Air screw

casamere · Post by **casamere** » Sat Jan 27, 2018 4:32 pm

Am I right in unscrewing the air screw 1 1/2 turns on CA77 carb. Thanks.

jkv357 · Post by **jkv357** » Sat Jan 27, 2018 7:55 pm

That's typically the starting point.

After the engine is fully warm, adjust the idle mixture screw to achieve the highest idle speed, then go richer ("in" if the screw is an air-bleed, "out" if it's a fuel-bleed) until you hear the RPMs just start to drop.

The idle mixture adjustment on the CA's carb is an air-bleed - so you would want to turn it "in" slightly after reaching the maximum idle speed.

Then adjust the idle back to the proper speed with the idle speed screw.

casamere · Post by **casamere** » Mon Jan 29, 2018 9:39 am

jkv357 wrote:That's typically the starting point.

After the engine is fully warm, adjust the idle mixture screw to achieve the highest idle speed, then go richer ("in" if the screw is an air-bleed, "out" if it's a fuel-bleed) until you hear the RPMs just start to drop.

The idle mixture adjustment on the CA's carb is an air-bleed - so you would want to turn it "in" slightly after reaching the maximum idle speed.

Then adjust the idle back to the proper speed with the idle speed screw.

Thank you.

jkv357 · Post by **jkv357** » Mon Jan 29, 2018 10:02 am

You will most likely be pretty close with 1.5 turns out, but the optimum setting will change with fuel type/octane/seasonal blend, air temperature, etc.

If you notice the idle is lower than usual, that can mean it's time to make a slight adjustment to get it back to the optimum setting.

As temps drop you will need to richen the mixture and vise versa.

casamere · Post by **casamere** » Mon Jan 29, 2018 10:32 am

Should only need one setting as it doesn't go anywhere once the temp drops below 20c.