8N once more

2. I said it throttles up fair...if I pull the throttle wide open quickly it sputters, engine goes to full throttle but the governor still "hunts" and the engine just does not run smooth,
[snip!]
If I move the throttle lever up to wide open slowly (one slow continuous movement) it runs right. It only surges if I go into WOT quickly.

This sounds like a governor problem to me. By suddenly opening up the throttle, you create a situation in the governor that is undamped oscillation (like a car with bad shocks - it will continue "bouncing" up and down much longer than it should when you push down on a fender suddenly and release) so it "hunts" meaning that it is OVER CORRECTING in each direction, slow engine RPM - open throttle, fast engine RPM - close throttle. These happen fast enough to simulate what you did to start the "hunting" [undamped oscillation], but does not happen when you open the hand throttle slowly, because you have not forced the governor to over correct.

I would check your governor for a grove in the cup, or wear else where.

Been "beat up" more than once trouble shooting computer problems that were two or more failures. They got really tricky when one failure was tied to another one so that the symptoms of one masked the other. Wish I had some good words of wisdom to help you. In my case, I usually had to resort to writing down what I did and what was the result, every step along the way, eventually a pattern would emerge that gave the solution.

Good luck, let us know what you find.
Larry

Governor problem... the engine will settle down, and with a very slight movement of the throttle rod, you will be able to maintain a steady engine speed.

Carburetor problem... the engine WON'T settle down at a steady speed with the throttle rod to the carburetor "stabilized" by hand.

I think he said that he put the smaller (hole) in to the MAIN jet location (under the nozzle) ...and that would be wrong!

JMHO

Ok, here is my question re-phrased,I have searched and read the archieves and read the repies about carb adjustment. I have a good understanding about the adjustments. I DO question my putting the main jet in the right place. Here is a picture from Don Stewarts article (a good one too) on rebuilding the Marvel carb. This picture shows the main jet somewhere in the rectangular hole in the lower housing. I put it in the same hole that the main nozzle goes. Did I put the jet in the wrong place or is this picture misleading? Thanks for the help guys.

Zane

I need to get a better scan. For now, I put the part names next to the unreadable key numbers, refering to the original copy, for the part names.

Ford Owners Manual sez to set BOTH the idle mixture and the main jet to 1 turn. Well that works on a new carb on a new engine. I don't think your tractor qualifies. Therefore, I suggest 1-1/2 turns for both the idle mixture and the main jet.

After you get your engine started and fully warmed up (about 15 minutes). Adjust the idle mixture for MAXIMUM rpms, not maximum smoothness, understand? max idle rpms. Tractor idle spec is 450 rpms which is awfull slow to our ears. If your carb is anywheres to being right, you can do it.

Now then, goose your throttle, if engine doesn't respond, enrich the mainjet 1/8 turn. Do it again. You may have to go out to 2 turns on main jet, but no more.

Learn how to read your sparkies color. After idleing for 15 mins, pull a plug, it should be a light tan or light gray color. If it is sooty black your too rich. If it is clean white your too lean. But most important, adjust idle mixture for MAX rpms. Now go mow or plow for a few minutes at high rpms, and pull a sparkie and read the color. That will tell you how well you've adjusted your main jet.

From the black art of adjusting carbs..... ...Dell

Start with both mixture screws about one turn out from lightly seated. Start the engine and adjust idle mixture screw (small screw near where carb attaches to the manifold) for smoothest low-speed (around 400 RPM) idle. You should adjust the idle mixture screw by slowly turning in until engine stumbles (too rich) and then turning out until the engine smooths out. You may have to back off the idle stop screw (the one where the linkage connects) if the engine speeds up too much after adjusting the idle mixture. If so, readjust the idle mixture screw.

This carb does not have an accelerator pump, so you want the idle screw set right at the point it smoothes out from being too rich, rather than centering between too rich and too lean, like you would do with most automobile carbs. If you set it too lean it will stumble like you describe when you quickly advance the throttle.

Only after you get the idle speed and mixture correct do you adjust the high speed mixture screw (large knob at the opposite end from the air inlet). In a perfect world you rev the engine up to rated speed (1500 RPM or about 3/4 throttle) with a good load on it and turn the screw in until it stumbles then back off until the engine smooths out. I don't have any way to do that safely, so I start with the bench setting and adjust by turning the screw in 1/8 turn at a time and putting a load on the engine. As soon as I detect any stumble, hesitation, or backfire when picking up load, I turn the screw back out 1/8 turn and then leave it alone.

Any vacume leaks? It might be continually lean..

Soundguy

Idle and main jets are not the same size externally. I am confused by both the picture I posted concerning the location of the main jet and also the folowing statement in Don Stewart's article: "Next to the float seat is the idle jet seat. This is the jet into which the idle screw/needle fits when the carburetor is running on your tractor" Knowing that the idle mixture screw is installed from the right side of the carb makes that statement confusing. Actually the tractor runs pretty good with the high speed screw out about 6 rounds but I am the kind of guy that wants to know why mine has to be out so dang far to make it right.

Try the propane or ether trick to check for vacume leak...

The fact that it doesn't seem to be running rich with the main needle out that much means that it either isn't getting all that fuel due to the clogged jet or the obstruction.. or that the mix is so lean.. that it needs that much enriching to work ok.. that's my uneducated guess and 2 cents anyway...

Soundguy

Very ocasionally I get debri that the spray carb cleaner won't cut.. but the dip style cleaner cuts easilly.. though I'm sure you've cleaned it good... just mentioning it.. etc.

Soundguy

Soundguy

soundguy