Marble mod slowing bike down

[jermzfree]

I have an 03 stock that backfires on decel around 4k. Tried the marble mod as a bandaid solution and TA DA!! no backfire, pops or farts on decel. Only now the bike is noticabely slower

I don't know enough about that tube going from the airbox to exhaust to know if that makes any sense or not. Any ideas??? I read all the threads on stock backfireing and really want to fix the cause of the problem. This is what I had in mind of trying in order:

1. replace plugs with hotter type
2. check valve tappet clearance
3. take it to a dyno and see what they think.

Anything else I should try?

 

[Mr Bogus]

Unless this bike uses an O2 sensor to control mixture, then you are imagining this "slow down"

The PAIR valve is the Hayabusa equivalent to the AIR (Air injection reactor) system on cars... it just pumps some fresh air into the exhaust pipe to help consume excess hydrocarbons before they go out the tail pipe... ZERO effect on power...

the back fire is because the control system has failed and is not shutting off the air under deceleration..

 

[rockadaous]

back firing with stock exhaust.

 

[TA_GunSurgeon]

Unless this bike uses an O2 sensor to control mixture, then you are imagining this "slow down"

The PAIR valve is the Hayabusa equivalent to the AIR (Air injection reactor) system on cars... it just pumps some fresh air into the exhaust pipe to help consume excess hydrocarbons before they go out the tail pipe... ZERO effect on power...

the back fire is because the control system has failed and is not shutting off the air under deceleration..

Out of curiosity why would it slow it down if it had a 02 sensor?

 

[jermzfree]

the back fire is because the control system has failed and is not shutting off the air under deceleration..

Can you talk a little more about this "control system". Is it part of the pair valve?

 

[Mr Bogus]

Unless this bike uses an O2 sensor to control mixture, then you are imagining this "slow down"

The PAIR valve is the Hayabusa equivalent to the AIR (Air injection reactor) system on cars... it just pumps some fresh air into the exhaust pipe to help consume excess hydrocarbons before they go out the tail pipe... ZERO effect on power...

the back fire is because the control system has failed and is not shutting off the air under deceleration..

Out of curiosity why would it slow it down if it had a 02 sensor?

The 02 sensor feedback would be calibrated for the air injection.. a failure of the AIR system will skew what the sensor sees, the amount of skew would be dependent on how much weight the ECU puts on the sensor value..

 

[Mr Bogus]

the back fire is because the control system has failed and is not shutting off the air under deceleration..

Can you talk a little more about this "control system". Is it part of the pair valve?

if you look at the front of the motor, you will see the "box assembly" with the small vacuum hose and the large air hose from air filter box attached, there are also the 4 lines out to the head where the block off plates go.

The small vacuum hose is the "control" hose
The large hose is the "source air" for the system
Finally you have the 4 lines that go to where the block off plates are installed..

The design is a "passive" type that does not require a pump.. The ports are designed to create a vacuum at the port and so it "sucks" in fresh air when the line is "open"

The control valve must close during deceleration or you end up with the backfire.. by stuffing the marble in the system, you are basically closing the valve and so no more backfire.

 

[jermzfree]

I purchased my Hayabusa last winter and have only ridden it in very cold weather. Yesterday when I rode the busa it was warm out and I bet it seemed a little slower because of that.

I have one more question about the pair valve. What prevents the control system from operating properly? Not enough back pressure in the exhaust? Should I be worried that my stock bike is needing the marble mod to operate properly?

Thanks for the good input

 

[OZZY]

the marble mod will not make ur bike slower. that is a total imagination thing for sure! witha stock exhaust, you shouldnt be needing the marble mod...

 

[javie]

I purchased my Hayabusa last winter and have only ridden it in very cold weather. Yesterday when I rode the busa it was warm out and I bet it seemed a little slower because of that.

Colder air holds more oxygen so you can stuff more air into your engine and make more hp. I noticed on my neon a long time ago that during winter it seemed a lot faster than in summer