Topic: Aisan knock off carb lean

[opus]

Greetings all,

Too long of a story to go into but I ended up with a China knock off Aisan.  Actually, its a pretty good carb, to my surprise.  Get it all warmed up, idle it down low, adjust the idle, perfect.  Take it for a drive and the first bit of acceleration, which I would call the idle circuit as in a Weber, is bucking and popping, assuming its lean.  I'm a little more familiar with a Weber, in which case I would up my primary idle jet.
What do I do in this case?  Once I get out of the "primary" circuit, we're off to the races.

Also, in all my years of searching, this forum seems to be the only one with people that have a clue about these carbs.

[sirdeuce]

Check to see if the carb is actually pumping fuel when it's opened up (throttle). If the pump isn't working inspect the circuit check valve. If it's sticking open the fuel will just pump back into the bowl. If the pump is the plunger type, instead of a diaphragm, check to see if the pison skirt is folded up or cut. If diaphragm, check for complete sealing and holes.

[opus [OP]]

Its diaphragm and it pumps.  I took the top of the carb today, everything looks fine.  Blew it out but there was nothing plugged.  Jet is a 116 which I believe is correct.  I was thinking it was going to be smaller and seeing I am at 2500', but thats not the case. 

I have 2 of these carbs and they do the same thing.  I put an Aisan on that I rebuilt, and its fine. 

I dont know how these carbs work off idle up to main jet transition. Weber was easy but I dont like the Weber.

[opus [OP]]

Fast forward to now:

I have 2 of these knock offs, new.  I've had them off and on a dozen times, trying to figure out what the issue is.  I finally found it.  After taking one completely apart, right next to a bad oem one, to compare.  The jetting is all wrong in the body.  The main and primary jet are right but these 2 are wrong.  Not sure what they do but the jets are tiny compared to the oem.  This pic is OEM.


I took the top and bottom of the new carb, stuck my middle section and and its perfect.  Mind you, it took me a year of fiddling and digging to figure this out.

Now, to finally sell this Weber.....

[sirdeuce]

Weber 32/36? Or not?

[opus [OP]]

Weber 32/36? Or not?

32/36 Spain.  Rebuilt with various jets and the hood so you can use the OEM air cleaner.

[sirdeuce]

Hmmm. I need one for my Corolla.

[Gnarly4X]

.... Weber was easy but I dont like the Weber.

I ran Weber carbs for 8 years on my sand rails. 

Picky and fussy little bashturds!!

Keeping a Weber carb happy takes some experience and practice.

That's just my experience.

Gnarls.

[opus [OP]]

Could never get it to give me the fuel mileage I wanted.  I have tweaked on it for years.  Great carb but a good OEM is better for economy.

[Gnarly4X]

Could never get it to give me the fuel mileage I wanted.  I have tweaked on it for years.  Great carb but a good OEM is better for economy.

I believe the Webers are known for adding power and cfm.  I don't think they are known for fuel economy.

Gnarls.

[sirdeuce]

I've modded the stocker (live in Cali) and gotten good power from it. If you can find someone to do it the throttle plates can be enlarged and the venturis resized. The secondary can be removed and machined on a lathe, the primary has to be done in the carb body. Jetting is available in enough sizes. Air jets and emulsion tubes the same. Drill fuel ports and blend intermediate circuit..... Many hours of work to get a decent increase in airflow and proper fuel mix. Probably got as much as a Weber 32/36 and looked completely stock in the process. Passed smog too!

A well tuned Weber can get good economy.

[Gnarly4X]

I've modded the stocker (live in Cali) and gotten good power from it. If you can find someone to do it the throttle plates can be enlarged and the venturis resized. The secondary can be removed and machined on a lathe, the primary has to be done in the carb body. Jetting is available in enough sizes. Air jets and emulsion tubes the same. Drill fuel ports and blend intermediate circuit..... Many hours of work to get a decent increase in airflow and proper fuel mix. Probably got as much as a Weber 32/36 and looked completely stock in the process. Passed smog too!

A well tuned Weber can get good economy.

Holy hotCaCA Batman!!!

Why not just buy a bigger carb!!

Actual gas mileage has ALWAYS had more to do with the right foot!

Gnarls.

[sirdeuce]

Holy hotCaCA Batman!!!

Why not just buy a bigger carb!!

Actual gas mileage has ALWAYS had more to do with the right foot!

Gnarls.

Living in California has it's drawbacks. The smog Nazis don't like non OEM paraphernalia. A 20R bore stroked, bored and ported with late model 4-2-1 exhaust and a modified carb and mild cam would pass visual, and if tuned properly would pass smog. Ya had to get creative back then. I had several Celicas running my engines in the San Joaquin Valley. They weren't as fast as dual carbed, headered massively cammed screamers, but they would surely surprise you.

I do miss those days. (Sigh)

[opus [OP]]

Can I snip this wire?  I've never hooked anything to this port before.

[airkewled]

Looks like your electric choke.

[opus [OP]]

Its the bowl vent I believe.