Idling Issue

[Duckwing]

I have been chasing an idling issue for several weeks. I thought I had identified the cause - an intake manifold leak. The engine stumbled/died if carb cleaner was sprayed at the either intake port. I replaced the manifold gland/copper ring gaskets and cured the problem associated with the front port but not the rear. I have had the manifold off several times since but could never identify any problem. Today, I unbolted the hot air pipe then rotated it down to where it was lying on the hood former but still connected to the carb. I put a rag over the hot air pipe where it attached to the carb and retried the spray test. No engine idle impact at all. Repeated with my propane torch without issue. What appears to be happening is that the carb cleaner has been getting into the hot air pipe and sucked into the carb when I spayed the rear. I found an old forum post that warns that can happen. Guess I found it again.

So, now I am back to looking for the idle issue. I'm using a L4 carburetor.

[Steve Jelf]

Try an NH? Maybe somebody would lend you one until you find out if it helps.

[Duckwing]

I was using a NH and may have one somewhere. The L4 has been working for me. I noticed gasoline on top of the carburetor so something probably is amiss

[JRSpada4]

Has your L-4 been completely cleaned out? There are two small air passages that assist with idling and acceleration that should be clear. They are located down inside the carb where the mixture needle seats. One can be viewed through the the throttle side and the other through the choke side. They’re kind of difficult to get to.

http://www.mtfca.com/discus/messages/17 ... 1315688916

[Duckwing]

I probably need to open the carb and clean things out. Thanks for the tip on air passages.