Disassembling of a Hitachi carburetor for a 1975/1973 Datsun 620 truck, DCH340

This post is to document the disassembling of a carburetor for my 1975 Datsun 620 truck. I am assuming I currently have in my possession a Hitachi DCH340 Carburetor that was originally equiped on a 1973 Datsun 620 truck.

I purchased the 1975 Datsun 620 truck with an unknown carburetor installed and running. There are no numbers on the carburetor for me to cross reference it to a part. I ended up buying a used one from a wrecking yard and I removed it from a 1973 Datsun 620 truck. After doing some research I concluded that I needed a carburetor gasket kit for a 1973 or 1974 Datsun 620. I purchased the one for a 1973. Please view this post for information on how I got to this conclusion.

NOTE: I will be giving some parts wrong names (to the best of my habilities), but close to what I want to describe in the pictures. I am new to carburetors so if you read any misleading names or information please let me know.

Figure1: Carburetor side view A

 In figure 1 two main parts are facing towards the camera: the carburetor choke pull off, and a temperature/pressure operated valve (of some sorts, please give it a name, evaporator perhaps?). There is also an idle solenoid attached to it.

Figure 2: Carburetor side view B

 In figure 2 the fuel filter inlet tube, fuel bowl (screen), and replaceable pump (on the left) are visible facing the camera.

Figure 3: Carburetor side view C

 In figure 3 the throttle linkage is visible. This linkage is composed of a main bracket directly attached to the top cold starting butterfly (throttle used for cold starts). It also has a thick piece of wire attached to the main bracket on the far left, a spring pulling the main bracket down, the replaceable pump on the far right. An adjusting screw is visible below the main bracket, on the bottom piece of the carburetor. Also, note that this bottom piece, or "feet", have to vacuum tubes coming out of it. One is plugged, and the other one runs somewhere to the engine.

Figure 4: Carburetor side view D

 Figure 4 shows the diaphragm chassis or enclosure, the choke pull off (looks like a fuel pressure regulator on modern cars), and the automatic (electric) choke.

Figure 5: Carburetor top view

 Figure 5 shows the top of the carburetor. Nothing very special here.

Figure 6: Linkage for throttle E

 Figure 6 shows throttle E shaft attachments. I am calling throttle E the throttle plate attached to the throttle shaft viewed here, the one attached to the bracket where the throttle cable attaches to. Also, in this picture one of the adjusting bolts is visible.
Linkage F will be the one where the the diaphragm link attaches to.

Figure 6-a

 Figure 6-a shows another view of the throttle shaft E attachments.

Figure 7: Lock for the Main Bracket

 This pictures show the parts that came off the main bracket throttling shaft, the shaft where the main throttling bracket pivots on. It shows the parts and the order in which they were removed.

Figure 8: Throttling linkage, thick wire parts

 Figure 8 shows the order in which the parts removed from the thick wire link were removed in. This thick wire link is also attached to the main throttling bracket on its left hand side which is out of view.

Figure 9: Throttle shaft E disassembled parts

Figure 9 shows the disassembled parts from throttle E shaft in the order in which they were removed. This also shows the bottom of the carburetor, or its "feet".

Figure 10: Throttle E shaft

Figure 10 shows the shaft E for the throttle having more parts inside. They do not stop at part 6 as shown in figure 9. Also the shaft where the diaphragm link is attached to is also shown.

Figure 11

In figure 11 the "feet" (bottom) of the carburetor assembly is visible. Also, note that part 6 on the piece of paper has a direction, in and out, where "in" is going into the assembly.

Figure 12: Solenoid valve

Figure 12 shows the Anti-dieseling solenoid valve. This is the valve or long nut that has a wire at the tip. This also shows the link that goes from the electric choke to another shaft that goes to the carburetor's "body". This link looks like a thick metal wire.

Figure 13: Automatic choke link

Figure 13 shows the automatic (electric) choke link being disassembled. Note that there are also another two or three pieces still attached to the throttle shaft E, but we won't worry about these yet.

Figure 14: Parts disassembled from automatic choke link

Figure 14 shows the parts removed from the shaft that holds one end of the automatic choke link. These are also shown in the order in which they were removed.

Figure 15: Parts removed

Figure 15 shows the parts removed from the automatic choke and the other three pieces left behind on the throttle shaft E. These are also shown in the order in which they were removed.

Figure 16: Diaphragm link attachment

Figure 16 shows the diaphragm linkage on the carburetor. Note the short shaft on the linkage. The spring pictured in Figure 15 is attached through a hole to this short shaft coming out of the bracket.

Figure 17: Choke pull off

Figure 17 shows the choke pull off and the point where this one is attached to another link.

Figure 18: Diaphragm assembly

Figure 18 shows the bolts and diaphragm assembly corresponding to the diaphragm assembly.

Figure 19: Calibration mark

Figure 19 shows a small mark on my automatic choke. I did not put much attention to it at first, but I am now assuming this is the original position of the mark with respect to the line where the pen point is touching. I believe you are supposed to adjust this knob to either rich or lean fuel by loosening the bolts and then turning the knob. Note that here the bolts are already loose, which means that this mark could be off, but its a starting point.

Figure 20: Automatic choke, removed

Figure 20 shows the inside of the automatic choke once it is removed off the carburetor "body". If you've been reading "head", "body", and "feet" throughout the article, it refers to the three big parts remaining of the carburetor once everything else has been removed. I will show a picture later.

Figure 20-a: small beads

Figure 20-a shows small beads inside the automatic choke that were inside when I opened it. I don't know what they are or why they were inside, but I accidentally dropped them all to the floor. I was not planning on leaving them in there anyways.

Figure 21: Automatic choke link

Figure 21 shows the automatic choke link connected at the bottom of the remaining housing part for the automatic choke. I believe this link had only a pin through its eye when I took it off.

Figure 22: Choke pull off link

Figure 22 shows the link connecting the choke pull off and the automatic choke. Although it looks like a washer, I believe it only has a pin at the end of the automatic choke. Also note that the link from Figure 21 comes out of the hole to the right of the one shown in Figure 22, on the same bracket.

Figure 22-a: Automatic choke link

Figure 22-a shows the link connecting the automatic choke and the choke pull off.

Figure 23: Automatic choke holders

Figure 23 shows the three small brackets or holders holding the automatic choke in place so that its knob does not move to a more rich or more lean fuel. These should be installed concave down, as it reads on the paper.

Figure 24: Choke pull off

Figure 24 shows what is left of the choke pull off before disconnecting the vacuum line to remove the entire assembly.

Figure 25: Replaceable valve

Figure 25 shows the replaceable valve that comes in the carburetor kits. This is here to show the order of the parts.

Figure 25-a: Replaceable pump disassembled

Figure 25-a shows the disassembled pump from Figure 25.

Figure 26: Fuel bowl

Figure 26 shows the fuel bowl after the glass has been removed. There is a float inside. Also, on the same shaft where the float there is a short tube at the end, this can be easily misplaced.

Figure 26-a: Fuel bowl

Figure 26-a shows the float removed from the carburetor bowl. Also note that the small tube has been removed to exposing the shaft which is not serviceable. The small tube is in front of the float.

Figure 27: Automatic choke

Figure 27 shows the automatic choke coil.

Figure 28: Carburetor jets

Figure 28 shows the jets and other bolts from the carburetor. This will be useful when removing the jets.

Figure 29: Evaporator/temperature/pressure valve

Figure 29 shows the evaporator or temperature/pressure valve removed. In order to remove it the bolts shown had to be removed. Note that the order in which these were arranged on the floor is the order in which these go back into the valve. Do not disassemble the valve any further, I think there are no gaskets for it in the kit.

Figure 30: Fuel plugs

Fgure 30 shows the plugs underneath the fuel bowl. These are covering one fuel jet each.