Time for 'Idle' Gossip

[GregH]

Need some insight into trying to get the engine to idle better and understanding the process better as well. I have read over many of the topics here about idle and have tried variations of them all at one time or another.

- Currently has the Indigo EI installed
- Idle valve is the typical 1-1/2 turns from closed
- Choke fully closes and fully opens
- Throttle idle screw is set for as low as I can without it stalling out

-I have tried various settings on the idle air screw without much change. With the choke on it always starts within a few seconds which indicates to me too rich. At one point had the screw over 2 turns out and still started very easily first try.

- Plugs are always black and sooty but don't look wet or smell of gas though I do get that sheen on the water from the exhaust.

- With choke on idles lowest about 1100 rpm. When to open the choke the engine rpm increases by 100-200

- My carb is a 4 bolt without an adjustable main jet. and has been cleaned several times.

- while idle has tried to adjust the dist to get it as low as possible and smooth which means abut 1100 rpm. The advance is smooth and springs back nicely with fresh springs

I know I am missing some basic understanding or something to be able to get this solved.

Thanks ahead of time!

[sastanley]

Greg,
Do you have the Indigo PCV system installed? It worked great to suck in the crankcase oil, however, I could not get it to idle very well with it installed...now I just move the blower hose up from the bilge floor after starting, up near the oil fill (I have a K&N breather filter on there), and let it suck the fumes out the blower..Once the engine is good and hot, the blowby seems to diminish to almost indiscernible.

[Tim]

When was the last time you cleaned the carb? If the idle jet is clogged, the engine will start and run above idle speed, but will not idle below around 1100 rpm.

[Dave Neptune]

Sounds to me like you may have the float set way to high. I always found my engine to run and idle better with the float set about 1/16" lower than stock. I also used the Indigo PCV system and idled at 700, 600 in gear and never an issue.

Are you using the stock heat range plugs? Colder plugs will show much more color and can be easily fouled if your adj jet is set to rich or again a to high float level.

It could also be a clogged air jet which will really richen things up or even a weak ignition including timing. A clogged idle air jet would only influence below 11-1200 RPM or slower as by then the carb is running on the hi-speed circuit and that air jet is in the center of the float bowl and is very much influenced by float level. It supplies air to the fuel through the emulsion well which is fed by the main jet.

Dave Neptune

[ndutton]

Don't discount the effect or proper timing on idle speed. It matters.

[capnward]

+1 on what Tim said. The idle jet can be even partly clogged and inhibit idling. Every spring I remove it and run a wire from a wire brush around in it, as Don Moyer demonstrates in his video. The clog may be too small to see. Blowing stuff through it won't work.
I currently idle at 800 in gear and 1100 in neutral. I have been meaning to adjust the throttle lever stop screw to try to get it to idle lower, but what I do not want is for it to stall when put in gear at idle. When the engine is nice and warm, idle in neutral goes up in RPM. I don't think of that as a big problem. I do not turn the distributor (timing) to get low RPM in idle, but to get high RPM in gear at cruising speed. If that makes the idle speed high, so be it.
I have the Indigo PCV thing, but it doesn't' seem to hurt the idle. I don't know if it makes the engine run leaner because of crankcase air directed into the combustion or richer because of the crankcase oil in that air, but I would rather not have crankcase oil running into the carb, as in the original configuration. My blower hose is near the carb. Gas fumes are the ones that concern me.
You say the idle screw, or valve, is 1 1/2 turns from the seat, as is mine, but you also say you "set for as low as I can without it stalling out.". Turning it down (in) makes it richer, because that decreases the air intake. That would explain the sooty plugs and sheen on the water. I have read on this forum that you turn the idle screw out, making it leaner, until it begins to lose RPM. To me that is setting the idle screw higher, not lower.
I try to run with the choke on as little as possible to avoid rough running, sooty plugs and soot on the water. It starts on the first try with choke on but doesn't run smoothly until choke has been open for a while. If engine is warm, it doesn't need the choke to start. If it is cold the choke should remain closed for at least a few seconds after starting or it may shut down. The engine smooths out and gains RPM as it warms up, but that is no problem to me.

[GregH]

Originally Posted by sastanley

Greg,
Do you have the Indigo PCV system installed? It worked great to suck in the crankcase oil, however, I could not get it to idle very well with it installed...now I just move the blower hose up from the bilge floor after starting, up near the oil fill (I have a K&N breather filter on there), and let it suck the fumes out the blower..Once the engine is good and hot, the blowby seems to diminish to almost indiscernible.

I do have it installed, though I rebuilt the engine over winter of 21/22. Once upon a time it did idle nicely at about 700-800, but something changed last year ...

[GregH]

Originally Posted by ndutton

Don't discount the effect or proper timing on idle speed. It matters.

I was planning this weekend to pull the dizzy and double check I have it set at #1 TDC. Then once dizzy installed back, run and point timing light at it.

For idle on the roll pin (yeah I know it's not precise) the timing light needs to be set at 17 degrees?

[Dave Neptune]

Total timing of 34 degrees. Idle around 0~4 degrees is fine.

Dave Neptune