Carb trouble after adjustment

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socalcorvair63
Posts: 3
Joined: Fri Sep 08, 2017 10:26 pm

Carb trouble after adjustment

Unread post by socalcorvair63 » Sat Sep 09, 2017 5:23 pm

Hello everyone,
Im having a carb problem with my 63 monza coupe. I was syncing and tuning the carbs, and after adjusting the mixture screws to the 1 1/2 turns out from seated that I have told is the best place to start when adjusting them, the passenger side carb stopped responding to mixture screw input. If I ran in the mixture screw in on the drivers side slowly, it would start to stumble as it became too lean, and then I would adjust until the vacuum peaked. On the passengers side, you could adjust the screw from seat to almost completely backed out with no response at all, except for a small surge of rpm (maybe 20-30) as you backed it out a little past seated. I zeroed the carb linkage to the best of my ability, and both of the air valves are just cracked open (1 1/2 turns from first contact with the throttle plate,) not sure if any of that could potentially cause this issue. it still idles, but the right side carb doesn't seem to be supplying any fuel besides the accelerator pump, due to it bogging hard when you open the passenger carb only, the lack of power, the cold head temp (175 degrees after 10 minutes of idling for adjustments) and the fact that the dead cylinders would come alive if you sprayed some crb cleaner in when opening the air valve. The carb in question is freshly rebuilt by a reputable corvair shop, the working one is the factory carb ironically. I'm not sure if I bottomed out the mixture screw too hard accidentally and punched out the bottom of the seat (although I don't believe i was too rough with it and the needle looks fine) or if I just did that bad of a job adjusting it, or if i'm missing something entirely. The car did run ok before, minus some surges and bogs when accelerating. Sorry to ramble on for so long, but I just felt that giving the most information would aid in diagnosing the problem. Any advice from the guys that know what they're talking about when it comes to these cars (not me) would be appreciated.

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cnicol
Posts: 450
Joined: Wed Jan 20, 2010 8:11 pm

Re: Carb trouble after adjustment

Unread post by cnicol » Sat Sep 09, 2017 6:04 pm

It sounds like the idle jet may be plugged. (It's a really small orifice). Sometimes you can unplug it by: Remove the mixture screw, blow a little toot of compressed air into the idle mixture screw hole. (Guard your eyes, fuel sprays up out of the air horn). This process will usually clear the jet. If not, you may have to remove the venturi cluster and poke a tiny wire through. You should be able to see daylight through the jet if you hold it up and look through.
carburetor venturi cluster.jpg
carburetor venturi cluster.jpg (10.53 KiB) Viewed 135 times
'61 140 PG Rampside
'66 Rear Alum V8 4-dr
'60 Monza PG coupe (sold, sniff, sniff)
'66 Corsa Fitch Sprint Conv. (First car 1971, recently repurchased)

socalcorvair63
Posts: 3
Joined: Fri Sep 08, 2017 10:26 pm

Re: Carb trouble after adjustment

Unread post by socalcorvair63 » Sat Sep 09, 2017 7:34 pm

cnicol wrote:
Sat Sep 09, 2017 6:04 pm
It sounds like the idle jet may be plugged. (It's a really small orifice). Sometimes you can unplug it by: Remove the mixture screw, blow a little toot of compressed air into the idle mixture screw hole. (Guard your eyes, fuel sprays up out of the air horn). This process will usually clear the jet. If not, you may have to remove the venturi cluster and poke a tiny wire through. You should be able to see daylight through the jet if you hold it up and look through.
carburetor venturi cluster.jpg

you were dead on. I assumed the carb wasn't plugged up due to the fact that it was "rebuilt" a week ago by a corvair only shop, but when i pulled the top of the carb off, there was visible debris plugging the main jet and the accelerator pump well was full of sediment and debris, as was the rest of the bowls. Simple problem with a simple fix caused by a simple man overthinking it all.

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