Carbs
Thanks PK for the very thorough but understandable theory (and practice) of PJ function.
I may very well have some misconceptions 'onboard':
The main one relevant to this being that if the MJ affects the function of the needle atomiser (shall we say from 1/3 to 2/3 throttle because of the overlap) then it is fundamentally too big or too small for the set-up.
The other was (is) that the PJ immediately shut down at 3/4 throttle. Thinking about it, even with the slide closed behind it the vacume is still sufficient to deliver a/f mix that will be drawn under the slide. You are saying that the jet is also flexibly progressive in it's delivery: given it's size and location this fact is a unexpected revelation to me.
Still puzzled why the dynoed S4 too hundred had regular (approx 2 second intervals) over fueling at WOT on the stand. It performed well on the road with no probs under heavy load and thrashing.
I don't think any of my larger cc piston-ported with big inlet duration would respond as well as u describe to the throttle being 'snapped' from tick-over to WOT. Rolled on over a second yes, but not snapped. Perhaps a factor of carb size, inlet timing, and 'conservative' jetting?
V. happy with Keihin performance improvements overall, though I find em more sensitive to altitude and air pressure/weather than lesser makes. Might grab a PJ one one day, or stick the Dellorto adjustable in one.
Cheese for the input geez!
I may very well have some misconceptions 'onboard':
The main one relevant to this being that if the MJ affects the function of the needle atomiser (shall we say from 1/3 to 2/3 throttle because of the overlap) then it is fundamentally too big or too small for the set-up.
The other was (is) that the PJ immediately shut down at 3/4 throttle. Thinking about it, even with the slide closed behind it the vacume is still sufficient to deliver a/f mix that will be drawn under the slide. You are saying that the jet is also flexibly progressive in it's delivery: given it's size and location this fact is a unexpected revelation to me.
Still puzzled why the dynoed S4 too hundred had regular (approx 2 second intervals) over fueling at WOT on the stand. It performed well on the road with no probs under heavy load and thrashing.
I don't think any of my larger cc piston-ported with big inlet duration would respond as well as u describe to the throttle being 'snapped' from tick-over to WOT. Rolled on over a second yes, but not snapped. Perhaps a factor of carb size, inlet timing, and 'conservative' jetting?
V. happy with Keihin performance improvements overall, though I find em more sensitive to altitude and air pressure/weather than lesser makes. Might grab a PJ one one day, or stick the Dellorto adjustable in one.
Cheese for the input geez!
The adjustable ones are more useful in my opinion as you can adjust/cut the length of the tube that protrudes into the venturi, therefore have more control over when you want it to start delivering and of course you can adjust the top srew to let more or less fuel through 
I have to say that they are not the easiest things to set up though but they are worth while.
I have to say that they are not the easiest things to set up though but they are worth while.