Toyota (Aisan) Sock Carburetor Rebuild

10/19/12 - Tearing the carb apart for a rebuild to try and clear up the stumble on acceleration. I guess something always needs go wrong. Woofed up one of my main jets with an ill chosen screwdriver. Didn't think I was going to get it out for a while. Ground down a big, nice Snap-on screwdriver I've had for years because the fit was perfect - and it worked. I guess I have a special "jet" screwdriver now.

Carburator on bench

Reusing this jet (the hole is good)and a replacement does not seem available at Toyota, SOR, etc.

Snap-on socket

Looks like a small 1/4" drive, 9mm Snapon socket works (maybe a little deeper than most?) for the hard to reach Power Valve. A deeper socket is probably a better call.

Snap-on socket

Two strange things about my venturis:

  1. Were not "rattle" loose but not very tight either...
  2. Both were "double" (with the number 1) and appear to be the same (no triple)?

Everything looks original - no messed up screws, etc.? Later found out the FSM was written for 1975 2F, which has single ring and double ring boosters.

Top view

From Jim C...
FSM was written for 1975 2F, which has single ring and double ring boosters. 77-later carbs are double/double. There are differences in the emulsion tube and air jet, so try to keep the boosters in the correct hole.

If the hole is still correctly sized, then the jet is good. Use a dremel or hacksaw to
make a new slot 90* to the original slot. Free advice: the stock 1.36 jet size is way too lean. Try drilling to 1.45 or 1.50.

If you can smell the exhaust it is because it is too lean, and you can smell half burnt HC. Slightly rich exhaust doesn't smell bad, because it is low in HC and
high in CO, which is odorless. The 1.36 was slightly too lean in 1978 with real leaded gas. 35 years later, the gasoline at the pump is significantly different. The additional alcohol and MTBE make the fuel "leaner", so the carb jets need bumped up to compensate.


I actually found a .055 inch reamer in my old stuff which seemed to do nice job on the jet so I should be around 1.40 mm now - I'll see if I can find something a bit bigger/closer to the 1.45 or 1.50.

10-29-12 - Got the carb back in and had a short test run with the idle/air mix screw just set at the 1 and 1/2 turns out. All the stumble from idle to higher rpm is gone and driving along in gear I no longer get the on/off the gas pedal "jerk" of the engine trying to get the RPMs up.

Opened up the main jet to 1.50 (thanks again Jim C) and not only does it seem to run better - I think maybe it smells less. Need more time to test adjust.

And now I have a few new SST carb tools, special jet screwdriver and a chopped off 12mm open-end. Never found new jets for sale, and ended up with 2 rebuild kits - a Keyster kit from Kurt at Cruiser Outfitters . Then of course the secondary was bad. Kurt didn't have one in stock, Napa ordered an alternative instead of the correct Hygrade number I gave them. Finally got the Hygrade (older one I think - had copper washers, etc.) so now I have a few spare parts.

Reamers and Screwdriver

11-07-12 - The Carburetor was great for a while. Then I left a store in San Mateo to drive home a few days ago and started getting sputtering and bad "off-idle" again. Got home and stuck a tach on the hot engine and the idle was low so I set it back to 650 and adjusted the idle/air intake screw again. Ran better and the next few short trips seemed ok but wasn't running like it was when I first put the carb back on. Went to vote yesterday with the added bonus of finding some dirt to drive/park on (behind the local Fire/Poll station). On the way home started to sputter again - dirty gas like. Took a closer look at the carb and the accelerator pump was completely locked up.

Election day

Pulled the carb again and found the accelerator pump, pump outlet and ball all working fine - but the spray jet (just the small hole itself) was completely clogged with a very small chunk of gunk (technical term ). With the good seal/pressure the pump could not push gas out the jet. Very gently took the smallest drill rod I could find, loosened up the gunk in the hole and blew out a little splatter of brown grunge. This after the carb body had earlier been dipped, sprayed out repeatedly with air, carb cleaner sprayed through all passages (that same jet a number of times), etc. Everything else in the carb still looked spotless (new gas line filter put on earlier).

From Sarge:
If you have rubber fuel line anywhere , that could be the culprit . This ethanol crap is eating fuel lines very rapidly , breaking them down from the inside out . I've switched everything I work on to a new blue line that is being used in atvs, sleds , ect . It's available in rolls from Harley dealers nationwide in their aftermarket book.... I'm a huge fan of putting a decent filter just ahead of the carb , doing just that tomorrow when I install THC's new carb now that the dumb exhaust is done ....

More from Jim C:
RFG is also causing rubber diaphragms in fuel pumps to crack & crumble, sending tiny shards of trash directly to the carb. Only fix is to keep the carb inlet screen intact, but that just leads to the screen being restricted, which still requires air horn disassembly to properly clean.


Only thing I can figure is a small piece of gunk was left hidden somewhere (like the base of the pump around the ball, etc. where I cleaned out a lot of stuff earlier) and later worked it's way up to the jet after a few days. Now everything is back on the truck and the pump is delivering a strong shot of gas from the pump jet. The truck runs well again.


Third Time’s A Charm?

Then, later (11-23-12) ... more fuel delivery problems. The truck had been running great. Filled the tank yesterday and had a conversation with 2 guys from San Salvador in a nice jeep - they were very interested in the 40 - said they were common back home. Started back feeling good - short run on 101 at about 67 mph (iPhone speedo). When I pulled off the freeway I heard what sounded like maybe a backfire or two and then at 30-35 mph the engine started to miss - kind of like big "flat" spots of no gas. Stopped and looked around the engine, etc. Pulling the choke off and on helped me manage to limp it back home. Happy Thanksgiving

Pulled the air cleaner this AM and can't see anything around the carb. Seems to idle fine but any gas and you get one normal-like rev and then it dies. If I pull the choke and turn the key it starts and revs up and then just dies. Do it any number of times and it continues to start - and then just dies. I'm thinking maybe the fuel pump (which I think is probably 30+ year old original) is my next adventure? Also wondering about the old worn rubber/new gas in the pump that came up earlier, etc. Don't think it's the pump - the glass level seems to maintain a dot-level amount of gas...
Another question/possibility... maybe the main nozzle fuel circuit of the carb primary is now plugged with the same weird stuff that got in the accelerator jet?

Note: ICS makes "Click" sound when carb connector is plugged/unplugged w/ KOEO

From Jim C.:
Yes, if the fuel level is on the sight glass, then there is enough fuel in the bowl for the carb to function.
Sounds like the problem is internal to the carb, or some kind of ignition failure.


I really appreciate all the good experience I'm getting removing/installing the carb. Can't see anything at this point. Seems to me like maybe the accelerator pump (working well now) supplies some gas and that's the squirt the engine runs on until it dies. Need to pick up a can of spray carb cleaner.

Third time on bench

Don't know if this could cause the current problem but it can't be good. This O ring looked OK and I didn't change it (live and learn). Kind of dumb considering it could be 30+ years old. At least I've found something.

broken rubber seal

Can't find blockage anywhere else with the carb spray. Replaced the Power valve with a new one from the Hygrade kit (even though it has a plastic part ) just for heck of it.

Put the carb back in with a static 1-1/2 turns out on the Idle mixture adjusting screw. Seems to start and run just fine (idle needs adjusting). So it must be that torn O ring in the Solenoid Valve? Strange that little rubber part made the truck nonoperational. I did put another Power Valve in but the original looked OK.

carb back on

A short run right after the carb went on with no adjustment/hot tuneup and all is good!

Bird Publishing © 2014