Quote: However, cutting a spring is quite err... definite. Could be hard to find a new one if needed.
Hi, After spending 3 weeks messing with carbs and mainly the Air Cut Off Valve I feel somewhat enlightened on it.
This is ONLY my opinion and I dont mean to tread on peoples toes but:::: cutting the spring is NOT the way to go.
The design on the air valve is rather clever... should you take it apart you will see at the rear of the diaphragm is a small piston shaped rod, under normal running, tickover, cruising and accelerating the spring holds the piston to the back of a recess allowing unrestricted air into the carbs via a small drilling.
Once the throttle is closed there is a vacum in the air valve and the small piston is sucked towards the outside of the recess closing the 2 air holes making the mixture richer.
If you were to cut that spring lessening the tension the vacum would actually pull the piston out covering the holes at idle and richen the mixture considerably, on over run (high vacum) the piston would be pulled PAST the holes so defeating the object. The spring is a designed length to allow the movement to work but it also acts as a stopper when fully compressed to stop the piston moving out the opening too far.
To disable the valve is a simple matter of undoing the 2 screws and place a small bit of a plastic bag OVER the O ring to stop the vacum. Cheap and reversable.
Hope that might help someone.. I spent ages playing with it, springs, tape, vacum gauges so I have a very good understanding of how it works.
