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.
View attachment 290877
Access is hindered in my case with the after-market horn.
View attachment 290878
Disconnected and removed the horn and found it was secured with the missing engine casing bolt
@n_g_rjun
View attachment 290879
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.
View attachment 290880
Disconnect all of them and remove the 10-mm bolt.
View attachment 290881
And it will come off.
View attachment 290884
View attachment 290882
View attachment 290883
View attachment 290885
View attachment 290886
View attachment 290887
Four screws hold them to the clamp as well as secures the cover. Removing them opens up the AIS as well.
View attachment 290890
View attachment 290888
Base part where exhaust port connects. Coal-like debris.
View attachment 290891
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,
View attachment 290892
but on the other side I see an O-ring and a retainer washer. Something is not right.
View attachment 290893
It was oily all over.
View attachment 290894
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.
View attachment 290895
Opened the intake manifold-fed side. It's spring-loaded and negative pressure/suction force from intake manifold pulls the diaphragm outwards.
View attachment 290896
View attachment 290897
The shaft on the other end is where the fallen valve belongs.
View attachment 290898
Found the location of the o-ring.
View attachment 290899
Installed back the valve and secured with the retainer washer.
View attachment 290900
Normal/open position. Free flow of air to exhaust port.
View attachment 290901
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.
View attachment 290902
Cleaning up. Reed can be disassembled by removing the bolt.
View attachment 290903
View attachment 290904
Base and rubber lining can be separated and cleaned conveniently.
View attachment 290905
All cleaned and ready to install.
View attachment 290907
Reed assembled.
View attachment 290908
Cleaning the muck on the base.
View attachment 290909
View attachment 290910
Sprayed some throttle-body cleaner and wiped off. Effortless and effective.
View attachment 290911
Work in progress.
View attachment 290912
Spring on the diaphragm side.
View attachment 290916
Assembled and ready to install.
View attachment 290915
Rubber piping to exhaust port. Cleaned that with diesel and some TB cleaner.
View attachment 290914
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.
View attachment 290913
Installed and all tubes connected.
View attachment 290917
This is where the tube connects to the intake manifold.
View attachment 290924
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.
View attachment 290925
New flange bolt for horn/tank mounting.
View attachment 290918
Thread gone in one of the tank cover nut springs.
View attachment 290919
The ₹80 Yamaha part I have been saving for years. Heard new ones are cheaper.
View attachment 290920
Pulsar fairing bolts. Cheap and of good quality.
View attachment 290921
Checked air filter box for oil and there was just a trace.
View attachment 290922
All set and done.
View attachment 290923