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Hitachi Fail in 720


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#1 Humboldt

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Posted 09 May 2017 - 01:37 PM

My reliable 80 720 started misbehaving. It got to where I would have to rev it way up 7000 ish and slowly let the clutch out to limp it home two blocks. My son came over and (he has better eyesight than me) discovered a freaking 12mm nut in the bottom of the secondary chamber!!! Not the side with the choke on it. I have no idea how this bolt got in there. 

With the nut removed, the idle returned to normal (it was high) and it revved normal, so I decided to give it a test drive. Result: Fail. It still did the same thing and I had to push it home (1 block).

Full disclosure. When the truck was progressively losing power I blasted the carb (with motor running) with choke and carb cleaner.

I appreciate any help with this bizarre problem.

 



#2 datzenmike

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Posted 09 May 2017 - 07:46 PM

Primary jet likely clogged or at least party blocked. Engine will idle perfectly and rev reasonably well in neutral but any load and it falls on it's face.,


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#3 Humboldt

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Posted 09 May 2017 - 11:30 PM

Got the carb off and will pull the jets out. thinking of reaming with appropriate gauged guitar string if clogged. With the carb off I am tempted to rip all the pollution shit off and throw on a weber. I am 3 years into this vehicle. It was stolen from me and compensated for the radio that got ripped , with a liberal compensation by the insurance company--more than I paid for it. It was Oregon sourced, but like all things Humboldt, it's rusting as you look at it. The minute I commit to putting a Weber, it will be worthless for resale (it would never pass smog, which, once you own you don't have to do again here in Humboldt CA) so I would be gloriously commiting to my beloved work truck.

I think this truck would roar without the air pump and the reat of that shit. I have an intake manifold that has minimal smog shit. I,as many Ratsun devos, like the minimal approach. 

 

PS my 510 goon project is ugly but emminent. I just have to rip off the passenger door stuff to get the key codes off the lock cylinder to make an ignition key instead of holding my jaw right while fudging a weird key (some gas cap key or something) to get it to function. I also have fingers crossed the gas lines aren't fukked. I drained the 4 + year old amber puke colored gas from the tank.

 

Should I dump the shitty vibrator (ha ha Hitachi)? And weird 1980 pollution crap? No purist here--realist. One less Datsun to the junkyard! Thanks for advice and opinions!!



#4 datzenmike

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Posted 10 May 2017 - 05:07 AM

NEVER ream the jets out to clean them. Spray and blow them out.

 

There's nothing to stop you putting a Weber on and then putting the original one back on to sell it.

 

Just take the air pump belt off to disable it. Or take it off and save it for when you sell. You won't notice a thing though. There is no performance increase from removing what little pollution controls there are. Just keep the vacuum line to the distributor and pull the other lines off. Keep the PCV valve and hose operational.


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#5 racerx

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Posted 10 May 2017 - 12:16 PM

he lives in Calif. and don't think weber is smog legal.



#6 banzai510(hainz)

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Posted 10 May 2017 - 01:33 PM

I had a bolt or nut almost go down a carb also.

 

If you can drive the car when you first start it as the choke will be on and seems to run better than most likely the main jet is plugged. Ck your fuel filter if really bad or change that forst then re run your truck.

 

make sure the 2nd art plat on carb where you say that bolt was is fully closed and doent come open to soon (a spring maybe have fallen off tokeep it closed. It open under high vaccume


Throw on some Weber sidedrafts, Rising Sun hood.... call it good

#7 Humboldt

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Posted 10 May 2017 - 05:23 PM

Thank you all for your valuable information. I got the carb off , took out the jets and ran gutar string of slightly smaller gauge through them before I read Datsun Mike's post. They didn't seem hideously clogged. I also bent that little brass piece on the top of the float up so that it would actuate that plunger switch thingie sooner. Put it back together and so far, so good. If it craps out tomorrow I may thing that its the float getting saturated with gas and not floating. Or did they get that dialed in by 1980?

Lessons learned:

1. You have to take off the valve cover to get a wrench at the nuts on that side of the carburetor. (anyone have any tips on lessening the pain of getting at those four nuts?)

2. Don't work on car when you're sick or feeling shitty, it takes twice as long and you will do stupid stuff.

3. But do work on the car, or truck on one of the four days a year when the sun is shining in Northern Humbolt!

4. Those telescoping magnet things are great when some fumble fingered arthritic old bastard inevitably drops a screw or nut into a dark place.

Thanks again!



#8 datzenmike

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Posted 10 May 2017 - 06:43 PM

12mm wrench? Cut an open end down to about 3" long.


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#9 Humboldt

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Posted 10 May 2017 - 09:55 PM

Wait, sacrifice a perfectly good Harbor Freight wrench? lol. Just kidding, I will do that because I realize I forgot to put the heat shield on my Weber in the goon (CRS again), so I have to do the whole ritual again. Also, we have a 610 with similar issues.  Thanks again



#10 willz

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Posted 11 May 2017 - 01:08 AM

I took a wrench I had laying around, torched it to put a bend in it and shaved the sides of the wench down. Don't know where jt went or I'd take a picture. Went with a single side draft carb, love it and with ditching all the emissions stuff, made the bay look much nicer and easier to work in

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#11 Humboldt

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Posted 11 May 2017 - 06:31 PM

That's pretty cool looking. Weber side draft (which one? mm. jets?, manual choke?) Cannon Intake manifold? hard to find? Any issues? 



#12 willz

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Posted 11 May 2017 - 07:38 PM

Cannon manifold, 45dcoe (older Italian) manual choke. Tuning has been a breeze with this guy

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It was already set up for an L20b so I haven't taken it apart to look at the jet sizing yet

#13 willz

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Posted 11 May 2017 - 07:45 PM

I did have to buy the linkage and spring kit from pierce manifold to use it, well worth the money

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#14 willz

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Posted 11 May 2017 - 08:21 PM

But then again, my 620 isn't my daily driver and my wife lets me blow money on it.. which is nice since I've put more money and time into it then most sane people would...

I mean really.... how many guys on here are running a wideband sensor in their carb'd motor lol

#15 Humboldt

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Posted 11 May 2017 - 11:28 PM

Not sure what the wideband sensor is but the rest looks interesting



#16 willz

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Posted 11 May 2017 - 11:30 PM

Gives you a real time analysis/read out of your air to fuel ratio.

#17 Crashtd420

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Posted 12 May 2017 - 02:56 AM

I mean really.... how many guys on here are running a wideband sensor in their carb'd motor lol




Me.....

#18 willz

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Posted 12 May 2017 - 06:53 AM

Well I know you are, but I honestly can't think of anyone else. A lot of guys on here tune based off of spark plug colour, which works but isn't as accurate obviously. Plus the 32/36 Weber seems to be the popular choice, so the proper tuning on those has been done and the correct jets and settings already figured out for you. Same goes for the dual side drafts, theyve been done.

If you don't plan on selling it in the near future, I would suggest the Weber. You can find a used one for around $100-200. Keep the old stuff for when you're ready to sell it finally.

#19 Humboldt

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Posted 15 May 2017 - 04:52 PM

Hitachi Fail II. The Nightmare on My Street.
I got up this morning, having not driven the 620 for several days. To my utmost frustration it has started cutting out again! I just fueled up on Thursday with a full tank of Cali's finest ethanol laden premium gas, but I am wondering if there is crap in my tank. Do carburettors go intermittent? WTF?



#20 willz

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Posted 15 May 2017 - 05:03 PM

Buy a Weber. Easier to maintain and It'll be more than likely the easiest route if you plan on ditching your emissions crap. I've rebuilt a hitachi before, the resaulta were less than impressive