It's difficult to install a slip-in incorrectly on a 400 so I would not be too concerned. The back fire is normal under certain conditions, my ZX6R back fires on decel after the ECU flash and slip-on was installed. Black soot is likely the result of altered AFR because of the slip-on flowing more efficiently. Do you have an aftermarket air filter or ECU flash?

 

It's difficult to install a slip-in incorrectly on a 400 so I would not be too concerned. The back fire is normal under certain conditions, my ZX6R back fires on decel after the ECU flash and slip-on was installed. Black shoot is likely the result of altered AFR because of the slip-on flowing more efficiently. Do you have an aftermarket air filter or ECU flash?

yeah, ecu flashed by vcyclenut

 

i have responded to your email, the flash was for the stock bike so you pair valve is still active which is what is causing the popping

the reflash is free , you just have to pay for return shipping and ill update the flash for the slip on which is a few changes over the stock pipe flash

here is why the pair valve causes popping on decel, its not an indication something is worng. It was popping on decel before you installed the slip on , you just could not hear it

 

i have responded to your email, the flash was for the stock bike so you pair valve is still active which is what is causing the popping

the reflash is free , you just have to pay for return shipping and ill update the flash for the slip on which is a few changes over the stock pipe flash

here is why the pair valve causes popping on decel, its not an indication something is worng. It was popping on decel before you installed the slip on , you just could not hear it

thx! I was thinking the bike bike gonna explode after a long ride lol.

 

For reference, I never install block off plates when I get an ECU flash because I leave the cat in place. The popping on decel isn't super obnoxious to be a nuiseance IMO, but everyone has there own opinion on what is acceptable.

The ZX6R has a decel fuel cuttoff that when disabled keeps the injector ON which in turn causes extra unburnt fuel, increased back fire/popping on decel. Now sure if the ZX-4RR has a decel fuel cuttoff but that is going to increase backfire as well if disabled.