June 2021 - AIS (Air Induction System) (Repairing and) Cleaning
AIS is one of the most ignored part in the bike (so did I), some end up bypassing it when it starts misfiring. It's a small diaphragmatic valve controlled by intake pressure differences and feed clean air to exhaust port to burn off unburned fuel especially at lower rpms and decelerating. Faulty one would end up acting like an EGR valve feeding exhaust gas into the air filter box and into the intake. Never cleaned in my bike, kept postponing, until a friend asked doubts about cleaning (which I had no clue of).
To start with, it can be accessed by removing the RH tank panel.
Access is hindered in my case with the after-market horn.
Disconnected and removed the horn and found it was secured with the missing engine casing bolt
@n_g_rjun
The AIS. Has 3 hoses, small one to intake manifold which controls the whole system. Other two goes to air filter box and exhaust port.
Disconnect all of them and remove the 10-mm bolt.
And it will come off.
Four screws hold them to the clamp as well as secures the cover. Removing them opens up the AIS as well.
Base part where exhaust port connects. Coal-like debris.
Reed valve set up on the top part. Partially blocked with debris as well. Clean these two and you are good to go in normal case,
but on the other side I see an O-ring and a retainer washer. Something is not right.
It was oily all over.
Popped open the side cover and found the air shut off valve fallen off. This might be the reason for untraced oil depletion and/or quick plug darkening, but the reed valve in between made that theory speculative.
Opened the intake manifold-fed side. It's spring-loaded and negative pressure/suction force from intake manifold pulls the diaphragm outwards.
The shaft on the other end is where the fallen valve belongs.
Found the location of the o-ring.
Installed back the valve and secured with the retainer washer.
Normal/open position. Free flow of air to exhaust port.
Shut off position, when activated. This blocks air flow. At higher rpm, suction force will be high at intake manifold, pulling the diaphragm in, shutting off this valve. Pressure will be high at exhaust port too, causing reverse flow into filter box, which is blocked by this valve.
Cleaning up. Reed can be disassembled by removing the bolt.
Base and rubber lining can be separated and cleaned conveniently.
All cleaned and ready to install.
Reed assembled.
Cleaning the muck on the base.
Sprayed some throttle-body cleaner and wiped off. Effortless and effective.
Work in progress.
Spring on the diaphragm side.
Assembled and ready to install.
Rubber piping to exhaust port. Cleaned that with diesel and some TB cleaner.
Exhaust port outlet. When disconnected, makes mild FFE/induction-like noise. Commonly seen blocked with bearing balls especially in commuter bikes and Unicorns even by ASC.
Installed and all tubes connected.
This is where the tube connects to the intake manifold.
and where it meets the air filter box. Other tube is for crankcase ventilation. It's been a long since stripped and cleaned the bike. Full of dirt.
New flange bolt for horn/tank mounting.
Thread gone in one of the tank cover nut springs.
The ₹80 Yamaha part I have been saving for years. Heard new ones are cheaper.
Pulsar fairing bolts. Cheap and of good quality.
Checked air filter box for oil and there was just a trace.
All set and done.