After cleaning out the fuel system and carb, and putting new mag wires on my D2 pony motor, I've been able to get it running, but I have to use the choke to keep it going at idle. What's the best way to adjust the carb to get it running? Do I work with only the idle adjusting screw, or also with the needle valve adjusting screw?

54D2

There are fuel passages in the bottom of the float bowl casting, did you clean them all out? You have to unscrew the plug and clean out the emulsion / mixer tube also. If they are clean the engine will idle at 800 - 1000 RPM with the choke off and the idle air needle adjusted. Out to Lean in to Rich, sounds like you need to screw it in. Nominal starting point is 1/2 turn from full in.

Thanks for the response. I thoroughly disassembled and cleaned the carb, so I should have all clean passages. I'll check the idle air needle screw. What's the nominal starting point for the needle valve?

Thanks 54D2

Normal for the idle mixture screw is 1/2 turn open. The main should be 1 turn open from closed. The throttle stop screw should be a couple turns open from full closed also. Start engine and tweak idle screw while slowly opening choke. If you end up with the screw all the way in and the choke still closed you have a non cooperating passage.

I had the carb off of a 14 A last week it had a little rust and water had ben in it, Cat still ha sa carb kit amd a float for it, it had been running but now was to the point of no go, the kit had one of the jets and the air mixture tube in it, but one of the passages to the main was plugged and even with air pressure it would not clean out, with some gentle probing with a torch tip cleaner it finally came clean, care neds to be taken so as to not make the passage bigger than it was intended so a small cleaner is used, with 1 1/2 turns on the idle and the main it fires and runs like a charm, before it was the same thing needed to be choked to stay running.

I have rebuilt and adjusted lots of them carbs. and I usually found if the high speed screw was backed out 1 1/2 turns usually was about right and they ran good then but you,ll have to try it and see if that works and tweek it one way or the other a little to get it running right.Never shut the start. engine off with the switch but turn the fuel off and let it burn up the carb. fuel till it stalls out. I do that with my snow thrower everytime I use it and from one season to the other it kicks right off with a couple pulls of the rope after it sets for maybe 8 or more months between spring and winter.

I turned the idle mixture screw to 1/2 turn open, and the motor started and idled great. However, when I opened the throttle up after it warmed up a bit, I could only get the motor to run if I kept the choke partially closed. I adjusted the main jet adjusting screw from 1/2 turn from closed to 2 turns from closed and it didn't appear to make much difference. It seems to run pretty good at the higher rpm's, but I have to play with the choke to keep it going. Any thoughts?

Thanks
54D2

It seems to u

About the only other two things to check is make sure the air cleaner is not blocked up with dirt over the years so try running it without the cleaner on just for testing. Also the float in the carb, needs to be adjusted so when the float is up on the top side ( held upside down) on the housing the float arm should be adjusted parallel with the cover and against the needle and seat just restng against them.If that fails then you still must have some blockage inside the carb.someplace.If the air cleaner appears to be blocked you can steam clean them out by removing the bottom cup and steam down through from the outlet that goes to the carb. and not up through from the bottom where the cup attaches. All the diesel air cleaners that are oil type should be steamed out this way to get them cleaned out and with them there is a couple removable screens to remove by a couple wing nuts so do this first before steaming them so you get all the dirt build up out of them and not collect up in these removable lower screens.

54D2, On the high speed system there are 2 possible basic designs. One is a spring loaded needle that enters a brass jet well in the carb bowl. The other one is a small hollow tube with a very small hole in the side that just enters a cast hole in the carb bowl, this is the early design. If you have the early design the tube can slip in the adjusting screw and never uncover the hole in the side or it can come clean out of the well in the bottom of the bowl. In the bottom of the bowl is a compensator jet that can plug and the main well can also plug. To get enough gas to run both have to be clear. It sounds like the compensator is OK as you can get an idle. Be sure that the needle is indeed coming up from the main jet if you have the later type and with the early one it is very difficult to figure out where the proper range is as about two turns is the total range of adjustment.

If it were me, I would keep turning the main adjust screw in the rich direction, tat is in the direction that will raise the needle, until it either runs or I have the screw in my hand. If the screw comes out then the jet / passage is plugged.

At this point in the process I would have also summoned forth my favorite deity.

On the D2/D4 size pony motor, the high speed needle comes into the top of the bowl from the side, but the needle is still vertical inside the bowl, so there's a bellcrank inside that pivots on a pin in the bowl cover. This can be bent from overtightening the high speed screw and not still be a 90* like it's supposed to be.

But I expect that the fuel passage across the bottom of the bowl from the high speed jet (where the adjusting needle seats) is partially plugged. This is only completely accessable by removing the soft plugs and using a correctly sized drill to clean it. If your seat will come out, you can then get a wire through there and attempt to clean it, but the sure way is to remove the soft plug.

Or you can just learn where to set the choke like I do. Part of the anti-theft system on these old crawlers:D