![]() Fill the ony motor gas tank with regularf petrol only. Now start the main engine by simply opening the throttle. The oil pressure gauge will register oil pressure and the fuel pressure gauge (on the front left side of the engine) will go to the green. Overview with the breather off the Pony motor. The spark plugs D16 are the same as the seagull outboard motors for boats and readily available in NZ. The sediment bowl sometimes you can use an old pill bottle but the problem can be the top of the bowl housing has corroded over the years. Breaker points will begin to open, Install. Take magneto out & plate & rotor off then rotate magneto drive gear until rotor contact in line. Crank on No1 is now 25 ahead of TDC on compression stroke -firing point. Continue until the mark or is even with the mark on the start engine crankcase cover. Take out spark plug & check piston is coming up on the compression stroke. 20 Open cylinder head drain bolt at the rear of the magneto and below it & turn flywheel. Magneto number made by Bosch in Massachusits, USA very rarely you have a problem with but still check. Check coil & condenser in the magneto and test for spark before you put back as this and the carb are normally the headaches in the Pony motor Magneto in the pony motor Caterpillar D4 Bulldozer- easy to get out and easy to check but make sure you line up the timing marks (you normally need a good torch to get TDC). Remember we are back yard bush mechanics!!! We will change to auto start this machine and show you how to do. The pull rope start is a headache- you start it clockwise. ![]() Especially when starting in real cold weather this is important. Once awake you need to keep the Pony running until the water heats up to the main motor and the head at the rear of the main motor is warm. Remember this bulldozer does not use a battery as the magneto does the work of the normal distributor and spark etc. We then managed to fire the Pony motor up OK Still the pony motor once started was running on 1 cylinder but then we stripped the magneto again and saw the offset shaft which caused the problem & then the condenser being the main cuplprit so check these as its normally the magneto or fuel you will have the problem with. One plug was hot the other cold but we found the problem in the magneto & points. You will see the timing marks once the magneto is out. We got spark in the magneto and set the timing OK (bit hard to see timing marks so make sure you have a strong torch to see and try to mark if you dismantle). In our case it we had one spark plug good and the other cold- tried leads & switching spark plugs as we didn't have any spares at the time (this machine was in the bush). If you have problems with spark check each of the 2 plugs once the motor starts but also start the pony with spark plug arcing against metal to check for spark. With us we had intermitten spark problems and it turned out to be the magneto shaft not centred & the condenser which although we gor spark we only just got it. Makde sure you have fuel flowing thru the fuel lines to the carb bowl. Clean the bowl & blow the air thru the carb line and bowl if sitting. The D4 can give you problems especially when sitting a long time. If access to air line take the plugs out both sidse & blow air when you crack 1/4 turn taps to release water etc. Drain plug is on the right side if in the drivers seat. Check dip stick & use SAE30 grade oil to replace or top off. Note in the above picture: the tap at the bottom turn 1/4 turn only to release any water if sitting on both sides of the pony motor. The older D-4s have the same carb kit as a John Deere JD 720 and 730 pony motor The Pony motor carb kit: CAT part number or better yet the Zenith carb number should be a Zenith K2067 kit. ![]() The Pony motor started the machine then the diesel engine kicked in once primed by the petrol -powered motor. The smaller D2 was a bit underpowered for the weight but the D4 was another machine and solid as. The Caterpillar Company continued to build new D4s right up till now and they are a great machine. The D4 actually started around 1937 with a G4 Series then evolved into the 7U Series of the 1940s and 1950s.
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