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carb swap?


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Hey there!  not sure if this is a dumb question or not but.... I just purchased a 83 720.  she will no longer idle, turns out the electric choke is dead.  cannot seem to find the electric choke part on the internet or in town (junk yards included).  So i am looking at replacing the carb.  is this a hard thing to swap out?  should i just try to rebuild the carb instead?


backround info, I am not a mechanic.  very little to no experience working on cars.  can do the oil and swap a fuel filter but thats the extent ha.  thanks for the help!

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There are no dumb questions. Well I suppose there are just a few but generally it's dumber not to ask.



It's far far easier to fix the choke than look for and install another carb. A carb that may simply be someone else's piece of junk, worn out, or rebuilt and missing pieces. At the very least you could install a manual choke cable and turn it on and off from inside the cab.


Lets see...


Electric chokes are not powered directly from the fuse box. Power has to come from a special choke relay that needs a good charging system to energize the coil and keep the contacts touching. This set up thus, only allows the choke to warm up, IF the engine is running. Usually on the 720 when the alternator is charging poorly or not at all, the relay (located up under the dash on the pass side kick panel) will make a light buzzing sound. If you have a poor charging system, maybe the red charge light flickers or comes on dimly then this is the problem. The alternator. I'm not suggesting that you run out and replace your alternator, only that it could be the problem.


Now, strictly speaking you don't have to have the choke powered by the choke relay. You can go around the choke relay by simply finding another power source that is switched on and off with the ignition. Well, right on the carb beside the Blue electric choke wire is a Red wire going to the idle cut solenoid. It is on any time the ignition is on and will do for this. Simply join the choke wire to it and the choke should start working.


Your carb won't be exactly like the one below. The large Black round thing is the choke heater and if you look closely the wire to it is actually Blue, but has a Black cover on it. The hexagonal thing to the right with the Red wire is the idle cut solenoid.





Last.... the choke heater is actually burned out or inoperative. (very unlikely but possible) Just get another from a spare carb, or a manual cable and convert it.


This is the choke heater. You can see the heating coil in the back. It warms the bi-metallic coil and it unwinds and turns the choke off. When it cools it contracts and sets the choke on for the next cold start.



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wow thank you so much!


when i was diagnosing the problem with my mechanic, he applied power to the choke and it still did not work.  so even if i found an alternative power source for the choke i do not believe that it would work... please correct me if i am wrong. 


I will definatly check the alternator to see if that is giving me any trouble.  that atleast is a cheaper part than a carburetor ha


im making the trip out to where she is parked now to check on those couple things. ill give an update tonight.  thank you thank you mike

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First make sure the choke is not jammed from sitting. The heater may still work but it won't open. Takes about 5-8 min to fully open when on.  Hold the throttle part open and close the choke plate...










It should be free to move.



Next, remove the three hold down screws on the choke heater and make sure the J shaped part on the coil is wrapped around the horizontal rod to the choke flap. If someone had it off and didn't put it on right it won't move.




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so did some recon.  i believe the choke is jammed. here it is closed:




Here it is open




so i guess thats where i should start. also when i reroute the electric from the choke to the idle cut solenoid, am i supposed to splice the wires? here is what i am working with




when i go to reroute the wire, from my understanding, i take the bottom end of the blue wire and connect it to the right hand side of the red wire?


i also checked out the alternator and it seems like mine is pretty new.  i also could not find the red light that indicates the alternators status. i was looking under the glove box on the passangers side... i might have misinterpretid mike's instructions. but here is a picture of the alternator from the passanger side front wheel. like i said it seems to be pretty new.




going to try to do some more work tomorrow

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I would just trim the insulation from the Red solenoid wire for about 1/2". Cut the Blue wire far enough from the choke heater that it will reach the Bare Red wire. Bare the Blue wire and wrap around the bare Red wire and solder in place. Insulate with electrical tape.


If the choke is jammed it needs to be loosened.

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