Star wheel adjustment

Hornet2008 · #1 05-04-2018, 04:17 PM

Hi All,
My IO 320 D1A idles roughly and there is no rise in RPM moving to idle cut off. This, and black smoke on start, indicate it is running too rich idles at 700 RPM once warmed. I've read on carbs engines the mixture adjustment needle is turned out one to one and a half turns in most cases from closed. I have moved the star wheel in the lean direction a number of clicks (10) and still have rough idle and no rise. Do I need to make several turns as opposed to moving it clicks. Anyone able to give me a starting distance between the two blocks where the star wheel is positioned.

Walt · #2 05-04-2018, 06:10 PM

Nominal setting:

Hornet2008 · #3 05-05-2018, 02:12 AM

Thanks Walt, much appreciated. Can I ask where Fig 5 is found?

Silver Hawk · #4 05-23-2018, 01:23 PM

Hi Pete, try looking at the 15-338 manual here for idle adjustment and 15-810 for the nominal length for the link to start with:

http://www.precisionairmotive.com/servpubs.htm

If it is rich, you should be getting a big rise, no rise indicates lean.

Rupester · #5 05-25-2018, 07:28 AM

I had exactly the same problem when I first started mine. I was amazed at how much adjustment it took to get the idle condition properly leaned. I also quickly learned that all taxi and ground ops must be done in full lean condition, otherwise it will foul plugs quite quickly.

Walt · #6 05-25-2018, 07:54 AM

Quote:

Originally Posted by Rupester

I had exactly the same problem when I first started mine. I was amazed at how much adjustment it took to get the idle condition properly leaned. I also quickly learned that all taxi and ground ops must be done in full lean condition, otherwise it will foul plugs quite quickly.

A properly adj FI system does not need to be leaned on the ground.

Rupester · #7 05-25-2018, 11:45 AM

Quote:

Originally Posted by Walt

A properly adj FI system does not need to be leaned on the ground.

So are you saying you wouldn't accept a 40RPM idle increase between normal rich and full lean?

Walt · #8 05-25-2018, 12:33 PM

Quote:

Originally Posted by Rupester

So are you saying you wouldn't accept a 40RPM idle increase between normal rich and full lean?

If you have less than approx 50 rpm rise you should not be lead fouling plugs on the ground, so further leaning will have almost no effect at that point. If you're loading the plugs up with lead I would suspect you are doing that while flying not on the ground.