[deereman84]

I have a 318 with an P218 in it. It runs great and doesn't use any oil. My issue is that I am not able to adjust the idle speed down to where the manual says it should be. It is very happy idling along at 1700 RPMs. The screw on the front of the carb does not effect the idle speed or even cause the engine to change at idle. I have the service manual and have followed the procedure but can't seem to get the idle down. I have backed off the idle speed screw on the throttle cable so that isn't stopping it. I know this seems petty since it runs just fine but now it is just annoying.

 

[doug_phelps]

Hey Jeremy...

It sounds like your needing to adjust the governor and idle setup. Specifically the governor spring setup.

Has the throttle cable been replaced? Perhaps someone never adjusted the setup at that time and it is holding the idle high?

While it might run fine - at throttle down and shutoff - I'd be worried about excess fuel being left in the cylinders and backfiring through the intake. (all kinds of bad things can happen).

 

[wmgeorge]

You might have an air leak someplace. How long have you had the machine and has this always been an issue? Just wondering if a previous owner might have replaced either the carb or internal parts.
I don't think either the throttle or governor are even operational at idle.

 

[deaddeere420]

Jeremy
How are you checking the RPMs?
Are you using a tach made for a car?
If so you have to divide the RPMs in half
I just ran into this problem with my 420 and it's P220. The Onan engines fire the spark plug with every rotation including the exhaust stroke. This cause a normal tach to read double over what the actual RPMs are.
Here is a link to the thread where I had the same issue and the answer
http://www.wfmachines.com/discus/messages/17/287810.html?1402319260

 

[900thun]

Is it possible your governor linkage is the problem? I'd probably disconnect the rod that goes from the carb to the governor to at least make sure.

 

[deereman84]

The 318 only has 800 hours and it is all original. I have had the heads off and decarboned the pistons and valves last year. Cylinder compression is at 130 PSI on each side so the engine itself is strong. I have a Tiny Tach mounted on the dash that gives a constant RPM reading. I haven't checked the throttle cable yet to see if it has moved.

 

[900thun]

Sounds like a nice 318. I ordered a unit yesterday to check all of my machines rpm at idle and full throttle.

 

[deaddeere420]

what rpm does it read at max throttle?

 

[deereman84]

At max throttle it reads right around 3450.

 

[hankvc]

Jeremy, the first place I'd look is at the throttle linkage. Disconnect the rod that goes to the carburetor throttle arm. With the dash throttle all the way back, pull the throttle arm against the stop, and replace the rod in the first hole that will hold the throttle against the stop.

Also, check the carburetor throttle shaft for fore-and-aft play. Should only be a few thousandths. Air leaking past the throttle shaft will cause the minimum idle speed to rise. However, I think the throttle shaft would have to be almost falling out of the carb body to give you 1700 RPM. You need to be sure that the linkage is pulling the throttle all the way closed.

Hank

 

[deaddeere420]

if max is right, and yours is
you don't have the same problem I did

 

[Hammerdown-7]

Hello Jeremy
Is the P-218 original to the Tractor ? The reason I ask is that my 1983 John Deere 318 had a B-43-E Onan in it and it had a Idle down Dash Pot solenoid that was mounted on the rear air filter cross bracket. if your Tractor has one of those check to see that it is adjusted right as they can keep an Idle Higher if they are not adjusted right, and if they fail in the Outward Position it would keep your idle speed higher. They are supposed to be set with a Feeler Gauge with the dash Pot clearance being 0.050" with it resting in a closed throttle idle position and it is critical to have them adjusted correctly or your engine will idle higher and not idle down even when you adust the slow idle screw.


If you do not have the Dash Pot solenoid I would check your Governor throttle plate bracket that is mounted on the top of the engine. It has a Bent 90 Degree Lip for High Speed maximum Position of throttle lever throw as well as an idle position. If that Lip is Not allowing the Throttle to return to an idle they say to use a set of Pliers and bend it some so that the throttle Plate Lip does not come in contact with the Throttle lever when coming down to an idle. I hope this helps, Kurt