Carb trouble with H

Farmallb

Well-known Member
It runs somewhat in low speed. It has power even tho running erratically. I plowed a 3 acre field today starting at 1030 A and with a 2 hr break at noon finished at 6 45. This field may have never been plowed before, and I now get where Okies say breaking ground rather than plowing it. IF I open it up, it runs terrible, back fires and has no power. I put a new kit in it last year. Ive had it apart 4 times now, both to spray carb cleaner in it and to blow it out. Ive taken out the fuel bowl, which I had installed a 1in riser pipe in it to keep any scale from getting over the bowl hole. I took it all apart and blowed through everything. Ive got a new filter on it. Ive got it set at 2 turns for each adjustment. I need to get this cleared up as I need to disc and harrow this ground before the fall rains commence. Thanks for any help forehand.
 
I know there's a lot of other possibilities, but the one that stands out to me is your engine is starving for gas. The main needle on the bottom of the carb should be out at about 5 - 5 1/2 turns, especially on a hard pull. Two is where I put it for fartin' around the yard.

Mike
 
I don't pull or plow with my H but 2 turns is too little gas. Mine is set at 3 to 3 1/2 and I only mow and bale (engine driven baler), and I really only hear the throttle open up on hills. Heavy work likely needs more fuel.
The two screws work opposite--the idle screw is an idle *air* screw (backing it out adds air) while the main jet screw is fuel (backing it out adds fuel). You probably knew this but it messed me up when I went to adjust mine for the first time. Back the main jet screw out till it smokes black under load, then tighten until the exhaust clears up. Good luck.
 
I was told the upper screw regulates idle and low speed, and the lower screw regulates high speed. Whats your thoughts on that??
 
On the main jet adjustment screw, the amount of turns mean nothing. You turn it out several turns, open the throttle and then start turning the screw in. When you get to the point where it starts to slow down or die you turn it out until it smooths out and then maybe another half turn out. That might be anywhere from the two turns you say you are at all the way to five turns out depending on what main jet and what needle is in your carburetor.

Idle mix screw again adjust for best idle. Out is leaner on a H idle mix screw as it adds air to mix.

You also mentioned filter. Do you mean an inline filter. If so, you need one designed for gravity feed or better yet, take it out and have a good original type screen in the sediment bowl.

If you cannot get any results with these adjustments, you more than likely have other problems like timing advance if battery ignition or just poor ignition due to many different causes in electrical system.
 
I pulled out the wires from the dist/mag. Had 2 not firing. Ive held my hand on the cap and didnt get my toes curled knocked.
 
As pete 23 wrote, the upper screw is idle air, the lower one is the main jet. When the engine is at low idle, only the idle jet will be providing gas. Looking at the carb, the idle air screw is the brass screw that is on the left side (towards front of tractor), with the head towards the front of the tractor, pointing in the 9 o'clock direction. The low idle *speed* adjustment screw is a steel screw, just above this, and with the head facing away from the tractor (you can see the end of it in the picture). The main jet/high idle screw sticks out at 5 o'clock down at the bottom (slightly cut off in the picture).
cvphoto36358.jpg

The idle air screw can be tightened fully, then backed out one turn. Start the tractor, allow it to warm up, then slowly back out until it starts to miss. Then back in half a turn. Then, adjust the idle speed screw. One way will speed up the idle, the other will slow it down (I forget which is which, but is obvious by listening). I like to run mine at the lowest speed where it is still smooth. Main jet is last to adjust. Tighten, then back out 3 turns. Bring tractor to full throttle, and adjust in until it starts to miss, then out until it runs rich (black smoke). Optimal is somewhere between these. There are videos on tuning carbs by ear that will be more helpful than my directions.
In another response you noted two plugs were dead and had no spark. Adjusting a carb on a engine with only two firing cylinders makes no sense unless it's a John Deere (which only had two cylinders). You have to get all 4 firing first. By swapping wiring between a firing and a non-firing plug (e.g. using the #2 wire to connect the #3 plug to the #3 distributor spot), does the "no spark" move from with the wire? That means wires. if not, then maybe the plug(s) is bad.
If you know you only are running on 2 cylinders, please post, we'll get that fixed first, then move on to the carb adjustment.
 
Dave, It was missing on #1 & 4, Id pull out the wires and that didnt change anything. I had another mag/dist and I replaced them. Didnt get anything. Cleaned up the first one and put it back on. Now, it misses on # 1 & 3. I got a mechanic supposedly coming out with a dwell to check that.
 
Is this mag or distributor ignition? Distributor has an external coil, mag will not.
How did you diagnose the "missing?" By pulling wires one at a time?
 
They both have the black box attached to the top of them with a wire running from the middle of the cap to the box, so, I assume by what you say theyre a distributor. I determined the misses by pulling the wires, at different times, and after switching out the dist, while the engine was running. The sound of the engine didnt change.
 

Factory initial settings, as per a genuine IH carburetor rebuild kit, are 3 turns out for the high speed idle (load screw), and 1 1/2 turns out for the low speed idle. Farmall H and Farmall M are exactly the same.
 
If it is a square black box on top with a wire coming out the back, going to the center of the rotor cap, then you have magneto ignition. This is important as troubleshooting a missing tractor with mag is a little different from one with a distributor. Distributor has a visible, separate cylindrical coil, which should be clearly visible.

If you look inside the cap, do all 4 contacts appear to be in good shape? If so, then move on to the wires. Take a wire from a non-firing cylinder, and swap it out entirely with one from a firing cylinder. You must swap both ends (don't cross wires). Then check again for missing cylinders with the engine running. If the miss moves with the wire, then the wire is likely bad. If not, then move on to the plugs. Swap plugs between a firing and non-firing cylinder. See if the problem moves with the plug, or stays with the cylinder. if it moves, then plug is bad. if the same cylinder still does not fire, then it is something wrong with the cylinder itself.

In an earlier post you mentioned that 1 and 3 weren't firing, then now 1 and 4. This strongly suggests you have a bad wire or two in the bunch at least.

Magnetos require copper core wires. Make sure you don't have any "suppression" wires on there. Those are for use with distributor ignition and resistor plugs. Make sure all your plugs are non-resistor variety as well. Post here with make/model if not sure.

A leaky or stuck valve on a cylinder may also cause a miss, due to lack of intake or compression. However, this problem would not migrate with the wire.

In short, you have to go through the whole thing, carefully and step-by-step to avoid creating problems for yourself if one thing is overlooked. Start with the rotor and wire check, then post back with the results and we'll go from there.
 
Turns out it was the distributor. The tang in the middle of the rotor bug was pressed in. I drove 180 miles to the guy who worked on them before when i lived 10 miles away then. He had a mag repair shop. Now hes old and retired and does it at his home.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top