I have a question on my N idle speed. It's a late 1950 side mount distributor - I have a new carb (marvel), new wiring, distributor cap, rotor, coil, plugs, wires, and even pertronix electronic ignition. My N will start fine, but I cant get it to idle below 800 RPM. I''m following the new carb settings procedures to dial in my new carb from myfordtractors.com, but I can't get my N to even get close to a 400-450 RPM idle range. Is this the right rpm range?
Proper RPM at idle??
- Thread starter calh22554
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Varmint1
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Did you adjust the screw on the main throttle shaft on the carb. Also check and see if the butterfly is closing all the way, could be the rod coming off the governer is keeping it on and not allowing it to close all the way
Soundguy
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many are lucky to get to 400.. but way less than 800 should be possible,
disconnect governor rod and see if you can manually get it there. check idle speed stop crew.. not the air needle... ( check that too.. but different test.. )
in to enrich the idle eedle ( air )
out to enrich the man. ( fuel ).
at 850 you are on the main circuit.
disconnect governor rod and see if you can manually get it there. check idle speed stop crew.. not the air needle... ( check that too.. but different test.. )
in to enrich the idle eedle ( air )
out to enrich the man. ( fuel ).
at 850 you are on the main circuit.
Soundguy- you are in to something here. It won't run below 850-900 even when I try it with the Arn disconnected. In fact my idle mixture screw is doing nothing when I try to turn it. I can close it all the way or open it and nothing changes. So is there an easy way to get to the blockage in this jet or so intake the whole carb apart?
Cbrown9064
Silver Member
The reason the idle screw does nothing, is because you are at a RPM where the idle circuit is no longer in play. You are on the main jet at that RPM.
One of two things is happening...1-you have something limiting the throttle plate from closing all the way. Or 2-you have are sucking extra air in somewhere. Like a leaking intake or carb to manifold gasket.
If you don't think you have anything limiting the throttle, spray some carb spray around the intake manifold to block area, and also around the carb to manifold. The engine will slow down if it sucks the carb spray in, and speed back up when it burns it off. A friend of mine had an N that did this and turned out he was sucking air around the intake.
One of two things is happening...1-you have something limiting the throttle plate from closing all the way. Or 2-you have are sucking extra air in somewhere. Like a leaking intake or carb to manifold gasket.
If you don't think you have anything limiting the throttle, spray some carb spray around the intake manifold to block area, and also around the carb to manifold. The engine will slow down if it sucks the carb spray in, and speed back up when it burns it off. A friend of mine had an N that did this and turned out he was sucking air around the intake.
Soundguy
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yep.. grease on the throttle shaft packing or around the carb to manifold will work too.
Soundguy
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it's not a seal like an airlock on a space station.
at idle throttle setting , enough air to idle is getting thru.
that's 'full closed'
at idle throttle setting , enough air to idle is getting thru.
that's 'full closed'
Cbrown9064
Silver Member
The design of the throttle plate in each particular carb factors that in. Some have holes, some have a flat spot in one edge, etc... Cannot remember offhand what your N carb looks like.
If everything is working correctly, you should be able to close the throttle all the way and the engine will slow way down or quit. If you do that and the engine does not slow down, you are sucking air somewhere else.
When you say it dies below 850, what are you doing to cause it to die? Closing the throttle?
Where is the idle mixture set? As the RPMs drop below 850, you will transition from the main jet to the idle circuit. Do you have a N service manual? Set the idle mixture as per spec and start there.
Again, if everything is working correct you will be able to slow the engine down and as it is slowing down you can adjust the idle mixture.
I still bet you are sucking air from somewhere, causing an extreme lean condition the idle circuit cannot overcome. Even at full rich.
Also it is possible the carb has a blocked idle circuit, but you said it was new. Did you check the float level?
If everything is working correctly, you should be able to close the throttle all the way and the engine will slow way down or quit. If you do that and the engine does not slow down, you are sucking air somewhere else.
When you say it dies below 850, what are you doing to cause it to die? Closing the throttle?
Where is the idle mixture set? As the RPMs drop below 850, you will transition from the main jet to the idle circuit. Do you have a N service manual? Set the idle mixture as per spec and start there.
Again, if everything is working correct you will be able to slow the engine down and as it is slowing down you can adjust the idle mixture.
I still bet you are sucking air from somewhere, causing an extreme lean condition the idle circuit cannot overcome. Even at full rich.
Also it is possible the carb has a blocked idle circuit, but you said it was new. Did you check the float level?