3/69-9/69 2BBL Aisan Carb Help

[brackenb5]

Hello all.

I have a 3/69-9/69 2BBL Aisan Carb whose secondary butterfly never appears to open. I have removed the air filter and visually watched the secondary as I manually revved the engine but the secondary never opens. I have revved it to roughly half throttle and quickly pushed it past half throttle to see if there would be any change but have had no luck.

At what point should it open? Are there other tests I can perform to determine if it is working properly?

Thanks in advance for all your feedback
Bracken

 

[BJEC69]

I can't answer your question, but you should call Marksoffroad.net. I had the same carb, and he recommended the I upgrade to the later style carb for better reliablity and performance. He built me a carb, and ported it for use with the non-USA spec vacuum advance distributer. I am happy with the upgrade, and Mark is a wealth of knowledge and an honest guy to do business with. Good luck!Brendon

 

[Pighead]

That's that stupid early vacuum-secondary carb? I hear they suck.
If you can manually move the secondary butterfly easily, then I would have to suspect the vacuum diaphragm. I have read of the "Paper clip test" for the newer vacuum-secondary, do not know how to test on yours.
I vote that you spend your money on another year Aisan carb.

 

[brackenb5]

That's that stupid early vacuum-secondary carb? I hear they suck.
If you can manually move the secondary butterfly easily, then I would have to suspect the vacuum diaphragm. I have read of the "Paper clip test" for the newer vacuum-secondary, do not know how to test on yours.
I vote that you spend your money on another year Aisan carb.

Trying to save a buck and I am not sure how I will present another purchase to the boss .... The diaphragm is in good shape (took it apart and inspected it) and resistance is present when manually moving the secondary. I was trying to figure out how the vacuum on this thing works but have had no luck. In analyzing the diaphragm I noticed there is a hole in the upper part of the casing. I verified this hole is not plugged (blew air through it). I even left the enclosure open and ran the motor to see if there was any type of vacuum present in the diaphragm housing, but there did not appear to be any. What is the "Paper clip test"?

 

[texfj40]

I have the same Aisen 2bbl carb on my F. You can listen to what others in this thread have to say; but I sent mine to Mark for an overhaul and it operates perfectly. Instant starts, no hesitation, 2nd bbl kicks in for the extra boost when desired. This carb uses a mechanical distributor (mine is electronic), not vaccum operated. The reason I sent mine to Mark was that the throttle butterfly valve had worn an oval in the throat of the carb from decades of use, and there was a small fuel leak upon shutting down the engine. I'd say 40+ years and lord knows how many thousands of miles created this wear....nothing lasts forever, even Toyota carbs.

To answer your question, look on the front of the carb facing the radiator. At the lower front, you will see the linkage which kicks in the second bbl. Operate the main throttle linkage to verify the movement and you will be able to see how this simple mechanism works. Maybe a previous owner did something to modify it?

Mark also suggested replacing the carb, but entailed a new distributor, air cleaner, plus the carb, etc. and that was not in my plan and I am happy I did not replace it. Very happy. Throttle response is terrific and my F engine runs smooth, idles at 650 rpm and can balance a dime. I have seen plenty of F engines over the years, and I can compete with the best with this carb.

Good luck....

 

[brackenb5]

I have the same Aisen 2bbl carb on my F. You can listen to what others in this thread have to say; but I sent mine to Mark for an overhaul and it operates perfectly. Instant starts, no hesitation, 2nd bbl kicks in for the extra boost when desired. This carb uses a mechanical distributor (mine is electronic), not vaccum operated. The reason I sent mine to Mark was that the throttle butterfly valve had worn an oval in the throat of the carb from decades of use, and there was a small fuel leak upon shutting down the engine. I'd say 40+ years and lord knows how many thousands of miles created this wear....nothing lasts forever, even Toyota carbs.

To answer your question, look on the front of the carb facing the radiator. At the lower front, you will see the linkage which kicks in the second bbl. Operate the main throttle linkage to verify the movement and you will be able to see how this simple mechanism works. Maybe a previous owner did something to modify it?

Mark also suggested replacing the carb, but entailed a new distributor, air cleaner, plus the carb, etc. and that was not in my plan and I am happy I did not replace it. Very happy. Throttle response is terrific and my F engine runs smooth, idles at 650 rpm and can balance a dime. I have seen plenty of F engines over the years, and I can compete with the best with this carb.

Good luck....

Thanks for the info. The linkage on the front that your referring to does not appear to do much. On initial examination I did notice the linkage was bent so I bent it back (no change in operation) and it operates smoothly. It is hard to tell if anything is missing but the linkage only seems to limit how far the second will open. That being said the linkage causes it to open just a fraction when about half throttle but it never opens any more.

 

[IOKRU2]

I recently had a similar issue. My secondary would not open and my cruiser would not stay running unless I manually held it open a bit... which is not the way things should work. I had taken apart my base and I think I messed my primary butterfly angle up as well.

Instead of buying a new carb, I just bought a rebuild bottom half (vacume ported carb base) from Spector Specter Off-Road Land Cruiser Parts - Search On 042-62

After I return my old they will refund my core charge of $80, total cost will be about $120.

Point being, I replaced my bottom half and now I am running great... plenty of power at cruising speeds so I assume the secondary is opening up when it needs to as intended.

 

[fj404life]

I have the oddball carb too (7-69). It seems to work fine. I also believe the secondary is linkage operated at the bottom front of the carb...not vac? I would pull the carb and clean it up and give it a good look over.

 

[brackenb5]

I have the oddball carb too (7-69). It seems to work fine. I also believe the secondary is linkage operated at the bottom front of the carb...not vac? I would pull the carb and clean it up and give it a good look over.

There is some linkage there but it does not seem to do much. The secondary is definitely controlled by vacuum.

 

[brackenb5]

So I finally got sick of trying to figure the carb out so I removed it and started a rebuild. I had a kit a purchased some time back from SOR so I figured I would give it a shot. The rebuild went smooth and made a world of difference. The rig now idles smoother and starts without the need of the choke. I still don't fully understand the secondary and it still does not appear to open much but maybe it is not suppose to open until its needed (apparently that saves gas). I have yet to test the trucks power but it ran good on a short trial drive.

Thanks everyone for your feedback!