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junk250

I rebuilt my Hitachi carb, much better but...

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I did what I could with 2 cans of carb cleaner and a kit.

 

It was obvious the gaskets were shot and probably dirty jets.

 

After rebuild runs much better, the idle screw was turned all the way in and wouldn't effect the idle, after rebuild it would adjust normally (a turn out or so at idle).

 

This thing has 7 jets I think and is a pain to take apart, and put back together on and off the car ect.

 

First thing I noticed when I took the top off was the power piston was sticking , I took steel wool to the piston and bore and helped a lot.

 

The new accelerator pump is still leaking or something, I should have polished the bore there also.

 

It runs much better, but I still need to get the air/fuel mixture plug out(I didn't want to mess anything up) and I didn't clean the egr.

 

But one little problem, the throttle bypass valve fell out in pieces(not included in the kit) and obviously needs to be replaced.

 

There was a new symptom after rebuild, it was skipping/sucking down funny on deceleration, and I went straight to the valve I knew was bad and disconnected the vacuum and the skipping stopped but I know it wont be right unless I find one.

 

Throttle bypass valve, who's got one, the dealer maybe ?

Edited by junk250

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I Believe that Removing and Disassembling an Hitachi Carburator is a Good School to Learn about Carburator Maintenance, it is Not Easy to Do at all, but the main problem is not the many tricky things you'll need to realign, the main problem is the Metal Fatigue, much more noticeable on the metal alloy that hitachi used to build those carbs, so, they trend to be misaligned in certain spots, as you already noticed in the accelerator pump, but other areas also, that usually lead to certain malfunctions; such as the one you're experiencing now.

 

What I'm trying to explain is that the Hitachi carbs are Good when they're New, but they fail very much as they get old, because the metal gets misaligned beyond the tolerances.

 

I don't know if you live in an emissions regulated Area, that maybe somehow "Forces" you to Keep the old Hitachi carb, but if you could do an Swap, I kindly Suggest to swap a Weber carburator; not only for its simplicity and increased eficiency, but also because it will last much longer than the Hitachi... maybe even longer than the engine itself.

 

But if you want to Fix that issue(s) on the Hitachi, you must take off it again and measure the flatness of each surface to be mated, and rectify them as needed.

 

Good Luck!

Kind Regards.

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The dealer is not going to be able to help you with that one.  Can you post up a photo of the part you're referring to?  I don't see a throttle bypass valve listed in the FSM.

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I Believe that Removing and Disassembling an Hitachi Carburator is a Good School to Learn about Carburator Maintenance, it is Not Easy to Do at all, but the main problem is not the many tricky things you'll need to realign, the main problem is the Metal Fatigue, much more noticeable on the metal alloy that hitachi used to build those carbs, so, they trend to be misaligned in certain spots, as you already noticed in the accelerator pump, but other areas also, that usually lead to certain malfunctions; such as the one you're experiencing now.

 

What I'm trying to explain is that the Hitachi carbs are Good when they're New, but they fail very much as they get old, because the metal gets misaligned beyond the tolerances.

 

I don't know if you live in an emissions regulated Area, that maybe somehow "Forces" you to Keep the old Hitachi carb, but if you could do an Swap, I kindly Suggest to swap a Weber carburator; not only for its simplicity and increased eficiency, but also because it will last much longer than the Hitachi... maybe even longer than the engine itself.

 

But if you want to Fix that issue(s) on the Hitachi, you must take off it again and measure the flatness of each surface to be mated, and rectify them as needed.

 

Good Luck!

Kind Regards.

 

I'd love to have a Weber but I just cant afford one, the Hitachi carb kit was only 6.00 lol.

 

I know what you are saying about the warped tops, but it seems to be working good.

 

I wasn't getting very good mileage with the leaky gaskets, I expect the mileage will be much better now.

 

Edit: I forgot to say the float level was WAY out of whack when I took it apart, float is now set right.

 

Thanks

Edited by junk250

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The dealer is not going to be able to help you with that one.  Can you post up a photo of the part you're referring to?  I don't see a throttle bypass valve listed in the FSM.

 

Here is a pic of it,  #10 Throttle bypass valve.

 

It mounts directly to the carb on the back, below the other two vacuum pull offs that are on a bracket.

 

It is supposed to have some sort of a seal on the plunger, mine was MIA.

 

I have the o ring seal from the kit, but the valve is missing its rubber seal.

 

Its a 1979 DL EA-71.

 

 

 

hitachiDCD-306-1.png

Edited by junk250

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I see.  Looks like the carb you have is significantly different than the 80s models.  Unfortunately all my parts carbs are from the 80s so they don't have that part.  

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