10-18-2017, 12:57 AM
What is the purpose of removing the HS needle?? That makes no sense to me, and I've never seen anyone do that.
I followed the first link and read EC Birt's write-up, and I saw that he mentioned the purpose was to avoid "blowing up a balloon." Um, I still don't get it.
Some of his other commentary seems to cloud the issue a bit, IMHO. The whole point is, the force countering the "pop-off" spring is venturi vacuum working on the wet side of the metering diaphragm. With a venturi that's on the small side, there will be plenty of vacuum to pull the diaphragm in, and that little spring will be no match for it. The only reason anyone ever has to monkey with the pop-off spring is when they're running large/multiple carbs, making the venturi vacuum much less.
BTW, in order to get a crisp pop-off reading, I've always had to slather the needle area with WD-40 and then jiggle the needle around in it before EACH measurement. In the video, he mentioned that, but didn't seem to have to do it all the time.
The thumb-pump in my pop-off gauge never sealed right from day one (bought new). Highly annoying, although it has helped to build the muscles in my opposable thumbs... my near ancestors would be jealous.
I followed the first link and read EC Birt's write-up, and I saw that he mentioned the purpose was to avoid "blowing up a balloon." Um, I still don't get it.
Some of his other commentary seems to cloud the issue a bit, IMHO. The whole point is, the force countering the "pop-off" spring is venturi vacuum working on the wet side of the metering diaphragm. With a venturi that's on the small side, there will be plenty of vacuum to pull the diaphragm in, and that little spring will be no match for it. The only reason anyone ever has to monkey with the pop-off spring is when they're running large/multiple carbs, making the venturi vacuum much less.
BTW, in order to get a crisp pop-off reading, I've always had to slather the needle area with WD-40 and then jiggle the needle around in it before EACH measurement. In the video, he mentioned that, but didn't seem to have to do it all the time.
The thumb-pump in my pop-off gauge never sealed right from day one (bought new). Highly annoying, although it has helped to build the muscles in my opposable thumbs... my near ancestors would be jealous.