Cat D4 U7 Pony Motor Problems Any Help Much Appreciated

Governor problem. Reach across and see if you can push the governor arm which is connected to the throttle butterfly and get it to speed up.

If that's not part of the problem, have you drilled out any of the plugs and truely cleaned the carburetor passages? You can usually compensate somewhat if you run a lot of choke to help it pull enough fuel, but when it's right, its a dfferent "critter "!

Have you swapped the spark plugs for new? Wondering if it is firing on both cylinders?

Thanks for your information. I did play with the govener arm and it didnt seem to make any difference.
I will pull apart the carby and drill out the plugs etc.
Do you know what the correct spark plugs are to suit this?
Is there a set of points in the magneto that may need cleaning?
It seems to be firing on both cyclinders as both spark plugs get hot.
It did rev out once for me but wouldnt do it again.
Thanks Phil

Like CCJERSEY said check your governor first

Recently one of my D2 ponies (same engine as yours) was not revving up. I checked all the usual suspects like the jet in the bottom of the carb bowl, spark plugs, mag firing. All that was fine. Governor hadn't changed. Finally I took loose the fuel line and found there was just a trickle of fuel coming out of the line at the carb. Tracing it back what I found was that the metal fuel line at its lowest point was almost totally clogged. I removed the metal line section between gas tank and shut off valve and used wire to rod it out real good. After that the pony started and ran like a top. And even better because I had cleaned the carb jet and did other maintenance stuff during all the trouble shooting.

But you say there is plenty of fuel. Just curious, did you remove the fuel line to the carb and verify fuel flow?

Yes, the mag has a condenser as well as points. And it has a coil.The condenser is just a capacitor there to help keep the points from arcing so much and burning up quicker. The condenser could dry out or short. But you have spark. The magnet in the magneto could be weak. Or, the coil generating the spark could be weak. I had a pony once that would start and run while cold and then not run once the pony was hot. Ended up being the coil in the magneto. It was breaking down when hot. If you have good blue spark, it kind of rules out the magneto. I might be wrong though, but it seems your problem should be a fuel issue.

I'm going to agree with Arthropod, reason is that if it has enough fuel to run, it will crank the main even if the throttle on the Pony is NOT wide open.
They take longer to start but do start.
This gives me the impression that you are lacking power???
You look down the carb with it running....said choke and throttle are wide open.
Seems to have good spark......I thought maybe Mag timing issue but that usually carries a whole other set of issues.
Basically this leaves Fuel delivery.
BTW, Have you noticed when changing around sparkplugs are they grey/white tipped or kind of sooty/black?

As far as spark plugs go, a lot of people on this site Including me say to go with NGK brand plugs. I Installed NGK 2910 plugs on my D2/3J pony back in 2007. They are still doing the job. If you have a later model D4/7U with the higher compression pony heads they might take a different plug number than the older pony heads. Remove, inspect and clean all pony fuel lines to make sure you have proper fuel flow to the pony carb. Good luck. I'm sure you will find the problem and be "Cattin" in no time.👍
Joe Giraud
1940 Cat D2/3J#4103
1941 Dodge WC-12(Salad) Military 4x4
San Carlos, CA

Look at the spark color. If it is yellow, you need a new condenser. Check the point gap while you have the cap off. .016 If you have a Bosch mag, remove the condenser, and carefully drill out the spot welds on the bracket, clean the bracket well, tin it with solder (acid core), and carefully solder it to a new condenser, (Napa p/n RR174) using as little heat as possible, with a small soldering iron. (like a Weller) Cool it immediately, to prevent interior damage. BTDT

I'm going to agree with Arthropod, reason is that if it has enough fuel to run, it will crank the main even if the throttle on the Pony is NOT wide open.
They take longer to start but do start.
This gives me the impression that you are lacking power???
You look down the carb with it running....said choke and throttle are wide open.
Seems to have good spark......I thought maybe Mag timing issue but that usually carries a whole other set of issues.
Basically this leaves Fuel delivery.
BTW, Have you noticed when changing around sparkplugs are they grey/white tipped or kind of sooty/black?

[quote="drujinin"]I'm going to agree with Arthropod, reason is that if it has enough fuel to run, it will crank the main even if the throttle on the Pony is NOT wide open.
They take longer to start but do start.
This gives me the impression that you are lacking power???
You look down the carb with it running....said choke and throttle are wide open.
Seems to have good spark......I thought maybe Mag timing issue but that usually carries a whole other set of issues.
Basically this leaves Fuel delivery.
BTW, Have you noticed when changing around sparkplugs are they grey/white tipped or kind of sooty/black?[/quote]

hi thanks for your advice,spark plugs are black,choke off,add ether and no differance,i will fit new plugs,clean out tank fuel lines and carb and try again,i will also check and clean points,16 thou,other than that im kinda lost.