Stock L16 Hitachi carb rebuild + tuneup questions

[ratatat dat]

Hello all!

 

Car: 72 wagon.

 

Doing an OEM carburetor rebuild and have a lot of questions… it's my first rebuild. If you can help, I would be very grateful!!!!

 

1. What is this? What does it do? Should I tap it apart with a hammer and clean it? I haven't seen one on many other 510 carbs............

 

2. Are these fully ready for the ultrasonic cleaner?

 

I can't tell if this black sleeve/walls inside the main throat need to come out or not:

Underside:

 

It seems there is no way to remove that upright spring. Is it okay to put in the solvent like this?

 

Last part:

 

3. This is an old rebuild kit. When rebuilding, do gaskets just go in dry? Are you supposed to prep them in any way? Noob question, I know.

 

4. The kit gave me a new one of these. Mine looks really clean and functional but should I replace it anyway?

 

5. What is this? What does it do? Obviously I won't put it in the solvent...

 

If I can get some help and figure this process out, I might try to make a picture-heavy guide and post it here. Here are some pics from before I took mine apart.

 

Can't tell if this is rubber or metal in that hole... it seems hard but I am a little scared to put it in solvent. Anyone?

 

 

 

TYSM!

 

 

 

[datzenmike]

 

 

 

This is the BCDD (boost controlled deceleration device) It's a tiny carburetor inside the carburetor supplying extra air and fuel during high speed deceleration when extreme intake vacuum causes an over lean condition that does not burn completely and produces high levels of hydro carbons in the exhaust. Under certain vacuum conditions the BCDD opens and allow extra air and fuel in until the manifold vacuum decreases below a threshold as the engine speed lowers. If the engine tends to have an unexplained 'fast idle' the DCDD is set too sensitive and does not shut off properly. Turning that adjustment screw counter clockwise decreases the threshold sensitivity that turns it on. For the most part it's problem free. I wouldn't submerge it in cleaning fluid and clean separately.

 

 

The venturies are removable but California carburetors are not. I would leave them alone.

 

 

This is just a plunger that is pulled down by intake vacuum. Under heavy load with secondary open this plunger allows the power valve to open, adding enrichment for maximum performance. It's fine to leave in. Below is where the power valve is located. I don't expect the kit provides a replacement...

 

 

 

Absolutely gaskets go on dry just like when the factory put them together. Sealer is redundant and basically glues the carburetor together. RTV is for GM owners that have poorly fitting parts that need to be sealed.

 

 

Most definitely use the new one provided and any new washers. Inside is a needle valve that wears and if it does not seal the float chamber will over fill and flood. Keep the old one as a spare. Just inside the 'banjo fitting' you removed to get this part out is a tiny brass screen. Later ones are thin mesh plastic. Make sure it is cleaned and put back in

 

 

 

This is the vacuum diaphragm that pulls the secondary open. Dont't use solvent on it. There should be a BB and a small spring under that small hole beside the screw hole. Don't loose it!

 

Speaking of losing things. In the picture below, on the end of the hinge pin the float swings on, is a very small brass piece. Don't loose this as it keeps the hinge spaced away from the glass window.

 

 

 

 

 

 

 

 

 

[ratatat dat]

Dude, thank you so much...

All that is so helpful.

 

So the BCDD is basically an emissions thing - makes sense for '72. I won't put it in solvent. I assume tap it apart w/ hammer and shoot it w/ carb cleaner?

 

This is a Cali car. By venturi do you mean the black walls in the main throat? I'm not actually sure what that word means. Either way I will immerse the main body of the carburetor as is.

 

This is how the banjo fitting came off. I never saw any mesh. This is not the first time this carb has been rebuilt. But first time by me.... am I missing that?

 

Re: vaccuum diaphragm... I never saw a BB/spring there and it appears that small hole next to the screw hole is empty. Maybe the last person lost it? A local junkyard has one of these carbs so maybe I'll buy it and see if that one has the BB/spring...

 

 

 

[datzenmike]

It's for reducing emissions but only works when slowing down so has no effect on performance or anything else. There is less popping and rumbling in the exhaust. I would just clean the outside.

 

Yeah the black things in the barrel. Just soak in carburetor cleaner and brush clean.

 

The mesh screen goes over this part...

 

 

and the banjo fitting over it. If you get the carburetor get than part also.

[yenpit]

I can't help with rebuilding details, but if you need any parts, I have quite a few of these 510 Hitachi carbs, parts & some NOS parts!  Pm if you need anything!

[ratatat dat]

Hey all,

Back with a couple more questions. As my first carb rebuild it has been a confusing but very intriguing process.

 

Re: Mike when you were telling me about the power valve, you are referring to that plated screw thing underneath the plunger in this pic, right?

 

 

Next, as you can see, it looks like the BCDD has a tiny mesh covered opening on the front - which appears clogged. I would shoot carb cleaner in there, but right behind it there seems to be a rubber diaphragm... that diaphragm isn't replaceable, right? Do you agree I need to figure out a way to clean that mesh?

 

 

 

 

 

Lastly for now, this is just a spacer right? Am I looking at a hard plastic with a gasket on either side? Do I need to replace those gaskets by making them? The rebuild kit did not come with these. Thank you so much and sorry for the noob questions...

 

 

[ratatat dat]

What is your preferred way to clean the jets and main body?

 

I tried ultrasonic cleaner with hot, soapy water, (then dry off with compressed air) and it did something, but still nothing is exactly all one color.

 

But according to a local mechanic he always used to dip them in solvent and pretty much let it sit for 30m. But according to him the quality of solvents has gone down, esp. in California. Lol

 

Someone online recommended soda blasting which looks like it requires a cabinet. Anyone ever tried it?

[datzenmike]

 

Yes power valve is under that spring plunger.

 

 

 

While on that picture there are 4? philips screws on the underside of the carburetor base. A short one on each side, and two long ones at front and back. The very front one is HOLLOW! and allows a vacuum signal up through the carburetor to the top to pull up on the spring plunger and open the power valve. They are often put back in the wrong location when rebuilding, making the power valve inoperative. Wouldn't you know it? the carburetor I pulled out of my junk pile for pictures was wrong, so someone had it apart in the past.

 

Under certain heavy throttle conditions, for best power, the mixture needs to be richer than the main jets are set for. The job of the power valve is to allow more fuel in.

 

 

 

Also why there is a half circle gap in the gasket over that screw. Make sure it is unobstructed. Some plastic spacers are notched into the secondary for vacuum.

 

The main jets just have to be clear. Run a tooth pick through them is good enough.

 

BCDD is only critical when it fails to turn off after slowing down. I would leave it alone or clean with a toothbrush.

[ratatat dat]

Dude, where did you learn all this?

So helpful, I really appreciate it.

I hope to make a guide for other noobs once I get the hang of this!

[datzenmike]

Trial and error, which is a nice way to say: by making a lot of mistakes.

[ratatat dat]

Hi again,

 

Put the carb on finally and tried starting.

 

I put a bit of carb cleaner down the throat and it sputtered for a bit, pulling fuel into the float bowl.

 

However, all the fuel fell right out from beneath the glass window. See the little droplet underneath the bottom screw? And the intake manifold is wet.

 

Upon rebuilding the carb I did NOT use the new black rubber window gasket, because it was too hard to get in. I also didn't want to tighten the window screws too much because the instruction sheet said not to.

 

Anyway, I tightened the screws more and it still leaked all of the fuel right out.

 

I guess I will try to put the new rubber gasket in. But does anyone have any tricks for that?

Basically you are trying to fit the rubber strip into a channel and - if you have two sets of hands, you can get all 4 corners in, but how do you put the glass on after? As soon as you take a finger off, the rubber pops out...

 

So looking forward to driving again!!!!!

And it's really nice to look at a slightly cleaner carb!

 

 

[yenpit]

13 hours ago, ratatat dat said:

Hi again,

 

Put the carb on finally and tried starting.

 

I put a bit of carb cleaner down the throat and it sputtered for a bit, pulling fuel into the float bowl.

 

However, all the fuel fell right out from beneath the glass window. See the little droplet underneath the bottom screw? And the intake manifold is wet.

 

Upon rebuilding the carb I did NOT use the new black rubber window gasket, because it was too hard to get in. I also didn't want to tighten the window screws too much because the instruction sheet said not to.

 

Anyway, I tightened the screws more and it still leaked all of the fuel right out.

 

I guess I will try to put the new rubber gasket in. But does anyone have any tricks for that?

Basically you are trying to fit the rubber strip into a channel and - if you have two sets of hands, you can get all 4 corners in, but how do you put the glass on after? As soon as you take a finger off, the rubber pops out...

 

So looking forward to driving again!!!!!

And it's really nice to look at a slightly cleaner carb!

 

 

 

Give it your best try, if you can't get the rubber seal to work, PM me............I might have an NOS rubber seal.  I have plenty of parts carbs thus glass windows, so I can test fit before wasting time on a shrunken seal!

 

TJ

[datzenmike]

The rubber is roughly rectangular and should stay in position. It is square edged and fits the square groove for it. Make sure it is spotless, use carburetor cleaner and a rag. If there is any crap on it or the groove it will leak. I've taken dozens apart and cleaned and reused and they never leaked. You can do this.

[ratatat dat]

Thank you guys, yenpit I really appreciate the offer. I will probably need a couple parts for my next rebuild at which time I will PM you!!

[ratatat dat]

New window seal gasket in!

Carb installed!

 

Sprayed carb cleaner down throat to help it start, and...

 

 

Few things:

 

Once the carb cleaner has been burned, it will NOT run on gas, unless choked!

 

So I choked it and ran for 2-3 minutes.

 

Even after warming up, it dies as soon as I let off the choke.

 

Choked and running, it also dies if I try to rev it with the throttle linkage.

 

However, if I artificially open the secondary valve by hand, it stays on and revs.

 

-

 

 

The engine dying when I open the throttle was the exact issue I was having before I took the carb apart. I guess cleaning everything was redundant but at least VERY educational.

 

-

 

Some facts:

 

The float bowl is not full, while playing around I only got it to about half level at most.

See:

 

 

The idle adjusting needle is 1 3/4 turns out from lightly seated, as suggested by the rebuild kit.

What does this needle do???

Is IN leaner and OUT richer?

It's SUPER touchy, right?

My car never had a problem before this was touched by some friends.

 

 

What is that other screw that holds the main throttle valve ajar? I have it so it's NOT doing that. What is the point of that anyway? If you want a 1500 RPM idle?

 

 

 

 

Thank you! I am so looking forward to driving again...

[ratatat dat]

This is not my EXACT carb, but here's this...

 

 

 

EDIT sorry that's blurry. I'll scan it and upload a better one for others sometime.

[datzenmike]

19 minutes ago, ratatat dat said:

Sprayed carb cleaner down throat to help it start, and...

 

 

Few things:

 

Once the carb cleaner has been burned, it will NOT run on gas, unless choked!

 

So I choked it and ran for 2-3 minutes.

 

Even after warming up, it dies as soon as I let off the choke.

 

Choked and running, it also dies if I try to rev it with the throttle linkage.

 

However, if I artificially open the secondary valve by hand, it stays on and revs.

 

Runs on secondary but not on primary: Primary jet is plugged or fuel not getting to venturi. The primary jet is on the left under a hex shaped plug directly below the float chamber the secondary is just to the right of the primary as viewed from the front.

 

 

 

19 minutes ago, ratatat dat said:

 

Some facts:

 

The float bowl is not full, while playing around I only got it to about half level at most.

See:

 

 

Float should be up and horizontal when float chamber is full. Bend tab on top downward to raise the fuel level.

 

 

19 minutes ago, ratatat dat said:

The idle adjusting needle is 1 3/4 turns out from lightly seated, as suggested by the rebuild kit.

What does this needle do???

Is IN leaner and OUT richer?

It's SUPER touchy, right?

My car never had a problem before this was touched by some friends.

 

In is lean and out is richer.

Should not be 'touchy'. Should have as much as a full turn without noticeable effect between too lean and too rick.

If turned in too tightly the needle valve can be damaged. Remove and have a look at it.

 

 

 

 

19 minutes ago, ratatat dat said:

 

 

What is that other screw that holds the main throttle valve ajar? I have it so it's NOT doing that. What is the point of that anyway? If you want a 1500 RPM idle?

 

 

The screw on the left is the idle adjustment screw and it holds the throttle open enough for proper idle. If loosened enough the throttle will close and the engine won't run. Idle speed is set with the engine warmed up (choke and fast idle off)