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What causes the secondaries to open

R

rmm

Regular Contributor
"Curious what causes the secon

"Curious what causes the secondaries to open? I know about when they open b/c can here it, but what causes this? I had initially thought it was a "preset" based on engine rpm.

Thanks"
 
"on the factory installed q-je

"on the factory installed q-jets, the secondary throttle valves are opened purely by the throttle position. They start delivering fuel when the air valve opens. This is controlled by the spring around its shaft and by the same vacuum break that functions as the choke pull-off. Its when the airvalve opens that you 'hear 'em kick in'."
 
The spring on the air valve is

The spring on the air valve is adjustable. It is set with a small set screw on the bottom of the air valve shaft and a wind up screw on the end of the air valve shaft. Typical stock setting is one to one and a half turns preload. I had my Q-jet set at 2 and half turns to make sure it stayed closed at cruise speed.
 
"I'd say the typical setti

"I'd say the typical setting is more like 1/2 to 3/4 of a turn, from the zero tension point. I've never wound one beyond a full turn. Everything I've read indicates going beyond that will distort the spring. If you want to keep the secondaries closed, you are better off just using safety wire - it pretty bullet-proof and also easy to undo, if you change your mind.

with my install, we found the secondary accelerator wells were dribbling while cruising. the permanent fix was a float adjustment and a rework of the throttle plate to delay the secondaries opening by about 8 degrees."
 
So with the motor not running

So with the motor not running can I advance the throttle and see them open?
 
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