F-12 power loss and shake

Anonymous-0 · Nov 22, 2012

Got my F-12 running a couple of weeks ago. Engine was loose, rebuilt magneto, carb, fuel pump, new spark plugs, magneto timed, set valve lash hot, points set to .013", spark plugs gapped, etc. Ran great for the first few hours, but now it loses power going uphill and shakes at higher rpm. Adding choke for more fuel does not help. The shake at high rpm also happens when out of gear and also when clutch is pushed in so it's in the engine. idles just fine and got spark to each cylinder and no exhaust smoke. I'm out of ideas and would appreciate any thoughts. thanks!

Janicholson · Nov 22, 2012

Try this simple test. Pull off each spark plg wire at the plug and use a cloths pin to clamp them so there is a 1/8 gap between the clip and the plug tip. This causes the voltage to go up and partially fouled plug to fire. (easy to try, and indicates the need for cleaning the plugs.) The newly started tractor could be causing that.

Bill Krosnicki · Nov 22, 2012

As far as loss of power is concerned, probably some crud or rust broke loose in the fuel tank and is blocking something, first thing I'd check is the screen on the sediment bowl. For the shaking, seems like something loose like the flywheel or something in the clutch. Unless it's shaking because it's missing. You may want to double check the valve clearance as they can loosen up after it runs awhile.

John M · Nov 22, 2012

Be hard to do that on a 12. The yhave ring terminals, not rubber boot type wires.

John M · Nov 22, 2012

What plugs are you using?

Janicholson · Nov 22, 2012

Oh well there is a way, pull them out of the cap a bit. OR A tab of duct tape to place them in the 1/8th gap at the plug will also work. Jim

Anonymous-0 · Nov 22, 2012

Thanks for all the ideas, especially Janicholson. I pulled all the plugs and cleaned them up. They didn't look fouled, but I made them shine. Then just because I had the plugs out I slow rolled the engine by hand and put my thumb in the holes for a very crude compression test. All seemed good. Fired the F-12 up and it runs much better. Power is fully returned and shake is diminished but not gone. I think I'll replace the spark plug wires (using wires with the cloth insulation and ring type attachment that came with the tracotr). I am using Champion W20 plugs. I'll also figure a way to set the 1/8" gap on the tip of the plugs to make the spark really jump and develop hot voltage. Thanks again!

Ron W · Nov 22, 2012

I have had nothing but trouble with the modern Champion plugs. The new plugs are porous, a guy once told me that they no longer glaze the ceramic portion that is in the engine. I have been using Autolite 3076 I think. They seem to be better.

Janicholson · Nov 22, 2012

That is just a test for fouled plugs. So just temporary. It is easy with a tab of Duct tape. Jim

F-12 power loss and shake

Anonymous-0

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Janicholson

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Bill Krosnicki

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John M

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John M

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Janicholson

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Anonymous-0

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Ron W

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Janicholson

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