F-12 hard to start

farmerphil · Mar 8, 2010

I have a F-12 that is very hard to start. The impluse snaps right at the DC mark. I am using Autolite 3076 for plugs and the mag throws a good spark. Is this the right plug? What is the right way to set the float height? What else could I check? Thank-You, phil

Dave Allgire · Mar 8, 2010

If your impulse is snapping right on DC, I would suggest you relook at your timing. It shouldn"t "snap" until just after TDC as you are cranking the engine over slowly. With #1 on TDC, make sure the pointer in the mag is pointing at the 1:30 position. Don"t move the mag from this position as you are reinstalling it. If the mag drive will not match up, reposition the drive mechanism by removing the two bolts and repositionig the movable driver. I use Champion W14 plugs and have had good luck. Other people might disagree. The float level should be set to 25/32" or 3/4". I measure that from the bottom of the top cover to the center of the float as it is hanging down. That"s a good starting point. You might have to modify that if you get gas running out around the throttle shaft. Hope this helps.

J.J. from Afton · Mar 8, 2010

Because I use my F-12 so rarely I found it helped to put hotter sparkplugs in it for starting and running. I use Autolite 3077s but equivelant champions would also work. Depending how long I leave my F-12 sitting I sometimes have to prime the lines between the carb and fuel pump as well.

-Jordan

Tom Fleming · Mar 9, 2010

F-12's can be notorious for hard starting if they sit for periods of time between runs. It has to do with the fuel supply configuration, fuel pump, carb bowl boiling dry when not running, etc. Hand cranking speed does not actuate the fuel pump diaphram fast enough to fill the carb bowl unless you crank and crank and crank.

I have found that the most common reason for a hard start on a correctly tuned F12 is lack of fuel in the supply system (lines and carb). If the tractor has been sitting for awhile, I always prime the carb with a bit of gasoline. It only has to run for a little bit for the fuel pump to fill the carb bowl......plus F-12/F-14 carbs are VERY finicky.

Try priming to see if your problem goes away before doing anything else. Take the air cleaner hose off temporarily and either put a little gasoline into the carb, or hit it with a couple of shots of ether. If it fires right up, you have found your problem. BTW, I am not saying you don't have another issue, but this one is very easy to check out, and very simple to correct.

IMHO.

Anonymous-0 · Mar 9, 2010

Whatever works. Ask 6 F12 owners how to start them and you'll get 6 different answers. So I'll add my formula. When I restored my F12, I just cleaned carb out good, cleaned filter screen, did not mess with float. Rebuilt fuel pump. Good working fuel pump is a must on F12s IMHO. I use 3077 autolites.
If you start the tractor every week or two, it will start right up. If you let it sit 3-4 months, you may be doing quite a bit of cranking before she pops. I think it's all about lifting the gas up to the carb. Those that have F12-14s with electric start have a distinct advantage. My .02.

F-12 hard to start

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