I call it a built in backfire.
While my motor was out I deleted this.
The exhaust air injection takes place at the 2 black steel pipes attached below the exhaust header exits.2 off 6 mm studs with 10mm nuts. per cylinder
DaNGER, the front cylinder 6 mm flange mount studs get corroded , one of mine sheared, got it out with a nut welded on the stub.
Lube/ heat these studs well.
The steel pipes sneak around the cylinder and join rubber hoses which enter the PAIR v/v mounted on a bracket to the rear cylinder.
The air connection from comes in the top of the PAIR v/v via a hose from the air box.
The inlet manifold vac signal is taken from the rear pot inlet manifold.
Undo these connections,
That each exhaust small manifold, the air box pipe and the vav connection.
Unbolt the mount at the rear cylinder and remove the whole mutant octupus.
Now plugging the holes.
Air box, an 8 mm short allen bolt loctited in .
Vac manifold a small screw loctited in.
Exhaust tappings.
I sawed off the flange from the steel pipe and tapped the centre to take an 8 mm short allen bolt with a fibre washer, then refitted with gasket goo and original studs.
shows new blanking plateResult , no backfires on overrun, much tidier and 1 and a half pounds lighter.Tidier looking motor.
horn now lives where the valve didWarning , it is very difficult to reach the rear exhaust flange without engine removal dont even consider it.