Carb Question

Joined
Feb 28, 2022
Messages
62
Location
Austin, TX
1973 FJ40. Stock F155 and factory 3 speed. factory Asian double barrel carb.

the pic below isn't the carb I have, but I'd love to know the purpose of the highlighted arm and if that rod connection to the swivel piece should be connected to the end of the swivel and/or locked in place wherever it sits?
1662768039280.png


Mine is pictured below. My arm isn't actually connected to anything. The lock washer / pin is gone so it just sits free. And it always finds itself stuck underneath the swivel.
1662768082666.png


What is the purpose of this arm? I can get a washer / pin to get it connected ... but does it lock into the spot I put it? I assume so otherwise it would just slide around and do nothing. If I lock it in place, is there a 'right' place to lock it?

Thanks! Apologies for the dumb questions. FYI the truck runs great WHEN WARM around the neighborhood. Hesitates and backfires out of the exhaust under load >= 2800k RPMs in 2nd and 3rd. It definitely hesitates and bucks until warm. Timing is set. Compression is good. I fixed a vacuum leak and it's consistent around 17 idling. I've tuned the carb per the manual. I think/hope this is a final piece of the puzzle and plan on getting it attached tomorrow.
 
Joined
Jul 5, 2005
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Ames, IA
That's the carb choke breaker linkage. Yours looks correct, but probably needs the washer and pin to hold it in behind the "smiley face groove".

The purpose is to open the choke slightly on full choke cold start. it doesnt hold it tight, it's meant to travel along that groove depending on how much choke is pulled.

Looks like your choke wire needs adjusting too.
 
Last edited:

Pighead

Stop calling it an FJ
Joined
Aug 31, 2004
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9,193
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Camino
That's the carb choke breaker linkage.
I always thought that was called the throttle positioner, and somehow slowed the closing of the throttle when you took your foot off the skinny pedal.
Obviously, i don't understand it and i fear what i don't understand. So i just took mine off. Probably didn't work anyway.
Looks better without it too.

20220910_125932.jpg


20220910_125940.jpg
 
Joined
Feb 28, 2022
Messages
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Location
Austin, TX
Thank all - I'm going to see if I can find some small washer and pins to hold it in place. I was hoping this would help with my stutter / hesitation under load around the 2800 - 3k RPM mark, but it sounds like it is more geared towards the cold start / choke.
 

Pighead

Stop calling it an FJ
Joined
Aug 31, 2004
Messages
9,193
Location
Camino
Thank all - I'm going to see if I can find some small washer and pins to hold it in place. I was hoping this would help with my stutter / hesitation under load around the 2800 - 3k RPM mark, but it sounds like it is more geared towards the cold start / choke.
1) those small washers and pins often come in a carb rebuild kit, which you should always have one or two on hand.
B) hesitation/stutter under load at 2800-3k rpm would make me think fuel delivery (starvation) problem maybe...or timing(needs more advance?)
III) i never tach mine that high until the engine is fully warmed and choke is in.
 
Joined
Feb 28, 2022
Messages
62
Location
Austin, TX
1) those small washers and pins often come in a carb rebuild kit, which you should always have one or two on hand.
B) hesitation/stutter under load at 2800-3k rpm would make me think fuel delivery (starvation) problem maybe...or timing(needs more advance?)
III) i never tach mine that high until the engine is fully warmed and choke is in.
Thanks for the tip - I replaced the fuel filter last night and it made an immediate improvement. It took quite an effort to blow through the filter I removed from the truck. I take that as a sign that it's clogged and needed to be replaced. No more hesitation while cool and I was able to get up to 4k RPMs in 1st, which I doubt I've done yet. I'll put some more miles on today. The bad news ... I got a filter where I could see the fuel flowing through, and it looks like the color of a penny - fuel color or rust? Whack-a-mole, but hopefully I'll know if I'm good for a bit and the filter gets clogged again.
 
Joined
Feb 28, 2022
Messages
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Austin, TX
a few highway miles and some climbs - no more hesitation. Fuel filter for the win! However, I do think I have some sediment in the filter visible after only a few miles - so it's doing it's job but no wonder the old filter is plugged. I'll snap a few pics when I get a chance. Onto more research.
Thanks -- Dave
 
Joined
Feb 28, 2022
Messages
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Location
Austin, TX
Here we are after about 15 miles to/from work and around the neighborhood ... I assume this isn't good (??? :)), and I am going to order some more filters to keep swapping and start looking at a new tank or some way to properly clean it. I leave town so the truck will sit for a bit but I'll post some pics later when I swap this and empty this filter.

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