Hesitation upon accelerating from a stop

[LenRobertson]

I read over some of the past threads of the trials and tribulations of the Hitachi carb.  

Here's a few more questions.

1. How can you know if the carb is original Hitachi and not a remanufactured or knock off carb? 

2. What's a good carb body cleaning solution for soaking the parts in? 

3. How long to soak the parts? I understand the middle portion with the circular float window shouldn't be soaked "too long" due to rubber being a component of the window and is a recommended warning on the carb rebuild kit I have. 

4. To clean the jets, should they be accessed from the inside, unscrew the top ceiling screws and removed/cleaned? Do those top screws to access the jets have a certain position/depth or are they screwed in to the lowest position? 

5. Should gasket sealer be used on carb to carb gaskets and/or carb to manifold gasket? 

6. I currently do not have a clamp on the lower end of the Manifold heat riser white tube that leads to the neck of the air cleaner assembly. Would this cause vacuum loss? 

7. When removing the carb from the car, how can the metal cable coming from the firewall be detached to free the carb? 

 

Thanks!

1. I don't think there were ever knockoff Hitachis. The only way to know if you have an original-to-the-car is find the elusive numbers on the side of the carb body and see if they match what the Factory Service Manual says. Probably any of your carbs will be fine, although with an auto tranny having the version with a dashpot might be good. The dashpot from an auto version can probably be swapped onto a manual carb.

2.I don't know how good it is, but I got a 1 gallon bucket of carb cleaner from Autozone. It has a metal basket in the bucket to hold small parts.

3.The cleaner directions should tell you how long to soak. I'm remembering something like 20 to 30 minutes for the Autozone version. Something with rubber parts may not even have to be soaked in cleaner. The cleaner is mainly to dissolve dried gas/varnish in the small holes and passages. If you leave the body parts in carb cleaner too long (like overnight) it can take the surface finish off and maybe even start to etch into the threads in the body.

4.To do a proper job, all the jets and air bleeds and all that stuff should be unscrewed from the body and soaked in cleaner. It isn't very hard to draw a diagram of what part goes in what hole. To reinstall, just tighten everything down good and snug. For removing the power valve on a Hitachi 340, I ground a notch in the center of a screwdriver blade to clear the pin, but I don't remember if the A-series carbs have the same sort of power valve. You should have compressed air to blow out all the passages.

5.No gasket sealer anywhere in a carb.

6.I'm not familiar with the heat riser, but the ones I've seen on American cars don't have anything to do with vacuum.

7.I don't know if your throttle cable is the same as the one on my F10 or not. Mine has a metal slug cast onto the carb end of the cable. Taking the cable bracket near the carb loose allows slack in the cable enough to move the cable and slug sideways out of the throttle arm on the carb. I know I'm not explaining this well, but look carefully at how the cable hooks at the carb and think "slide sideways". There should be a slit for the cable to move through to one side. Or you may have a different hookup than I do.

 

I'm typing this in kind of a hurry so I hope it isn't too garbled.

[jboulukos]

1. I don't think there were ever knockoff Hitachis. The only way to know if you have an original-to-the-car is find the elusive numbers on the side of the carb body and see if they match what the Factory Service Manual says. Probably any of your carbs will be fine, although with an auto tranny having the version with a dashpot might be good. The dashpot from an auto version can probably be swapped onto a manual carb.

2.I don't know how good it is, but I got a 1 gallon bucket of carb cleaner from Autozone. It has a metal basket in the bucket to hold small parts.

3.The cleaner directions should tell you how long to soak. I'm remembering something like 20 to 30 minutes for the Autozone version. Something with rubber parts may not even have to be soaked in cleaner. The cleaner is mainly to dissolve dried gas/varnish in the small holes and passages. If you leave the body parts in carb cleaner too long (like overnight) it can take the surface finish off and maybe even start to etch into the threads in the body.

4.To do a proper job, all the jets and air bleeds and all that stuff should be unscrewed from the body and soaked in cleaner. It isn't very hard to draw a diagram of what part goes in what hole. To reinstall, just tighten everything down good and snug. For removing the power valve on a Hitachi 340, I ground a notch in the center of a screwdriver blade to clear the pin, but I don't remember if the A-series carbs have the same sort of power valve. You should have compressed air to blow out all the passages.

5.No gasket sealer anywhere in a carb.

6.I'm not familiar with the heat riser, but the ones I've seen on American cars don't have anything to do with vacuum.

7.I don't know if your throttle cable is the same as the one on my F10 or not. Mine has a metal slug cast onto the carb end of the cable. Taking the cable bracket near the carb loose allows slack in the cable enough to move the cable and slug sideways out of the throttle arm on the carb. I know I'm not explaining this well, but look carefully at how the cable hooks at the carb and think "slide sideways". There should be a slit for the cable to move through to one side. Or you may have a different hookup than I do.

 

I'm typing this in kind of a hurry so I hope it isn't too garbled.

Fantastic info.  Much appreciated!

[jboulukos]

1. I don't think there were ever knockoff Hitachis. The only way to know if you have an original-to-the-car is find the elusive numbers on the side of the carb body and see if they match what the Factory Service Manual says. Probably any of your carbs will be fine, although with an auto tranny having the version with a dashpot might be good. The dashpot from an auto version can probably be swapped onto a manual carb.

2.I don't know how good it is, but I got a 1 gallon bucket of carb cleaner from Autozone. It has a metal basket in the bucket to hold small parts.

3.The cleaner directions should tell you how long to soak. I'm remembering something like 20 to 30 minutes for the Autozone version. Something with rubber parts may not even have to be soaked in cleaner. The cleaner is mainly to dissolve dried gas/varnish in the small holes and passages. If you leave the body parts in carb cleaner too long (like overnight) it can take the surface finish off and maybe even start to etch into the threads in the body.

4.To do a proper job, all the jets and air bleeds and all that stuff should be unscrewed from the body and soaked in cleaner. It isn't very hard to draw a diagram of what part goes in what hole. To reinstall, just tighten everything down good and snug. For removing the power valve on a Hitachi 340, I ground a notch in the center of a screwdriver blade to clear the pin, but I don't remember if the A-series carbs have the same sort of power valve. You should have compressed air to blow out all the passages.

5.No gasket sealer anywhere in a carb.

6.I'm not familiar with the heat riser, but the ones I've seen on American cars don't have anything to do with vacuum.

7.I don't know if your throttle cable is the same as the one on my F10 or not. Mine has a metal slug cast onto the carb end of the cable. Taking the cable bracket near the carb loose allows slack in the cable enough to move the cable and slug sideways out of the throttle arm on the carb. I know I'm not explaining this well, but look carefully at how the cable hooks at the carb and think "slide sideways". There should be a slit for the cable to move through to one side. Or you may have a different hookup than I do.

 

I'm typing this in kind of a hurry so I hope it isn't too garbled.

 

I'll examine the carb on my car, however out of my extra 3, 2 have dashpots.

 

I'm pretty sure the throttle cable is unhooked at this exit point as you were describing.

 

 

Need to know all the details to do it right and limit the potential of failure.  Much thanks, each small piece of info is a big deal to me.

[Cosmonaut]

Not to b a turd, but all properly working chokes have to b set (closed) when first starting the car...if in doubt google "how to set choke" its pretty universal

[Cosmonaut]

I have good working Hitatchi you can have. PM me your address...I will even pay for the shipping

[jboulukos]

I have good working Hitatchi you can have. PM me your address...I will even pay for the shipping

Great, I'll take it.

[jboulukos]

What is the proper/correct gasket set up for between manifold and carburetor?  

Here is my current set up.

 

[Cosmonaut]

What is under the heatshield?

[jboulukos]

What is under the heatshield?

 

The intake manifold i suspect. Here's a pic.

[jboulukos]

It was the choke that needs to be set...mind farted while typing...in this case clutch = choke

 

 

When driving the choke opens due to it being at operating tempature. It remains at that setting (after you have turned off the vehicle) untill you give the accelerator pedal a quick depression (once) to reset the choke (closed) for starting a cold engine.

 

I attempted another choke adjustment.  I understand how it's done however it seems the linkage won't allow the choke to close when the gas pedal is depressed.  Here's a picture of the choke mechanism stuck in a partially open position.  I have to manually lift the accelerator linkage to get the choke to close.

 

[jboulukos]

Can a slackened throttle cable be the culprit of hesitation upon acceleration?  I see the clamp were it can be slackened or tightened.  I have read there should be 1mm of play in the cable.  Mine has about 5-6mm of play.  The clamp can only grab the metal cylinder area on the cable to be tight.  I have moved the cable to the edge of the clamp and the metal cylinder around the cable is only being held by the edge of one side of the clamp.  In this position which is the end of the spectrum for tightening, slack remains.  There is even more slack if the cable is positioned completely on both sides of the clamp.  Here is a picture.  I hope I described it well.  

 

[Cosmonaut]

Should b a gasket between the manifold n heat shield.

 

 

On the accelerator cable, check the pedal to make sure it is returning properly. Measure for proper distance.

 

Is the choke rod binding? Check the butterfly valve for proper closure.

 

Possible, wrong carb/accelerator cable combination.

[jboulukos]

Should b a gasket between the manifold n heat shield.

 

 

On the accelerator cable, check the pedal to make sure it is returning properly. Measure for proper distance.

 

Is the choke rod binding? Check the butterfly valve for proper closure.

 

Possible, wrong carb/accelerator cable combination.

 

 

Thanks for the info.  Well my next step is to remove the carb and 1.) adjust fast idle cold as per service manual and recheck with warmed up engine, 2.) adjust choke unloader by bending the unloader tongue as needed as per service manual, 3.) It looks as though the dashpot position can effect the position of the throttle lever so I will look into that as well.

 

If you find any specific info on the gaskets necessary at the base of the carb to heat shield to manifold, let me know.  I'd like to get it what it needs. 

 

I'm thinking once the carb adjustments are dialed in, the throttle cable will fit normally.  

[LenRobertson]

I'm thinking you need three gaskets - manifold to heat shield, heat shield to phenollic spacer, and spacer to carb base. O'Reilly has individual gaskets on their website, but I've yet to try to order any through their store so the availability may be false hope.

 

http://www.oreillyauto.com/site/c/search/Carburetor+Flange+Gasket/02545/C0359.oap?year=1977&make=Nissan&model=B210&vi=1210813

 

There may be other sources of A-series carb gaskets but it seems NAPA and Autozone don't have them.

 

If you haven't done it already it is worth spraying the choke shaft and all linkages with carb cleaner to make sure nothing it sticking. I'll admit I don't really grasp the details of the choke linkage. It may be explained in the FSM. I believe it ties into the position of the fast idle cam, but that is more guess than knowledge.

 

Len

[jboulukos]

I'm thinking you need three gaskets - manifold to heat shield, heat shield to phenollic spacer, and spacer to carb base. O'Reilly has individual gaskets on their website, but I've yet to try to order any through their store so the availability may be false hope.

 

http://www.oreillyauto.com/site/c/search/Carburetor+Flange+Gasket/02545/C0359.oap?year=1977&make=Nissan&model=B210&vi=1210813

 

There may be other sources of A-series carb gaskets but it seems NAPA and Autozone don't have them.

 

If you haven't done it already it is worth spraying the choke shaft and all linkages with carb cleaner to make sure nothing it sticking. I'll admit I don't really grasp the details of the choke linkage. It may be explained in the FSM. I believe it ties into the position of the fast idle cam, but that is more guess than knowledge.

 

Len

 

Is the gasket in the O'Reilly's link, with the one opening, for the manifold to heat shield?   Also, is the phenolic spacer the clear red plastic looking one in my previous pic of the carb base gasket setup I currently have?  I will pull it apart and check under the heat shield.  I'm curious to know what the original set up is because it doesn't seem to show it in the blow up carb images in the service manual.

 

I've been practicing the cold fast idle adjustment on one of my extra carbs and it definitely effects position as it relates to dashpot, throttle and choke linkage or cams.  The service manual lays out specified measurements for gaps between areas so I will adjust everything appropriately.  One thing I have found with the carbs is that the metal arms on the throttle area and other movable arms can bend and/or twist slightly and thus effect the mechanisms and the smoothness of movement of the linkages.  

[jboulukos]

RockAuto "Carb Spacer"

Where would this go?  Between heat shield and carb base gasket?

 

[LenRobertson]

Is the gasket in the O'Reilly's link, with the one opening, for the manifold to heat shield?   Also, is the phenolic spacer the clear red plastic looking one in my previous pic of the carb base gasket setup I currently have?  I will pull it apart and check under the heat shield.  I'm curious to know what the original set up is because it doesn't seem to show it in the blow up carb images in the service manual.

 

I've been practicing the cold fast idle adjustment on one of my extra carbs and it definitely effects position as it relates to dashpot, throttle and choke linkage or cams.  The service manual lays out specified measurements for gaps between areas so I will adjust everything appropriately.  One thing I have found with the carbs is that the metal arms on the throttle area and other movable arms can bend and/or twist slightly and thus effect the mechanisms and the smoothness of movement of the linkages.  

I think the O'Reilly gasket may work for any of the three, although the one big opening is a bit puzzling. Gaskets for the bigger 340 Hitachis usually have two separate holes. I honestly don't know if the one big hole matters or not. There may be a source for a two holer that I don't know about. I've never pulled up the heat shield so I'm just assuming there is a gasket under it. Let me know what you find on yours.

 

Yes, in your pic the red plastic spacer is the phenolic spacer. Phenolic just refers to the type of plastic - very hard and durable and chem resistant. That is what Rock Auto lists as a "Carb Spacer". No reason not to reuse your old one unless it has big chunks or gouges out of it (unlikely).

 

The fit of your throttle cable in the clamp doesn't look right, but I'm not sure why. As Cosmonaut posted it could be an incorrect length cable. I can't remember if there is any adjustment at the pedal end inside the car. Any way to bend the arm at the carb that carries the clamp? I'm too lazy tonight to go look at the one on my F10. Maybe in the morning I can.

 

Len

[LenRobertson]

I forgot to mention it looks to me like the gasket under your phenolic spacer is thick, possible home made from sheet gasket material. It may be fine, but usually carb gaskets are very thin, maybe for a reason. The thick gasket may not have anything to do with your problems but you might look at it closely. Could it leak vacuum with the engine really warm? No idea really, just an observation.

 

Len

[Cosmonaut]

Agree with Len, stay away from homemade gaskets. I have never had good luck with them...I don't believe the cork comp gasket will stand up to fuel. Just a sidenote, if the throttleshaft has exesive play (worn), the carb will not operate properly.

[jboulukos]

I forgot to mention it looks to me like the gasket under your phenolic spacer is thick, possible home made from sheet gasket material. It may be fine, but usually carb gaskets are very thin, maybe for a reason. The thick gasket may not have anything to do with your problems but you might look at it closely. Could it leak vacuum with the engine really warm? No idea really, just an observation.

 

Len

 

Agree with Len, stay away from homemade gaskets. I have never had good luck with them...I don't believe the cork comp gasket will stand up to fuel. Just a sidenote, if the throttleshaft has exesive play (worn), the carb will not operate properly.

 

Exactly.  That's why I'm searching for the exact configuration of gaskets and spacer in order to limit the potential of issues in this area.  I checked datsun1200.com but did not find enough information regarding the order of gaskets and which ones to use.  

 

I'll recheck the throttle shaft once I pull the carb out. 

[jboulukos]

Ok carburetor is off.  The order of my current gasket/spacer set up from top to bottom is as follows.  Also see pictures.

 

carb

black thin paper gasket

red phenolic spacer

cardboard colored paper gasket

heat shield 

thin black plastic gasket

manifold

 

 

No throttle shaft play in currently used carb, minimal throttle shaft play in one of the extra carbs.

[LenRobertson]

It appears the gaskets on yours have one large oval hole rather than two round holes like gaskets for the Hitachi 340. So presumably the O'Reilly gaskets will work okay. Let us know if you are able to get them from O'Reilly, or if you find another source. I may need some for my F10.

 

Something I always forget to do when I have a carb off is adjusting the primary throttle butterfly when it closed, or rather almost closed.  I remember seeing a pic in the FSM of using a certain diameter drill bit between the edge of the butterfly and the side of the carb bore. I doubt this gets out of adjustment, but it is worth looking at and I think it can only be checked from the bottom of the carb.

 

Lest you think I'm anything like a carb expert, I've been working this morning on the Hitachi 340 on my 510 trying to get a better idle. So far I'm not getting what I want, but will keep messing with it. It may well be you will have a properly running carb before I do. :lol:

 

Len

[jboulukos]

Sounds good.  I have an AutoZone and an Advance Auto Parts nearby.  I will let you know if the have them.

 

So I tried to do some of the carb adjustments in the service manual.  I had a rough time for various reasons.  Here's a list of things I attempted.

 

1. adjusting fast idle screw (at bottom): using a feeler gauge to check clearance "A" was fine except the clearance(small gap in choke valve) did not change for me at I tightened or loosened the fast idle screw.  I threw in the towel.

 

2. vacuum break: clearance "B" should be between 1.8 to 1.98 mm.  I through in the towel due to not having a gauge to measure it.  My feeler gauge goes up to .635 mm.  

 

3. choke unloader adjustment: unable to bend the unloader tongue.  Can anybody?  See picture

 

[jboulukos]

It appears the gaskets on yours have one large oval hole rather than two round holes like gaskets for the Hitachi 340. So presumably the O'Reilly gaskets will work okay. Let us know if you are able to get them from O'Reilly, or if you find another source. I may need some for my F10.

 

Something I always forget to do when I have a carb off is adjusting the primary throttle butterfly when it closed, or rather almost closed.  I remember seeing a pic in the FSM of using a certain diameter drill bit between the edge of the butterfly and the side of the carb bore. I doubt this gets out of adjustment, but it is worth looking at and I think it can only be checked from the bottom of the carb.

 

Lest you think I'm anything like a carb expert, I've been working this morning on the Hitachi 340 on my 510 trying to get a better idle. So far I'm not getting what I want, but will keep messing with it. It may well be you will have a properly running carb before I do. :lol:

 

Len

 

Yeah, on the websites,  AutoZone and Advance do not have the "carb flange" gasket but O'Reilly's does. $2.99 ouch

[datzenmike]

Make your own!! Dollar store round hole punch, scissors and a cereal box. Trace out pattern on box, hole punch the round bolt holes. Hole punch the center to get the scissors in to finish. Or  buy thin gasket material and never worry about them again.