Emiko, my new 520 work truck

[datzenmike]

On the Hitachi there are two smaller length screws on each side and two longer screws one at the front and one at the rear holding the base to the body. The two longer ones are identical but for the hole drilled through the length of the front one. This allows a vacuum signal from the under side of the carburetor up to the power valve (#60) this allows extra gas in under high speed full throttle to richen the mixture. It's easy to miss this and put it in the rear position disabling the power valve.

 

I don't know if this is the case here with this carburetor but have a look.

 

See through hollow screw...

 

 

[hucklefish]

Does anybody have a picture of the linkages on the back and sides of a J13 Nikki carburetor? My throttle and choke cables aren't connected correctly, though they sort of work. The way the throttle return spring was installed interfered with its own linkage. I moved one end and now the throttle returns to idle a lot more reliably, but it's still not right. I seem to be missing at least the "throttle wire holder" part 26: https://www.carpartsmanual.com/datsun/pickup-1965-1972/engine-1300-(j13)/carburetor/exc-ltu-(from-may-68)

 

This might be a little overkill... but here are a couple pictures of the carburetor with notes showing how I changed the throttle return spring and what else I think is still wrong (EDIT for clarity - this first picture is from after I removed and replaced the carb while replacing engine gaskets, and the other two pictures with the white zip tie on the throttle cable are from before the removal):

 

 

[hucklefish]

40 minutes ago, datzenmike said:

I don't know if this is the case here with this carburetor but have a look.

Yep, that's probably it. I somehow forgot to mention it did have a hole through it, and it was toward the front - actually I don't remember a second one toward the back, and the screwhead was flat with a slotted drive head, but otherwise, I think it's the same.

[hucklefish]

On 7/13/2023 at 7:59 PM, hucklefish said:

Does anybody have a picture of the linkages on the back and sides of a J13 Nikki carburetor?

anybody?

[pidge]

Let me have look when I get in, in the morning. I work nights. 

[pidge]

J13 on my 521 with a Nikki carb. As far as I’m aware on ‘69 521’s came with the J13 here in North America  Let me know before I button it back up if you need more or a different view  

-Pidge
 

 

Edited July 19, 2023 by pidge

[pidge]

 

 

Edited July 19, 2023 by pidge

[pidge]

EDIT: I’ve started a thread in the 521 section as not to hi jack this thread regarding the throttle return spring. 
-Pidge

Edited July 20, 2023 by pidge

[hucklefish]

On 7/19/2023 at 5:05 AM, pidge said:

Let me know before I button it back up if you need more or a different view  

Thanks a ton - super helpful!

[hucklefish]

I've got a new puzzle. Going about 65 on the freeway, suddenly felt just like I was running out of gas. I was only three miles from an exit with a station, so I coasted as far as I could, eventually had to face reality and pulled over, tried starting it again a couple times, and no luck. Called my wife to bring me a can of gas, poured in the 2-3 gallons she brought, dripped some into the carburetor, and tried starting. Start, but died as soon as it burned off the gas I dripped in. I took a closer look at the carburetor and found the float resting on the bottom of the bowl with a few drops of gasoline, and the see-through fuel filter on the fender had no fuel flowing into it even though I could hear the fuel pump whining (electric, 2-3 psi, mounted on the frame rail below the driver's door). I called a friend and he suggested that if the line from the tank comes off the top of the tank (it does), and if it was dry, the fuel pump might be starved and too weak to prime itself from a nearly empty tank, so I might try filling the tank the rest of the way. Wife and I went and bought another gas can and a funnel, filled both cans up, and went back to the truck. The funnel was so I could take the stupid leak-preventer gimmick off the gas can spout and pour straight from the can into the funnel instead of having to hold the thing open and get gas all over my hands every time I shifted slightly and it quit working. I bungeed the funnel to the bed rail and started pouring gas in. Not worried about overflowing the fill pipe with the first can, because it's a 10.8 gallon tank and I "knew" I only had a couple gallons in it so far. About 3.5 gallons into the first can, the fill pipe overflowed. So it can't have been actually out of gas, right?

 

So I put the can down, watched the gas slowly drain away from under the gas cap lid, replaced the gas cap, put the can away. I turned the key to on, got down beside the driver's door and verified I could hear the fuel pump running, and stepped forward to see if there's fuel in the filter and bowl. First thing I see is the fuel filter full and flowing. Next thing I see is the float still resting on the bottom of the bowl and gas fountaining out of the top of the carburetor. I rushed back and turn the key off, then cam back to look at the carb again. Standing gas in both barrels, gradually draining down into the manifold. So I took the glass plate off the front of the float, carefully caught the tiny brass collar on the end of the float axle, teased out the float while holding the needle valve up out of the way with a flathead screwdriver, then caught the needle valve. I wiped a trace of rusty gas out of the bottom of the bowl but saw no other problem. Stuck the float back in and found that it seemed to kind of catch on a little bump in the bottom that might be the port into the accelerator pump cylinder. I thought maybe the tiny brass collar was supposed to go behind the float to hold it out away from the back wall of the bowl, so I tried assembling it that way, but it definitely goes in front, which I verified by pulling up carpartsmanual on my phone. I reasoned that maybe the float only catches on that bump in the rare event that the bowl runs dry, so I reassembled everything and tried the fuel pump again.

 

I can't remember now whether I got the fuel fountain again or the dry bowl next. I only remember that I took it apart and reassembled it 3 or 4 times after that, and one of those times I took the fuel strainer and inlet apart thinking it would be more effective to drop the needle valve in from above (doesn't work), and another time I bent the metal tabs slightly on the float to try to adjust for less pressure on the needle valve, or more. I probably tried both. At some point it started raining, and I reassembled everything and tried one more time, then called a tow truck.

 

I haven't looked at it again since getting it home. I got a new radiator for my other work truck and have been busy putting that in and driving the family car for work. This evening and tomorrow I plan to disassemble the carb at least partway and clean and reassemble it, checking for obstructions and adjusting the float properly according to directions I assume I'll find either in the service manual or somewhere online. I'm guessing I can fix the float sticking to the bottom by adjusting it properly and not running it completely out of gas again. But I'm still puzzled by the initial "running out of gas" with half a tank. It wasn't nearly as hot as other recent days, so I wouldn't think it was vapor lock. The fuel filter is brand new and there's no sediment in it. The fuel pump was running every time I turned the key on, and obviously has enough pressure to deliver gas to the bowl when it has gas to pump.

 

The only explanation I've thought of is that this might have been the first time I've run the gas tank down to half full or less since I swapped the lower pressure pump for the one PO had installed, that was flooding the carburetor, and maybe the lower pressure fuel pump is too weak to maintain its prime once the fuel level drops that far, at least at freeway speed. If so, I'm thinking I need to switch back to the more powerful pump and add a pressure regulator and a return loop. Or don't drive on the freeway when it's below half a tank.

 

Anybody have any other suggestions?

Edited August 11, 2023 by hucklefish

[Stoffregen Motorsports]

Couple questions.

 

1- Where is the fuel pump mounted? Too high or too far from the tank and you could have siphon problems.

 

2- Are there more than one nipple sticking out of the tank that you can hook up hoses to? The fuel pickup tube extends to the bottom of the tank, but a return may only extend part way into the tank.

 

3- Does the needle and seat have a "rubber" tip or is it all brass? Sometimes you need to lap the needle valve into the seat to get them to work smoothly. Sometimes the rubber tip gets sort of sticky and can hang up.

 

4- Does the sound of the pump change at any time? If it drops to a lower rpm at idle, it may not be getting enough voltage. If it sounds like its running away, it could be cavitating or starving.

 

You're going to have to start all the way back at the tank and verify that none of the lines are clogged (even the pickup tube into the tank and yes, even the vent line, if there is one.) You'll also need to verify fuel flow at various spots in the system, at the pump, at the filter, at the carb, etc.

[datzenmike]

J13 fuel pump is just under half way up the block on the left side between cylinders one and two..

[hucklefish]

The pump is under the driver side door on the frame rail. It's a low pressure pump that replaced the higher pressure pump PO had on there. I don't have the original mechanical fuel pump, but this electric one is closer to the tank and lower than the original position on the block.

The needle is all brass with a seating surface that looks sort of blackened by some kind of coating (looks like factory applied, not some kind of deposit).

I'll look at the top of the tank, but I've had it nearly empty before (with the original electric fuel pump) with no problems. The only variable from that time to this is the new fuel pump and some tinkering with the linkages on the carburetor (throttle and choke cable mounting, throttle return spring, and test-fitting a 3d printed  prototype of a choke cable mounting bracket).

I'm going out right now to adjust the float and remount the carburetor with the new throttle cable bracket, and I'll upload some pictures of everything when I get done.

[Stoffregen Motorsports]

The black on the tip of the needle valve could be corrosion from the new fuel.

 

Edit- more like oxidation than corrosion.

Edited August 13, 2023 by Stoffregen Motorsports

[hucklefish]

13 hours ago, Stoffregen Motorsports said:

The black on the tip of the needle valve could be corrosion from the new fuel.

Nah, I'm pretty sure it's a factory finish of some kind (black oxide maybe?):

Edited August 14, 2023 by hucklefish

[hucklefish]

In putting everything back together I found this screw in the middle of the bottom loose again. As far as I can tell it's just one of the screws that hold the top and bottom half together, and even though it has a hole clear through it, doesn't seem to meter fuel in any way. So I put it back in with a few drops of blue loctite about the middle of the threaded portion. The black greasy looking stuff is non-hardening gas-safe Permatex.

[hucklefish]

Here are a few pictures of the new throttle cable bracket and its prototyping process.

 

One of the first 3d printed prototypes, missing a bolt hole tab on the left that broke off when trying to force it over the carburetor studs. The piece laying in front was screwed to the right end with the throttle cable passing through the necked down hole between them.

 

Final 3d printed prototype fitted in place and working okay with all clearances verified. I'm measuring the throttle cable lever here because I wanted to change the angle of the throttle cable, but it wouldn't make a difference to the rest of the design.

 

Here's the 3d printed prototype a few hours later, after about half an hour of engine idling while I drained and flushed the cooling system.

 

PLA+ isn't very heat-resistant, but I figured this would work long enough to verify that I could start and idle the engine and work the throttle linkages through their full range of motion with no interference.

 

Here's the metal design, still in its vacuum packaging from sendcutsend:

 

For more on how I used CAD, 3d printed prototypes, and sendcutsend, see my other post here on my alternator bottom bracket:

 

Here's the main bracket in its original shape. They sent me 2 for some reason even though I only ordered one. Last minute I started thinking about where to attach the throttle return spring and decided to add the tall leg up to support the choke cable bracket above and maybe attach the spring somewhere between the two brackets. The extra little angle piece is in case I needed to reinforce the leg up. I would have riveted it to the near face, but I'm glad it wasn't necessary because it would have been right in the way of the throttle cable clamp (the little piece on the lower left corner of the vacuum pack card in the previous picture - it fits into the slot next to the bottom of the leg up). 

 

 

I drilled and tapped holes for 10-32 screws in the top of the leg up and on the face of the tab down below the slot. Sendcutsend's bending options are limited to air gap bends 90° or less, so I had them make the bends I needed on each end of the cable clamp and then I used an assortment of needlenose vise grips and lineman's pliers to bend it into a U shape around a 5/32" drill bit. I don't have a picture of that, but you can kind of see it in the following pictures of the bracket installed on the carburetor.

brake cylinder gets in the way here, but you can see I had to twist and bend that leg up a little bit to get it aligned with the hole that was already there in the choke cable bracket. I also gave up on a creative new attachment for the return spring, because it's just too long to go anywhere besides on the choke cable bracket. Also, that's the original choke cable housing I'm holding, where it belongs (aftermarket one coming in from the lower left will have to be good enough until I can manage to drill the old cable out of the original knob extension and replace it):

looking at it from the back, you can barely see the jam nut I put on the back of the screw through the cable clamp:

And in this more straight-on side view you might be able to see that I slightly straightened the little arm on the other throttle lever on the back so that the return spring has a straighter pull from the choke cable bracket and not get so wrapped around the ball-end linkage. Still far from perfect, but getting better.

 

Edited August 15, 2023 by hucklefish

[hucklefish]

And here's what I did to get the carburetor running again (though I haven't test driven it yet):

 

First, I removed the carburetor and adjusted the metal tabs on the float until it would sit approximately level with the carb upside down and not go all the way to the bottom of the bowl with the carb sitting upright. I don't have any pictures of that process.

 

Here's the float bowl marked up with some colored arrows to explain what's what:

The black arrow is pointing at a tiny brass spacer (carpartsmanual calls it a collar) about 1/8" long, which I managed to avoid dropping on the side of the freeway, but which I forgot to put back in the last time I reassembled the bowl glass on the side of the freeway, and it rode all the way home in the little depression in the top of the radiator cap. Since then I've twice dropped it through the engine compartment into the gravel of my parking spot, but managed to find it so far.

The red arrow is the bottom end of the needle valve. All you can see of it here is a little spring-loaded rod that projects from the bottom of the brass barrel. It rests on the float height adjustment tab (yellow arrow). I bent this tab until the float sat approximately level with the carburetor sitting upside down. The green circle in the lower left is around what I think is a port that allows gas to flow into the accelerator pump cylinder. It bumps out about 1/8" from the wall of the bowl, and the float gets stuck on it if it goes all the way to the bottom. I adjusted the float stop tab (blue arrow) until it stopped the float from reaching that bump.

After these basic adjustments, I reinstalled the carburetor and turned on the key to run the fuel pump, and got no fuel into the bowl. I took the glass plate off the front and tried prying the float height adjustment tab down with a screwdriver between it and the bottom of the valve assembly (the brass part just above the end of the red arrow). I couldn't seem to get enough movement, so I came inside and looked for more info, Somewhere I found a forum post mentioning a gasket between the fuel inlet and the needle valve assembly that could be doubled to increase clearance between the float tab and the needle valve. I don't remember if it was talking about a J13/Nikki, or some other Datsun model altogether. But my needle valve assembly had an aluminum gasket on top and bottom that looked identical. The one on top had been kind of crushed by the bottom of the fuel inlet fitting. I pried it off carefully with a sharp knife and put it on the bottom, reassembled everything, and she works perfectly and doesn't leak gas anywhere (yet!).

 

Here's a closeup of the float adjustment tabs:

 

and here's a closeup of the gaskets under the needle valve assembly - hard to see, but if you look at the right side you can see a line between the two gaskets (aluminum washers between the pot metal of the carburetor top and the brass needle valve assembly, the six-sided brass part):

[datzenmike]

12 hours ago, hucklefish said:

Nah, I'm pretty sure it's a factory finish of some kind (black oxide maybe?):

 

 

 

 

 

 

   

That is a neoprene 'rubber' tip. Earlier than the mid 60s solid the tip was brass or some other soft metal in effect like a valve and seat. When installing you tap them with a hammer to set the two metal parts. These were replaced with 'rubber' tips that are flexible and seal much better.

 

 

 

11 hours ago, hucklefish said:

In putting everything back together I found this screw in the middle of the bottom loose again. As far as I can tell it's just one of the screws that hold the top and bottom half together, and even though it has a hole clear through it, doesn't seem to meter fuel in any way. So I put it back in with a few drops of blue loctite about the middle of the threaded portion. The black greasy looking stuff is non-hardening gas-safe Permatex.

 

That's to allow a vacuum signal up to the power valve, may even be the power valve. Later Hitachi have the valve at the top of the air horn. The power valve operates under heavy load and makes the secondary run richer for better power when floored and the secondary open. I wouldn't be using that sealer all over the bottom. It will squish out into the intake and the carburetor will be difficult to remove next time. Nissan didn't use it. Just use the proper gasket or make one.

[hucklefish]

Is the proper gasket cardboard? I made one from a Felpro cardboard that's supposed to be good for carburetors. It wasn't bad, I just thought it could be better sealed.

 

I'm pretty sure the black tip isn't rubber - this carburetor is less than a year old (from Thailand I think previous owner said), and that tip is at least as hard as the rest of the needle. I'm pretty sure I could scratch some of it off if I tried, and it feels and looks exactly the same as the coating/finish on a sheetrock screw, which is black oxide, and which I understand can be applied to brass for corrosion and wear resistance.

 

Vacuum signal makes sense - whatever is on top of it doesn't just fall out, so it must be a spring-loaded valve or whatever? Or just an open passage? Looking at the carpartsmanual diagram, it looks like the upper end of it must be right next to the big hole near the center top.

Here's a carburetor on eBay that looks exactly like mine: https://www.ebay.com/itm/263743348020?chn=ps

I'm thinking that screw must come up right below where the red circle in this picture:

The secondary is the barrel on the right. Could that large hole next to the red circle be the power valve? Gas was coming out of that hole when the float was stuck down. So I'm guessing gas is delivered to that hole (power valve hole) via an always-open port in the float bowl, and higher than normal vacuum delivered through the hollow screw opens a spring-loaded valve in the bottom of power valve hole, which allows it to be sucked through a port into the venturi in the secondary barrel.

 

I also see that carpartsmanual shows a lock washer that I'm missing on top of the hollow screw. That would probably be better than blue Loctite, so if I ever take this carburetor apart again I'll try to remember to make that switch.

Edited August 14, 2023 by hucklefish

[datzenmike]

A little checking shows that the needle has a specially hardened tip to reduce wear for the life of the carburetor. Did not know..

 

 

On the other Hitachis the hole has a hollow screw. Vacuum goes to the top of the carburetor and the vacuum pulls a plunger down into the float chamber where the power valve is.

 

 

 

[hucklefish]

Would you guys have any ideas about why my starter pilot bushing keeps coming out? I've got replacement bushings, and I've got a replacement nosecone, but I'm afraid if I just keep replacing them I'll burn through them pretty quick. Is the bushing supposed to be peened or chiseled to lock it in place or something?

Also, this time it's not just the pilot bushing coming out, and I don't know what happened first. The top bolt that holds the starter on fell out completely and the bottom bolt loosened to the point that the starter was hanging at an angle, and the starter pinion gear shaft is a lot more wobbly than I remember it being last time I had the starter out. So, I guess I should also ask if you guys have any idea why the starter bolts would loosen.

Edited August 27, 2023 by hucklefish

[Stoffregen Motorsports]

It should be a press fit. If in doubt, apply some Loctite sleeve retainer to it before you install it, and then for extra insurance, peen around the edges of the nose cone to keep it locked in place. There's no guarantees here,  just added insurance.

[datzenmike]

It should tap in place with a soft hammer. The pilot bushing is the same for most Datsuns and Nissans. Yours is part # 32202-30000 and used to at least 2004 and probably today if Nissan still uses manual transmissions.

 

It's made of powdered bronze hydraulically pressed into shape then heated and lightly melted but still porous then soaked in oil for lifetime lubrication. Don't know if Locktite will hold it.

[hucklefish]

Maybe I'll peen it on both ends. I'm more worried by the whole starter coming loose last week. Could that happen because of the pilot bushing being knocked out and then the pinion gear becoming crooked enough from repeated starting with pilot bushing, which then maybe caused enough vibration to loosen the bolts in spite of lock washers?

Looks like the only option for a new starter is from Germany or England, running $200-250 with shipping, so I want to make sure I'm installing it right.