720 Carburetor Tutorial with Pictures

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
Corradokid90
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Re: 720 Carburetor Tutorial with Pictures

Postby Corradokid90 » Thu Aug 27, 2015 3:15 pm

fastboatman29212 wrote:Pics won't tell me much because I won't be able to see how the linkages work. Sounds like you are right. Probably the secondary is not working.
Dumb question... Is the secondary on these carbs linkage activated or vacuum? I also couldn't help but notice there's no dashpot on the carb but there's a bracket for it. Sorry to flood this thread with my lack of understanding haha


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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Thu Aug 27, 2015 6:36 pm

The carb should still work OK without the dashpot. I really don't know if the secondary is vacuum or not. Sorry.

Bobrclay
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Re: 720 Carburetor Tutorial with Pictures

Postby Bobrclay » Mon Sep 28, 2015 8:22 am

Guys, great photos and very helpful. I'm experiencing fuel leak around accelerator boot on my 83 Nissan 720 Z24 Carb thought I might run this question up the flag pole and test the water.

I know I'll probably have to order a complete kit to get the parts but my question is can I replace the associated components without doing a complete removal or should I do the right thing and do a complete rebuild. Truck in one owner with 350k+ miles and only engine repair - head gasket.

I think I know the answer but wanted second opinion. Thanks and by the way great forum!

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Mon Sep 28, 2015 8:25 am

I'd try just doing the accelerator pump. I rebuilt my carb and didn't notice a big difference in performance. It did give me peace of mind.

NOT 420 JUST 720
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Re: 720 Carburetor Tutorial with Pictures

Postby NOT 420 JUST 720 » Thu Dec 24, 2015 1:04 am

I have an 85 kc 2wd, when shifting gears, the rpms stays at 2000 with the clutch in and slowly goes down. I feels like it's sticks. Any ideas?

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Fri Dec 25, 2015 10:13 pm

Well, could be a sticky throttle cable, vacuum leak, carb linkage is sticky. If it does that in the driveway, then I'd start with the throttle cable, then check for a vacuum leak.

NOT 420 JUST 720
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Re: 720 Carburetor Tutorial with Pictures

Postby NOT 420 JUST 720 » Wed Dec 30, 2015 8:06 am

thank you . Also on the freeway going about 65 mph, I push the clutch in and it revs to about 3000 and slowly goes back down.

NOT 420 JUST 720
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Re: 720 Carburetor Tutorial with Pictures

Postby NOT 420 JUST 720 » Tue Jan 05, 2016 10:11 pm

It was the cable. Time to replace it. For now I sprayed it with lithium white grease and runs great. Thank you bro.

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hi-tek-red-nek
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Re: 720 Carburetor Tutorial with Pictures

Postby hi-tek-red-nek » Sun Jan 31, 2016 8:15 pm

hey fastboatman, first off, excellent tutorial! I, like others registered just to comment. I ended up learning a ton of valuable info. My question is this. Background, I have two 720 4x4s my donor is low miles-ish (158000 ). My driver has high miles 300. I runs strong is stock (drivetrain). I want to switch out my hitachi for the weber on my donor. Also, the donor is beat to death and body rotting. I have plenty of experience swapping engines. Time is my issue. what is your opinion? And, off topic, soon as I can I will be letting parts go. If people have needs, well, a closed mouth don't get fed! Speak up and I'll see what I can do to help. P.S. great forum all around! glad I joined!!! Thank You, J.

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Sun Jan 31, 2016 8:26 pm

I've never done the Weber carb swap. People who did that swap like it. Just make sure all the vacuum lines get plugged. A vacuum leak will kill the performance. If U can do an engine swap on a 4X4 then you need to post a DIY if you have time because it would help others.

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Tue Feb 23, 2016 10:37 am

Hi my 86 z24 is flooding so bad that it won't start.. I'm getting spark and fuel and when I went to pull a plug to check compression there was a ton of fuel. What could be causing this the float being stuck??

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Tue Feb 23, 2016 10:39 am

Yes, the float is probably stuck. At least that's the first thing to check.

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Tue Feb 23, 2016 11:11 am

How would I tear it down to the float? Or is there a way to check it without taking it apart. I just get thrown off by your pics because mine looks different..

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Tue Feb 23, 2016 11:19 am

I'm the one who posted about the truck not even running on ether. It's driving me nuts cause we messed with it some when I bought it and drove it onto the trailer!!

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Tue Feb 23, 2016 11:25 am

Check out the DIY section. I made a carb rebuild DIY post. Study that post and you will see how to open and inspect the fuel bowl. Here is the link.
z24-carb-rebuild-diy-1984-86-t537596.html

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Tue Feb 23, 2016 5:53 pm

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Okay so I made it this far and haven't found that dang float.. sorry if I sound retarded I'm a lineman not a mechanic :rotfl

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Tue Feb 23, 2016 6:06 pm

Looks like your carb isn't typical for a 1984-86 720. Next step is find the place where the fuel line goes into the carb. That should be the fuel bowl. Make sense? Fuel gets pumped into the bowl and then the float rises. When the float gets high enough it pushes the float needle up to close the bowl inlet so no more fuel enters the bowl. Fuel then is diverted via other passages to the fuel return line where it goes back to the tank. Older vehicles like my 1965 Chevy truck have a lower pressure fuel pump and the carb float needle just closes.

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Wed Feb 24, 2016 2:00 pm

Put a new carb on it same results... Really gettin frustrated with this project!!

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Wed Feb 24, 2016 6:42 pm

I'm sure you checked the intake side for spark, but that has to be the problem. You have fuel. You have compression because it did run once at least. Either something is shorting out your spark or your coil is bad or intermittent. You can swap the intake and exhaust coils just to check. Not sure what else to say.

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waynosworld
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Re: 720 Carburetor Tutorial with Pictures

Postby waynosworld » Fri Feb 26, 2016 9:51 pm

That looks like the 1986 throttle body injection, it's not really a carb, I don't even know if it has a float.

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Sat Feb 27, 2016 10:52 am

How would I check the coils? I swapped the plugs on em n still no luck.. Hate to spend $70 on new ones to find out that's not the issue

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Sat Feb 27, 2016 10:58 am

Put spark plug and coil wires back the way it was when you first had it running. Pull a plug wire off if an intake spark plug but leave the plug in the head. Use an extra spark plug (or just buy an extra one) and hook it to the spare spark plug. Crank the engine while holding the plug next to a ground (engine block, frame, etc). You should see it spark while cranking the engine. If not, then the coil isn't sending a spark.

okieguy
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Re: 720 Carburetor Tutorial with Pictures

Postby okieguy » Tue Mar 01, 2016 3:56 pm

Ya I'm sparkin on both sides and the plugs are soaked n gas

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Tue Mar 01, 2016 6:11 pm

I'm out of ideas. Sorry.

BranS
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Re: 720 Carburetor Tutorial with Pictures

Postby BranS » Sat Apr 23, 2016 6:06 pm

:tisk: so I now found another broken piece on my carb..... choke control diaphragm? Driver side,short vacuum line going to top of carb? The arm on the diaphragm is broken.
First problem is broken vent...someone had messed this thing up.
I'm thinking may just need to get a carb. I'm in Cali so guess a weber is out. Anyone have any experience with any of the cheaper carbs out there? Probably not a good thing to cheap out on but if anyone has experience with them I'd like to hear about it.
Maybe it could be repaired. I think I'd send it in, I don't really trust myself with somthing so delicate. And getting it repaired right ...
Much respect Fastboatman.....

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Sat Apr 23, 2016 7:03 pm

My truck isn't running well. I seem to have low compression in at least one cylinder. My rebuilt carb may be up for sale. However, it's not a Cali carb. These carbs often get tossed and new purchased when parts break. Too bad about your broken carb.

BranS
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Re: 720 Carburetor Tutorial with Pictures

Postby BranS » Sun Apr 24, 2016 4:21 pm

Do you know where the ID tags at? How much you want for your carb fastboatman?

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fastboatman29212
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Re: 720 Carburetor Tutorial with Pictures

Postby fastboatman29212 » Sun Apr 24, 2016 4:26 pm

Nothing is for sale just yet. Sorry. I have to test compression first. If my compression is good then I might not sell anything. If the engine is shot then I will part out the engine, carb and sell the tires and wheels and then let someone make a rat rod out of it. Body and bed are in good shape.
I'll let you know in about a week.

BranS
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Re: 720 Carburetor Tutorial with Pictures

Postby BranS » Sun Apr 24, 2016 4:39 pm

Ok. Good luck. How many miles you got? Really can't belive this thing is being such a pain..... I keep doing stuff that's not helping dang it....

RavenS13
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Re: 720 Carburetor Tutorial with Pictures

Postby RavenS13 » Thu Jun 16, 2016 2:18 pm

astro800 wrote:I have 84 4×4 carb is making clicking noise and it won't hold idle. I changed both relays not sure what's up with it. I just bought it for 2500 and it won't run. I need some help thanks
I can't see that this question was ever addressed anywhere, however this exact thing happened to me today.

Got my new rear window installed and was driving the truck up the driveway from my shop and it sputtered a couple times then died. Would not re-start. Tried to fire once or twice but died immediately. When I popped the hood to check a few things there was a very loud ticking/clicking in the area of the carb. Towed the truck back down to the shop but it fired up and ran and the ticking in gone at the carb. It's been fine since so I haven't been able to diagnose.

Could that potentially have been caused by the anti-dieseling solenoid? Does it have any control over the fuel pump?

The air cutoffs on these are vacuum operated right?

Pretty stumped but it has me worried to set out down the road in this thing now.


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