Hello All, My cousins D4/7U#15195 has a problem with the pony motor. It fires up with the electric starter on the 3rd revolution but then starts to sputter and pop until he get's the choke set just right. As it is now, he has to set the choke almost all the way out to get it to start. Once it starts, he pushes it in just a skosh to get it to run smooth. Even after that, when he goes to spin the main it will sputter and almost die. He then backs off on the clutch, and tries again to engage the main. He might have to do this 2 to 3 times before the pony will stop sputtering and poping and run smooth while turning the main. I told him to let the pony warm up a few minutes before engaging the main. The pony does not smoke, there is no end play on the crankshaft and it burns no oil. He has a new carb for it that his Grandfather, my uncle bought over 16 years ago from Peterson Cat. I'm thinking rather than rebuilding the one on the pony, to just install the new one. This Cat has a 4A blade and 44 hydraulics. The lines run across the dash behind the aircleaner. Do we have to remove the dash to make it easier to replace the carb? Thanks for any help. Joe Giraud

Before he spends a lot of time on the carb, make sure the fuel line is not partially plugged. A lot of times that will cause just what you described. Rusty gas tanks and plugged lines caused a lot of grief with pony motors.
Good luck!!

very likely that if the pony will pull the main OK if you just set the choke correctly, there's not a bad restriction of the fuel, BUT Jim is right, Now is a good time to clean all that stuff out of the tank and lines. Hate to get it in a new carburetor and it soon have the same problem.

I have heard that the root of the problem is a drilled passageway across the bottom of the bowl that is only accessable if you drill out the soft plug that is put in at the time of manufacture. I know I have blown a lot of compressed air etc through there on some of them and it seems open, but still had the problem with needing a lot of choke, so I suppose that may be correct, the way to handle it is remove the plug and clean it with a drill bit or something similar. I have seen some improvement over time on the ones that are run regularly after they have been reclaimed from some "retirement" site.

One other thing you might try initially on the old carburetor before you remove it is to try to adjust the "load" or high speed mixture on the side of the carburetor bowl. Adjust IN to richen mixture. OUT to lean.

There is also the possibility that the linkage crank inside the top of the bowl is bent from over adjustment. It should be a small lever with the two arms 90* from each other. If it is closed up to less than 90* it won't adjust correctly.

You should be able to drop the float bowl off with out to much problem.
Take it off and see what you got, then clean and reinstall if it doesn't look to bad.

Muzz

Joe;
I agree with ccjersey, had similar issue with my pony and after a complete carb rebuild, and no success, an old time carb person said there is a fuel passage on bottom of bowl which usually fills with dirt/sediment etc. We used a strand of copper wire and fished through passage several times to loosen and eventually flush out sediment. After this pony started and performed great. However, my pony is very sensative to choke adjustment/setting.

Joe,
I have a D4-7u that the only problem I have ever had with {either engine} is bad gas in the pony motor. The gas seems to go bad very quickly. Most of the time if I just drain the gas tank and refill it, it will start right up. Occasionally I have to remove the carb and clean it. {I don't recall the passageway on the bottom} I think the rusty tank somehow speeds the gas going bad. It will usually smell like varnish. If I smell the gas and have any doubt at all, I change the gas. If I am not going to run the cat for more than a month, I drain the pony motor gas tank. I have replaced tune-up parts, replaced carb gaskets {I think that's all there is in a rebuild kit} and the problem is always the gas or at worst I need to clean out the carb. I probably have had this problem 10 times in the last 7 years or so. {my cat is not used regularly}
Usually it just won't run, but I'd sure check this before you do any other work or spend any money. I wasted alot of time on mine when the problem was easily fixed. This has happened within a month or two of fresh gas being put in the tank, so If I have any doubt at all I change the gas, regardless of when the last fresh gas was.
Frank

I cleaned my pony tank with muratic acid then lined the tank with Kreem
tank sealant. going on 3 years and have not noticed any problems with the
liner.

Thanks guys. I'll tell my cousin to check for all the things you all listed. Have a nice upcoming weekend. Joe Giraud

To removed the pony motor carb on my D47U, I only removed the hood. Mine has the same hydraulic lines around the back side of the firewall as yours. To make room for the 1/2" wrench on the carb base's right nut, I removed the pony motor governor and left it hanging on it's drive belt. The carb was then able to be completely removed in one piece. As you remove the carb, don't drop the lock washers down the intake manifold. I almost did. The dirty carb was cleaned in carb cleaner and reinstalled. I didn't run a wire through the lower float bowl passage as was suggested because air passed through the passage quite nicely. After putting it all back together, it still needs full choke to run. Drat! Tomorrow is another day and apart it will come.

Here is a thought. Did you remove the plug in the side of the float bowl and get all of the crud out of that mixing tube? It probably will no longer unscrew from the well either. The outside area of the mixer has to be clean also. The Serviceman's Reference Book or the Operations and Maintenance Instructions book has diagrams of the functioning of this carb.