a member here. Immediately after installation of the new pipes, had lots of backfiring during down-throttle. Installed PowerPro, it reduced, but didn't eliminate it.

PowerPro has a note in the installation instructions (which are excellent, BTW, so credit Cobra for that) that backfires during throttle-down are usually caused by air leaks due to improper exhaust system installation.

I could take it to the shop, but I'd rather figure it out on my own. I'm not much of a mechanic, but I'm trying to learn. Where should I start looking? I thought I got all the clamps on and properly tightened, but there were no torque specs with the V&H instructions, so I was hesitant to just keep cranking them down.
 

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Premium Member
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2014 Nomad 1700.

Installed V&H slip-on pipes and a used Cobra FI2000 Powerpro I bought from a member here. Immediately after installation of the new pipes, had lots of backfiring during down-throttle. Installed PowerPro, it reduced, but didn't eliminate it.

PowerPro has a note in the installation instructions (which are excellent, BTW, so credit Cobra for that) that backfires during throttle-down are usually caused by air leaks due to improper exhaust system installation.

I could take it to the shop, but I'd rather figure it out on my own. I'm not much of a mechanic, but I'm trying to learn. Where should I start looking? I thought I got all the clamps on and properly tightened, but there were no torque specs with the V&H instructions, so I was hesitant to just keep cranking them down.
Michael, Is it running any better. I would think You notice the difference in roll on Oomph! I bet You also had the popping through the exhaust before the V&H slip-ons, but, just could not hear it as well. On another note, My voyager never backfired loud with D&D pipes or with the current FPE true duals on it now. That power pro was on there right after I put on the D&Ds.
 

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We have all been threw this as mine did it to, but after plugging the AIS system that helped & then getting a better map for my PCV (Power Commander 5) it has been almost gone. I'm not familiar with your Powerpro can you install different maps or program it?
 

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My first question would be did you plug the tube leading to the pair valves, in the right side throttle body cover at about the 11 o'clock position...
 

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I plugged the tube, installed the throttle body gasket, switched to 87 octane fuel, and installed a K&N filter. Combined efforts significantly reduced, but have not eliminated backfiring. Running FP true duals with a Cobra PowerPro. As a note, installing the K&N increased the air in and really made a significant improvement as the engine isn't fighting for air like it was. I have been very pleased.
 

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BOTM Winner, May 2015
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740 Posts
if you twist the cable going into your power pro, the lid will come off, you may have a blue adjustment in there, for fuel adjustment, lean or rich
 

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Discussion Starter #7
Thanks for the input so far, guys. I have a new throttle body gasket and BAK on the way.

So it sounds like nobody thinks the problem is really improperly installed slip-ons?
 

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I had a lot of decel popping on my Hayabusa with a full racing pipe. I blocked the pair valve but that didn't help much. What I did was to tinker with the AFR in my power commander. First I dropped the fuel down to -15 on anything below 1000 rpm at 0% throttle. Then I tried adding fuel. I found on that bike (and every application is going to be different) that +8 on anything below 2000 rpm in the 0% throttle worked perfect. It was making the air fuel mix that was left over to unstable to burn, thus eliminating the decel pop. Only time I would still get it was when I would wind it out to 11 or 12k rpm and then let off.
 
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