anyone know of a good 720 carburator service manual? z24 engine

[nissan/datsan720]

Want to rebuild my carb and would like somehing to reference... Any one know of any good service manuals for the carb alone?

[nissan/datsan720]

Also.. Anyone able to tell me off the hat what this could be... High idle.. When i fingerpress the accelerating Pump lever im gettn things back to low and steady idle... Jets are workin. In access as well.. Burning really rich and also from visual inspection.. Fast idle Cam seems to be ok... Any suggestions... Hah i know it could be a handfull.. Feel free to ask more ... Been stuck on this one for a bit now...

[nissan/datsan720]

Will add more later too... Just cant think of the other things at the moment

[datzenmike]

Fast idle causes...

 

Linkages dirty and sticking. Hose down liberally with carb cleaner while moving all linkages by hand. Hold throttle 1/2 open while closing and opening choke by hand while doing this. (most likely cause)

 

Fast idle screw needs adjusting.

 

Alternator not charging properly. Causes auto choke relay to not work. Relay needs a charging alternator to provide choke heater with power. Without power choke does not fully heat up and only warms up from engine heat and choke is part on.

 

Throttle shaft worn oval. Hangs up when released.

 

Throttle cable too tight holding throttle open. Just adjust.

 

Secondary not fully closed.

 

BCDD adjusted too sensitive... doesn't shut off. (turn counter clockwise to reduce)

 

 

 

A factory service manual for your year has good description and drawings to show operation and adjustments. Rebuilding (to me anyway) has always been successfully cleaning and re-assembling them. Not much to wear out but the accelerator pump and the throttle shaft. Dirt is the biggest problem for the very sensitive small orifices and air bleeds.

 

Have a large clear table covered with newspaper and a camera to take pictures for putting back together. Philips screwdriver, 12mm wrench, needle nose pliers and a flat blade screwdriver with the sides ground down so it fits up into narrow places to remove jets. Carb cleaner and a roll of paper towels, A dental pick and an old tooth brush is good also.

 

A good quality re-build kit will have instructions for settings and really it just goes back together they way it came apart. Take pictures.

 

Hint: one of the base to main body screws is hollow. Don't put it back in the wrong hole. This is the vacuum signal for the power valve. The accelerator pump has two BBs as one way valves. Don't let them get away.

[nissan/datsan720]

Got a service manual... Im slowly checkn on things and adjusting when needed.. Not puttn a whole lotta miles on it anyway. For now(i tend not to drive much anyway) but who knows if thatll change when its fixed?) was hopin on somethin a little more specific for the carb itself... (i like to have things visualized a bit better before i open them up.. And since im new to carbs... Was hoping id find somethin a bit more detailed than the service manual since it focuses on every part and not specifically the carb... Which is somehow squeezed into a few small sections... (basically its written well for someone who has already serviced carbs and is good as a reference... But curious if theres anything more detailed and descriptive than the factory service manual for the whole truck... I am doin the rebuild with a friend who has more carb exp than i but would like to learn more about them too.. And if it wasnt clear yet... I really just want to read it also

[nissan/datsan720]

Also thank you... And hey.. Do you know what carb kit i would get for an '85 720 2.4... Are there diff carbs for diff years?.. Say 84 and 85? Cause mine has a swap engine from an 84..

[LenRobertson]

One thing I can think of that you may find more useful than the FSM is the book  "How to Keep Your Datsun Nissan Alive*. The section on carbs is pretty step-by-step on what to do. Unfortunately it is getting to be a scare book and rather pricey. I think I saw somewhere it has been scanned and is online, but I don't have a link. It only covers L-series Datsuns so your carb may be enough different that some of the info won't apply for you. Warning: the book doesn't have pretty pictures, only very understandable drawings.

 

I just did a search on eBay and AbeBooks. Yikes! $77 on eBay and over $100 on the online book dealers. You should  try to find an online version to see what you are getting before spending that kind of money.

 

You should  get a kit for the year of your carb so the exploded drawing in the instructions is close to what you have. Some kits have kind of generic Hitachi carb drawings so you can't absolutely rely on them.

 

I don't know if your newer carb has them but on the '70s Hitachis there are two tiny steel balls for the accelerator pump circuit that are easy to lose when tearing down if you aren't watching for them. One is under the accel pump itself and the other is under a brass plug on the main carb body after you remove the carb top. If they get away you will never see them again. Some carb kits include new balls - but only if you don't need them. If you lose one or both balls from your carb you can be sure your carb kit won't have them. :D

 

Len

[datzenmike]

This is why you should have a camera. Take lots of pictures. Not much wears out on a carb. It comes apart and it goes together, just take your time. The most important thing is cleaning. This it the biggest reason why a carb acts up.  

[nissan/datsan720]

Yeah thinkn ima just have to set a good day for the rebuild... Leaving plenty of time kinda deal... Usually when i get a super clear diagrahm it cuts the time in Half... But ima just have to rough it.... Also lookin at the diagrahm ive got in my service manual. It seems to only have one of those bearings in this years model... Ill keep an eye out for an extra and set a tarp or sheet down to catch any runaway

[nissan/datsan720]

Ok... So its startin to look like i will need a new carb soon enough.. Unless we can get these damn seized bolts off without havin to drill.. As a temp fix ive been pullin the carb and adjusting what i can to get it running smoothly.. But theres a bunch of red coming out when i flush it... Last week one of those chunks of rust clogged one of my jets while i was out in the sticks... Had to keep tap pumpin and popping into neutral on the highway goin ninety mph... Well i guess the ninety wasnt a had to.. Just got a leadfoot... But yeah.. Thinkn ill eventually get a weber.. ... Will i have to change the ecu settings for this. I also heard of people ditching the ecu after installing one... Is this just hyped up bullshit or is the ecu actually only fuctioning as a carb control? Damn was hopin to save up for a ka swap... But will need to do this soon anyway.. And a carb most likely wont be near the price of the swap anyway... Well turns out though.. These things are super addictive..lol

[datzenmike]

Replace the fuel filter. It's job is to catch any rust flakes and dirt from the tank. I've had cheap filter elements fall apart inside the filter case. Get a net filter on and get the carb cleaned out and it should stay clean.

 

There should be a super fine mesh screen right at the fuel inlet (banjo fitting) to the carb. If someone had it apart it may have been left off, or it might be torn and letting crap through.

[nissan/datsan720]

K thanks for the heads up.. I changed the fuel filter not so long ago.. In terms of milage... Ima check this banjo fitting.. Considering that im not sure this carb was ever opened... All bolts ive tried so far are seized im thinkin it could be some rust on parts of the float or possibly the jet thats clogging ... The airfuel ratio cylnoid sounds a bit louder than i think it should too gotta get it open before all this shit goes... Ima see if i can reverse bit any of the bolts when i get a chance.. But yeah a new weber is lookin pretty nice at this point.. Got it tuned enough to get back to the inspection shop just waitn on this switch to come in... And hopin the only problem with my horn is in the combo switch

[datzenmike]

The feedback carb is problematic. The connector at the back is on wires that are too short and this forces them to bend and twist and they can break or make poor contact. The ECU under the driver's seat needs several inputs from the carb in order to determine the mixture setting. Next time it's running wiggle them and see if it changes the idle.

 

O₂ sensor..... they don't last forever. If there is a failure in the feedback system the ECU reverts to a 'limp home' mode of over rich mixture so the engine is not damaged by a mistaken lean mixture. Performance and mileage are severely affected.

[living_4kicks]

I rebuilt mine. Ran better than before, but still had problems with idle, burning rich, and delay acceleration. So I put on a weber. Runs better than new and is simple to do. Took less than a hour to do. Just a idea

[racerx]

Nissan/datsan 720, check manuals on general discussion. Forgot his name but he downloaded tons of manuals.

[nissan/datsan720]

Oh hey.. Forgot i hadnt updated this yet.. Well still not done yet.. Been drivin my cab non stop till this past two days . god damn i needed a break... Gettn back in my 720 felt crazy for a minute hah.. But yeah... Update.. The Phillip s head bolts on the hitachi are seized.. .. Between shifts at one point it was a nice enough day so i started taking it apart.. Only to find out that most of the bolts are seized.... And there is looze rust that has been randomly clogging different parts... No shit it was goin crazy... The jets are clogging at random times and im sure theres a leak in the gasket in the middle somewhere.. The base gasket change made a huge enough difference alone... But have had to pull it off and on a few times to keep trying to flush it(since i cant get it open) it was acting up again today just as i was ony way to get my inspection sticker... I swear... Lil niss.. knows when i need to get somewhere hah.. Anyway... Lucky.. for me i already passed my smog a few weeks back and was just goin back after fixing some light shit for the inspection sticker... But yeah.... At this point im buyin a weber... Also anyone have experience switching to power steering from non

[Cannabinoidgenes]

Here's a question. I'm thinkin about going the other route and just getting a remanufactured carb. They sell them at o rielly can anyone attest to their quality/ does anyone know of a good seller or rebuilt carbs.

[datzenmike]

Probably Chinese knockoffs.

 

 

There isn't much in a carb to wear out. The biggest problem is water and dirt getting in. Dirt gets in every time you gas up, it's unavoidable, so keep your fuel filter changed at least every 3 years oftener is fine. If you have a dirty tank maybe some rust? and don't change the filter it will just do the same. Get a good filter. I had a cheap one just fall apart in the plastic body... you could see it rattling around when shaken. Naturally all the shit ended up plugging the plastic screen at the inlet needle. Would have saved me an hour to have spent $5 and changed it. before this happened.

 

I haven't used a rebuild kit since the '70s. I disassemble carefully and clean everything. Gaskets don't wear out and the only gasket on a Hitachi that keeps gas in, is the one on the front of the float chamber. The accelerator pump does wear out and in extreme cases the throttle shaft can wear the carb body. Carbs are like Swiss watches. Very small holes orifices air bleeds and jets that are easily plugged.