Advice needed setting up Hitachi Carburetor


#1

I’m finishing up my carb rebuild for the Subaru justy. It went well but the secondary throttle opening angle has me confused.
The manual says the secondary throttle plate should start to open when the primary throttle is opened to .236 or 43 degrees.
Right now the secondary doesn’t start to open until the primary is almost 90 degrees.
The part called the adjust plate has a square hole so I can’t rotate it. But even if I could, the plate that makes contact with the secondary side can only open the secondary .01 inches.
I’m holding the throttle wide open in the first picture, and you can see part # 8859 is hardly touching the secondary plate.
I’m thinking if I bend the plate on the secondary side flat (the part on the right that is bent down), I could get it to open when it should.
So, if any of that makes sense, I’m just wondering if I’m on the right track.
This is my first carb rebuild so I wanted to ask before I go hammering on it.


#2

I’ve worked on a lot of Hitachi carbs back in the 80s (Subaru and Nissan) but can’t say that I remember ever laying hands on a Justy carburetor. My memory is VERY hazy on this so don’t take anything I say as the Gospel truth.

Have you tried checking throttle plate operation with the choke flap fully open and all choke linkage in its proper position for a fully opened choke flap. I seem to remember that having an effect on plate operation. The secondary should also be vacuum operated.

Not meaning to come across as a downer but Hitachi carburetors are pure unadulterated crap; especially the ones with cast iron throttle bodies.
There were tons of problems with Hitachi carbs back in the day.

A very few Subarus had Carter-Weber carbs and those worked very well.


#3

The choke linkage connects to the primary throttle valve for the fast idle setting, I believe I got that part set up right.
I wish I would have bought a weber carb instead of a rebuilt Hitachi, but I was trying to keep everything stock. Since I don’t think I can replace the duty solenoid in the Hitachi, I will probably eventually get the weber.
The secondary is also vacuum operated. I wonder if I bend the mechanical linkage if it would make the secondary open too far.


#4

Was there any alteration in the relative position of the secondary linkage? If not install the carburetor and start the engine. If it runs OK take it out on the road. It may be that the translation of the factory’s specs was less than perfect. I had an old Subaru shop manual that read like a third grader wrote it.


#5

Back in the day I put a Weber kit (plus cam, headers etc.) on my '81 Accord.
Great way to go if emissions tests aren’t strict.
I would just take it out and see how it drives.
If the secondary is opening late it will seem to flatten at wide open throttle as rpm’s climb.
If you’re satisfied with the performance I’d leave it alone.
Late secondary might up the mpg’s a little.


#6

No alterations as far as I can tell.
It’s never had much throttle response above 50mph but it’s only a 1.2 liter.
Maybe the secondary plate bent itself down over the last 27 years.
I don’t know much about carburetors, but I feel like the secondary should open more than .01" at full throttle. Then again, maybe the vacuum does most of the work.


#7

Is the vacuum diaphragm good? They age and crack.


#8

Do you know an old hand that might take a look at your carb? Nothing beats having it in my hands to figure out what’s going on.


#9

Without carb in hand I can’t tell you what the issue is.

If all else fails do as texases suggested; find an old timer to take a look at it. In spite of the frustration I think you will find that the cause is going to be something very simple that is being overlooked.

Maybe someone in a local old car club or a small performance shop that does dirt track racing. Those people will be familiar with carburetors.


#10

I think my main problem was the accelerator pump diaphragm was torn, and the fast idle setting was way off.
I was just thinking it might perform better if I got the secondary adjusted properly. Maybe I will just leave it alone for now and not risk making it worse.
I brought it to a couple shops and they didn’t want to touch the carburetor. I’m glad I finally tore into my self because it really wasn’t hard and I feel more in tune with my car now.
I really appreciate all the responses, this is a great community.


#11

The Subaru Justy is a rebadged Suzuki it seems and the secondary is controlled by vacuum. The primary linkage blocks the secondary from opening until the throttle is opened significantly.


#12

I should have mentioned it’s a 1989 justy. Subaru manufactured the Justy from 1984 to 1994, then it has sold rebadged versions of other vehicles under the Justy nameplate.
The carb rebuild only made a slight improvement. The fast idle is now working, but the idle climbs to 2000rpm as it warms up.
I’ve looked for vacuum leaks by spraying carb cleaner, but that’s my best guess for now.
Anyone know if fuel should spray in both venturies when the throttle is pressed? Right now only the primary is getting a squirt.


#13

Should be only the primary, I think.


#14

Thanks for all the help so far. I don’t think that I have a vacuum leak, but I noticed that idle improves when I create a vacuum leak.
I’m now thinking the mixture control solenoid in the carb is going bad. I get 120 ohms and the repair manual says to replace it if it’s over 100 ohms.
My current symptoms after the carb rebuild are occasional high idle when warm, and constant huge lack of power warm or cold.
Could this be the mixture control solenoid?

If so I’m ready to buy a weber carburetor.


#15

Feedback carbs are an abomination.
Webers are one of the best and highly tweakable.


#16

I’m thinking if it idles better when you create a vacuum leak it is running rich. Mixture control would be a likely place to start.


#17

Rechecked the timing today and it was way off. The last shop I had it to must have adjusted it with out connecting the plug under the dash. That’s why I didn’t think the carb rebuild helped.
Running great again after 5 months of replacing random parts.
Thanks for all the help.


#18

At least you got a bunch of new parts out of it and made some new friends. Congrats for solving the problem.


#19

Someone here one said ‘most carb problems are ignition problems’. Here’s another one.