7U Series D4 starting engine carb & mag settings?

before all that kit work, make damn sure the gas tank, line and carb bowl is clean. carb bowl is an easy take off, leave the cast throat body on.
easy stuff first and these are the most common problem when "the machine was running last year."
oh yea nice looking drawbar ag tractor, no hydraulics..... thats really barebones, hard to find them that nice. mustbe california

[quote="ag-mike"]before all that kit work, make damn sure the gas tank, line and carb bowl is clean. carb bowl is an easy take off, leave the cast throat body on.
easy stuff first and these are the most common problem when "the machine was running last year."
oh yea nice looking drawbar ag tractor, no hydraulics..... thats really barebones, hard to find them that nice. mustbe california[/quote]

I'm with ag-mike on this one, keep your repairs real simple first. Like remove the top cover over the fuel bowl on the pilot motor carby and blow out the crud in there with compressed air, follow by a good soak with some Carburetor cleaner in there, then blow that out.

While the gas line to that carby is not connected make sure you have a real good flow of clean gas (discard the old gas in that gas tank), and, that your float valve/ jet is openning and shutting properly, then bolt the carby back together. Before replacing the points and condensor in the magneto just clean the points first with a nail file or doubled over sand paper or similar tool, then a final clean with some paper gently gripped by the points when they are closed. Clean inside the magneto cap with gas or carby cleaner.

From memory the points gap is around 12-14 thou, make sure there is no obvious corrosion on any of the electrical fittings inside the magneto, and that your spark plug wires and spark plugs are in good condition. If that pilot motor was running when the tractor was last used I'd be surprised if it wouldn't run again after those basic house keeping tips.

The pilot motor carbies (and pilot motors) are very rudimentary and the rubbish gas sold these days causes more problems in the carbies I believe than wear and tear, most those little pilot motors just don't do enough hours to warrant the expense of a carby rebuild kit, as there are some internal passageways that could block over time, and a new kit does not fix that problem.

That scenery behind the tractor reminds me of Arroyo Seco, up above the Salinas Valley, good quail hunting country!😆
Good luck
Mike

This is in south-east Idaho. There is some good quail and grouse hunting (and so on up to Moose) but I live 90 min south in Utah and can't afford an out of state permit.

There used to be a front mount hydraulics pump on this machine but it was hard to keep going and my dad sold it when we bought a new D4DSA about 40 years ago. Mayby 5 years ago my brother cracked the D4DSA oilpan on a rock and didn't catch it before pounding the bearing on the #1 conrod. It was cheaper to by a similar age D6B than to fix the D4D, so it sits.

The farm has been (and still is) in a conservation program for nearly 30 years but my cousin has an adjoining 165 acre piece coming out of the program that I want to try to farm.

In 2007 I did a valve job on the starting engine. There was no compression on one cylinder and one of the valves wasn't closing. I bought all new valves, springs, etc. When I tore into it it turned out that it was just a bent retaining clip, but I went ahead and replaced all the parts since I'd bought them and had the engine apart. It ran well after that.

We've cleaned the little gas tank several times over the years, including this year. One year I even took it into work and sand blasted the inside. We have even spliced an inline filter from NAPA about 6" ahead of the carb bowl. The filter is not stock so the purists might not approve but it has been helpful.

This spring I was dismayed to find the fuel valve open. I though everyone knew better. Still there was no gas in the float bowl even though it flowed freely to the carb. The float needle was sticking. So at that point I tore the carb apart and used a big can of spray cleaner to blast all the passages. It was clean. However the main metering jet screw was loose and I didn't know how many turns out to set it. We tried for a couple of hours then gave up.

Next we took on my cousins 5U series D2 that hadn't run for >10 years. It's gas tank was badly rusted. We put gas and a box of sheet metal screws in the tank and shook it for a long time, then drained, and as the shampoo bottle says rinse and repeat. We added the NAPA filter to this machine, did a quick clean of the carb and this machine fired right up.

I think there was a pencil written note on the D2 engine with the date that the mag points and condenser were changed which led me to think about replacing those parts on my D4.

I found this site for magnetos http://www.magnetoparts.com/ and it's owner
Bill Lopoulos replied with the points setting.
.015 for the points, .025 for the plugs.

So now the carb float setting (distance hang down from lid - adjusted by bending tab) and the mixture screw turns back out from all the way in are the main bits of info needed.

These old machines have such a sweet exhaust note, something I think even the Harley owners would envy.

Thanks,

Joe

as reads from the d4 reference book. the float level is correct when a measurment of 1 1/8" plus or minus 3/64" exists between the face of the cover of the fuel bowl (without gasket) and the bottom of float.

carb adjustment approx settings from all the way seated. back of the high speed screw one turn from closed and the idling screw one half turn.

Remember, to richen the mixture (either the idle mixture or the high speed mixture) turn the screws IN. This is exactly backwards from most small engine carburetors.

If by some chance your high speed mixture screw goes into the fuel bowl vertically, it will adjust normally (IN to lean, OUT to richen), but most are horizontal to clear the pony motor tank.

All the pony motor carbs have the idle mixture set by bleeding in air to dilute the gasoline coming through a fixed orifice. So turning the screw out lets in more air and less gas.

The high speed mixture is backwards because of the linkage underneath the carburetor bowl top that comes with the adjustment screw being horizontal. The fuel metering needle is your standard needle/seat arrangement, but there is a little crank there to translate the motion of the horizontal screw to the vertical needle.

[quote="ccjersey"]All the pony motor carbs have the idle mixture set by bleeding in air to dilute the gasoline coming through a fixed orifice. So turning the screw out lets in more air and less gas.

The high speed mixture is backwards because of the linkage underneath the carburetor bowl top that comes with the adjustment screw being horizontal. The fuel metering needle is your standard needle/seat arrangement, but there is a little crank there to translate the motion of the horizontal screw to the vertical needle.[/quote]

Very interesting. You know as an engineer I should be more observant and figure these things out for myself, but sometimes it is hard to see past your own assumptions about how things will behave.