Stock Carb Question

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Sep 30, 2003
Woodstock, GA
I have noticed that on my, I believe to be, stock Aisin carb the right barrel works but the left one never does (or has since I have owned it). It is a little cruddy down there and you can see that the choke flap never opens no matter how much the gas is depressed.

What should I start looking for first to determine what is going on? Short of a complete re-build....

I think the secondary on the '79 carb is vaccuum operated not mechanical. You won't see it open by depressing the gas.
It should be mechanically actuated on a 69. Make sure the linkage is attached correctly. At approximately 3/4 throttle, the secondary should open. See the picture below. The circled linkage is what opens the secondary. As the primary opens up, the secondary should remain closed until the linkage "bottoms out" at the end of the groove. Pushing farther, the secondary opens up.

Good luck! :cheers:
There is also a weighted throttle plate above the throttle plate. The bottom one should open mechanically and the top one only opens when there is enough airflow.

You can see the weighted one in the above pic, just to the left of the red circle.
I have seen a number of mechanical secondary carbs whose throttle shafts were frozen from lack of use. Usually this is because the cable, and even more likely gas pedal, are so far out of adjustment that the pedal hits the floorboard before the linkage engages.

You can try to simply rotate the shaft by hand. If it does not move, take off the carb and soak the base in solvent. If that does not release it, try some penetrant. In all but the most stubborn cases, that should be sufficient.


Mark A.
OK, I checked it out. My carb definitly looks different than the one above...I think. I was able to rotate the secondary shaft, which in turn opend the first as well, easily by hand and it had the desired effect. I did not locate the linkage above though (though I did find a different linkage that I had to re-attach but had not affect on performance) I will try to post some pictures I took of it last night to see what you all think.

Also, I have a newer gas pedal cable that seems to be adjusted perfectly.

Another question I have here is, on why I have never had to use the choke on my carb (will hinder the start if I do). It always starts imediatly. Would this indicate it is running rich?

Last edited:
Here is my carb. Looking from drivers side. Could not get any clear pics of all the linkages but you can see that It does not look like the one above.

I have pretty well determined that the engine is not numbers matching and may have even come from a Japanese fire truck.

Any help appreciated.
Carb 2.jpg
Any way to easily check the diaphram? I assume it is the piece in the pas side windo pic (rear part of carb). Can I just take of the top plate and inspect?

Any way to easily check the diaphram? I assume it is the piece in the pas side windo pic (rear part of carb). Can I just take of the top plate and inspect?


Yes, that is correct. Those screws can be a bear to get out. Looks like yours are a little rusty.
Mine had a hole in the diaphram that kept it from working. Good luck.
The odds of the diaphram working after all these years are virtually nil. And new ones are unobtanium.

If I had a good used one to sell you [and you'd have to CALL ME at the shop to remind me to look] I still don't know if it would be the right thing to do, as it may only last for a short while before putting you back in the same position again.

THe better option IMO is to consider upgrading to a 70-74 carb. You will need a different lid for your air cleaner, a different cable for your pedal, and a thinner insulator under the carb to make the swap, but other than that, it should be pretty straightforward.


Mark A.
Thank you everyone. Mark, you are an awesome resource! Thank you. I sent you a private message.

Guess it is time to upgrade the carb and see the power this engine is supposed to have. Wasn't as much as a problem in the flat city of Denver but these hills in GA are bogging this engine.

Off to do some searches on Webber carbs here (I believe most have preffered Aisin instead but need to make sure).
Looking forward to your call.:)

Users who are viewing this thread

Top Bottom