Super A tune up

Goodman · Jul 27, 2011

finally got all of front end back together and fired up my 51 Super A. Seems to run fairly good with small pop every so often. Feel pretty good about timing but want to do some adjustment on carburator to get it just right. Any advice on adjustment steps, which mixture screws to with first, low idle speed, etc. Any advice here greatly appreciated.

Thanks guys

JRSutton · Jul 27, 2011

I haven't done much with farmall carbs, so I'll leave that to the guys here who have.

However - if it's popping, I'd think your problem is more valve and/or timing related.

gene bender · Jul 27, 2011

Your carb should only have an idle mixture and that wont stop the poping. Have you checked the valve clearence and do you have a mag or a dist.

Goodman · Jul 28, 2011

the Popping is very suttle. And yes I have checked the valve clearance, fresh rebuild. Ran it a little while and checked them again. I just eyeballed my timing but would like to know it is right. Should I just adjust it slightly and run again, trial and error, or is there a better way?

Goodman · Jul 28, 2011

I have a Distributor.
I have two adjustment screws, one on the bottom of the bowl and one on the intake of the carburator. I thought the upper one was mixture, what is the other one?

Thanks

rustyfarmall · Jul 28, 2011

(quoted from post at 05:44:13 07/28/11) I have a Distributor.
I have two adjustment screws, one on the bottom of the bowl and one on the intake of the carburator. I thought the upper one was mixture, what is the other one?

Thanks

The upper adjustment screw is the air/fuel idle mixture.

Bottom screw is for adjusting how much, or how little gasoline can actually get into the engine. I don't have the specs handy, but I would think that bottom screw should be turned in until it seats, then turned out maybe 2 full turns. The number of turns out will be determined by how the tractor is used. If it needs full power most of the time, that screw might need to be turned out even further. If you just putter around, 2 turns should be sufficient, or maybe even less.

JRSutton · Jul 28, 2011

Sorry goodman - I did say valves/timing at first, but I answered too quickly. Since it's a fresh rebuild, and you've adjusted the valves - You were right, it could (almost certainly) be that you're running a little too rich or lean and not always getting a full burn in all cylinders.

with no air cleaner in place, if it pops out the carb, the timing might be advanced too far.

if it's popping out the exhaust (or even both carb and exhaust), it's more likely a bad air/fuel mixture.

Not hard and fast rules of course.

Goodman · Jul 28, 2011

Thanks, I don't have any backfire out the carb, only a small pop out the exhaust but no smoke. I still think it is fuel, will play with some.

Goodman · Jul 28, 2011

Thanks for the info on the bottom screw, wasn't sure what it was for. Two rounds out is where I had it set.

Super A tune up

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