f12 finally running, need help fine tuning

F12 guy · Nov 23, 2012

Ok I finally got my f12 to crank and run. I have a couple questions. She will crank between the 3rd and 10th crank most times. After adjusting the valves and carb. after the motor has run 20 min like operators manual say she seams to run fine just seating at a ideal and full throttle. When I drive around she will act like she starving for gas just a little or missed fired on one cylinder. It's hard for me to tell. I can drive up a hill in 2nd gear and governor opens up and she will pull on up hill so this makes me think the timing is right or close. I have not changed timing since i put mag. On and timed it then. Could the carb. Load screw be to far in? I don't understand how she will pull up hill if screw is not out far enough. Could timing be off just a little? Any help welcomed thanks Josh in NC
PS every thing in mag. Is new and carb.has been rebuilt.

Nebraska Cowman · Nov 24, 2012

The easiest way to find out would be to open the screw a little. Just keep track how much you turn it so you can put it back if it does not help. If it starts that easy with the hand crank I doubt the timing is off very far.

Dave Allgire · Nov 24, 2012

Cowman is right. Keep track of your fuel adjustments. If the fuel adjustments don"t do it, re-check your timing. When everything is right, it should start with no more than three pulls on the crank. My $.02 worth.

Craig45 · Nov 24, 2012

One of my F12's seems to run fine in the shed but acts up when in the field. I don't know why this is so, but it seems to run much better with the gas tank at least half full.

F12 guy · Nov 24, 2012

That's for the replies, I'm going to try adjusting on carb.this morning. I was thinking last night that maybe float could be to low making her starve for fuel. Could being a 32nd low make that big of a difference?

Dave Allgire · Nov 24, 2012

Sounds to me as if you have a weak fuel pump. I don"t know what kind of setup you have but, there are two different kinds. One is a fitting in the front of the fuel tank with a restrictor back into the fuel tank. This is usually found on a gas only rig. The other is a Fuel vent that sticks up through the hood. This allows the excess fuel the pump puts out to return to the suction line of the fuel pump. Either way if you have to have a 1/2 tank to run in the field, I would suspect a weak fuel pump. It is a very, very, low pressure pump. It could be anything from a diaphragm going bad, to bad check valves. Rebuild kits are not that expensive. I would try that. Another thing to check is the float level.
With the top of the carb off, check the float level. With a gasket held in place, measure from the gasket surface to the center of the float. The book calls for 25/32". 3/4" is close enough. Adjust accordingly by bending the tab on the float assembly CAREFULLY. Since you will have the top of the carb off, check the screen at the input to the carb,too..

f12 finally running, need help fine tuning

F12 guy

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Nebraska Cowman

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Dave Allgire

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Craig45

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F12 guy

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