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Old 07-11-2003, 08:55 AM   #1 (permalink)
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Aisin carb secondary guestion

So how do you tell if the secondary barrel and/or diaphragm on an Aisin carb(1980-87 vintage) is working/kicking in?

I have searched(here and LCML) and didn't find much. I see on my 60 or 40 carbs a rod which pulls(or is it pushing) on the secondary diaphragm, but I read that it's vucuum contolled.

is there a test I can do? or do I need to pull the diaphragm apart and look at it? I don't do well with small parts

John
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Old 07-11-2003, 11:37 AM   #2 (permalink)
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You can get some idea of the secondary function by just looking down the carburetor. If the primary side (passenger's side) is dirty and the secondary side (driver's side) is substantially cleaner, then there is a good chance the secondary is not opening. The reason for the difference is that no air (meaning here no dirt either) is moving through the secondary side. Remember, the secondary side is open less often than the primary, but the two sides should be fairly equal in dirtiness.

There is no real dependable way to fully check the function. You can try revving the engine at higher rpms while looking under the hood but on an FJ60 it is easy to lose sight of the arm under all the vacuum lines. And if you do see it move it is difficult to judge if it was complete or not.

Also, the diaphragms (found on 1/75-8/87) only last about 3-5 years. After that they develop small cracks and pin holes that reduce and then eliminate function over time.

You can pull the secondary off the carburetor while on the truck, but it is easier to work with off. Just two screws hold the secondary housing on the body and one e-clip on the activating rod. These two screws can be tight; a Phillips impact driver will take care of them.

There are two secondary diaphragm designs. One straight shaft for the 1/75-7/80 and the bent shaft for 8/80-8/87. These are frequently mixed up so make sure to get the correct one.

Toyota still offers the diaphragms but they are $20-75 depending on your dealer/discount. Aftermarkets are available and are $7-12. Here are some part numbers for the bent shaft secondary diaphragms:

Beck Arnley 167-0008
Niehoff FS468
NAPA (Echlin) CRB-24093

A few pics follow.
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Old 07-11-2003, 11:40 AM   #3 (permalink)
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Old and new secondary diaphragms. These are the straight shaft (1/75-7/80) versions. You can see the cracks and tears in the old on.
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Old 07-11-2003, 11:43 AM   #4 (permalink)
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Pin holes in an old secondary diaphragm. This is with a light from below, so the white dots are holes. You can also see the cracks. I switched pics for the better view.
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Last edited by Lostman; 07-11-2003 at 12:34 PM.
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Old 07-11-2003, 11:51 AM   #5 (permalink)
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These two phillips screws hold the secondary diaphragm body to the carb (middle two, they will be behind the green and white VSV that sits in the holder).
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Old 07-11-2003, 11:53 AM   #6 (permalink)
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This is the e-clip that holds the arm to the shaft. Don't drop this little guy, nothing like trying to locate metric e-clips this size.
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Old 07-11-2003, 12:19 PM   #7 (permalink)
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Eric, AWSOME info, thanks a million, I will check em out.

I ask because, say in 3rd gear at 35-40 when I punch the skinny pedal the mustard 82 fj40 runs like a raped ape compared to the green 82.....and I would say the same for my fj60. all 3 have the same power when just cruising along, but at WOT the mustard 40 is so fast(LOL) it is almost scarry.

Me thinks I need a diaphragm or two.

thanks again.

John
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Old 07-11-2003, 12:21 PM   #8 (permalink)
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Eric...

Nice photo's!

On another make, with vacuum secondary, there was a small check ball (slow pull, fast release) that was easy to loose. Trying to remember if such a critter was hiding in the FJ60 carb.

One other trick was to make a weaker spring. Allowed the secondary to open a little sooner for more power (& worse mileage).

Tom
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Old 07-11-2003, 12:41 PM   #9 (permalink)
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Quote:
On another make, with vacuum secondary, there was a small check ball (slow pull, fast release) that was easy to loose. Trying to remember if such a critter was hiding in the FJ60 carb.
Quote:
One other trick was to make a weaker spring. Allowed the secondary to open a little sooner for more power (& worse mileage).
Tom,

No such check valve on the FJ carbs (25/40/55/60 and carbed62).

Secondary springs with various tensions (resistance) are available for Holley's and other domestic carbs, none for the Aisans. You can cut the spring on the Aisan, but I don't think it really gives much. You can also modify the Aisan carburetor to be a mechanical two barrel, but you give up off road performance for a faster ride.
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