G'Day Mate, yep, that's my old K1, "Battle Scarred Galactica". The air filter system comes from one of the members here, Brian. (Tintop) It's the "Anti Pod" system that he designed, combining the benefits of velocity stacks combined with a freer flowing oiled foam filter.
The engine in my bike is "worked" with high comp 836cc pistons, Mike Rieck stage 3 head (bigger valves, ports opened up and flowed, etc) and Megacycle 125/75 race cam. I was having trouble tuning my 29mm CR race carbs so I re-installed a set of OEM Keihin carbs and played around with the stock airbox with OEM filter, a K&N filter, and pods. Although with the stock airbox with K&N filter the engine ran beter, I still wasn't totally happy with it so I installed Brian's filter setup with some 130 main jets and it runs real well now. I'm not sure if it's altered my torque curve etc, but the throttle response immediately felt crisper, with smoother, faster accelleration than it had before with the OEM airbox or pods.
I've just bought a set of 31mm CR's and several sets of needles and main jets to install on this engine as the stock carbs obviously don't flow as well as the CR's on a highly modified engine, particularly at higher RPM's when the 125/75 cam is coming into it's own, but for a stock or mildly tuned engine where CR's aren't necessary this setup is superb. Don't take that to mean that the "Anti-pod" setup wouldn't work well on CR's either, it's just that Brian hasn't developed a filter setup for CR's yet. If he ever does, I'll be ordering a kit right away. Cheers, Terry.