[pete]

sound like the motor is pinking...
closing off the exhaust in to the inlet
there is now more space for air "O2"
to be sucked in so now the motor
is running leaner...

dumb ass idea...
you wouldn't run to well if yer had to eat yer own crap
so why would a motor...

SO.......
Are you sure its not a "AIS" (Air Injection System) , which makes a lot
more sence that exhaust gases going back into the motor.
My Yamaha XT660R has one... it lets air into the exhaust
to burn unburnt fuel that enters the pipe... clean air / low
exhaust exmissions etc...
Dose the motor pop/bang on a trailing/closed throttle out the exhaust pipe
as the unburnt fuel in the pipe is burnt..
on the XT closeing it off gives no more power...



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