After cleaning my dual carb setup (Stripped everything, cleaned with carb cleaner, blew out all the valves, etc.), my 1983 RX7 is having some issues getting back to an 800 rpm idle. Before I did this, the car idled great at 800 rpm.

Here is what I have done:

• Replaced needle on both carbs (I tested the car with the old needle as well as the new needle, no change)
• Replaced all copper washers
• Cleaned carb
• Cleaned all jets
• Replaced gaskets
• Adjusted floats
• Made sure the fuel pressure was ~3.5 PSI
• Reset the mixture and idle screw to stock

Here are my symptoms:

• Finger over the choke air inlet of the rear carb makes the idle go smooth. Finger over the choke air inlet of the front carb makes the car idle so low it will stall.
• Backing out the idle jet on the rear carb a half turn makes the idle go smooth
• Rear carb does not drip fuel from the main jet while idling (not sure if this is the correct name for it, but it is the jet that sits in the middle of the venturi). The front carb drips fuel continuously. I attached a video of what I am talking about.
• Cant get the car to go below 1500 rpm while adjusting the idle mixture screws
• Idle mixture screw of the rear carb does not affect the idle

Circled is the "main jet" that drips fuel continuously in the front carb and doesn't drip at all in the rear.

 

Sounds like multiple things going on.

I wouldn't expect enough signal to be high enough to draw fuel from the main - I'd validate float level on the front. If the idle screw on the rear is doing nothing I'd think the idle circuit or jet is clogged.

 

It sounds like a vacuum leak. Make sure your hoses aren't cracked or leaking. Spray some starter fluid around the base and other areas you might have a leak to see if the idle speeds up. If it does, you've found your leak. You may have other issues as well which makes it a pain to trace down.

 

Accidentally posted twice.

 

I’ve been working on the carbs for the last few days. Followed everyone’s advice and checked float levels as well as checked for vacuum leaks.

No leaks and the float is fine.

I’ve switched the entire head of both carbs around and the issue is still present in the front carb, so it’s not float level. Started switching jets around and that still didn’t do anything.

Today I found a way to stop the fuel from dripping from the main jet (I now know it’s called the discharge nozzle)

If the choke is on and the hole circled below is covered with my finger, the fuel stops dripping. The hole being covered when the choke is off does nothing. Any ideas?

 

Hunt down O'Skool on this forum (or something similar) -- has a lot of experience with this setup.

 

@rwatson5651 and @msimonov both have these setups and may be able to steer you in the right direction. What you think guys?

 

BTW -- slightly off-topic: I'm a big fan of the divorced choke used on the 36DCDs. I'm old enough to have owned many carbureted cars -- Mazda, Toyota, Jeep, Ford, Chevy -- and the divorced choke seems to do a better job than any of the butterfly setups. As a bonus, you can hear it, so there's confirmation that it's working.