idle question

[transalpian]

greetings!

I have a strange (to me) idle situation.

When first starting the truck in the morning, it idles great! Smooth and even.

After about 15-20 seconds however, the idle gets rough. It will continue to run, but nowhere near as smooth as at first. Off idle, it "seems" to run fine.

I had a sticking float needle valve issue a few weeks back that prevented the truck from running at all (stuck shut). At that time, I took the top of the carb off and blew air (and carb cleaner) through all the jets and passages. Thinking back, that was the time when the current problem surfaced, before that she idled like a kitten (according to my 10 year old).

I chased the stuck float valve issue for a while before I found it. The main "other" thing that I did was to replace the plugs and check the plug wires because I really thought it was ignition related. I pulled the dizzy cap off (to look for cracks, etc) but didn't change the timing or even really look at the points.

I'm almost convinced my current issue is fuel related, but where should I look?

[transalpian]

Got a theory I need to check out.

Can someone post (or point me to) a picture of a good float needle valve? Particularly the shape of the needle tip.

[transalpian]

Here's what I'm thinking, I'd like your opinions.

When the truck sits, some fuel evaporates from the float bowl. When this happens, the fuel returns to the correct level, allowing nice idling at the first start-up. So I am guessing a high float level, caused by a sinking float (possible), mis-adjusted float level (less likely, since it ran good before), or a worn float needle and/or seat (!!!). Since I had the issue with the float needle sticking shut, I tend to think the worn needle and/or seat is the most probable cause.

Agree? Disagree? Other thoughts?

I'll probably pull it apart tomorrow and adjust the float level to see if this helps. Might as well check that the float "floats" while I'm at it!

[giftshopduane]

If your theory was correct as far as evaporation goes, the fuel pump will quickly fill the bowl up upon cranking. Is it choked? Electric, manual? Is there supposed to be a phenolic spacer under carb? If so is it there? There are a few other factors that could be at play. You are seeing a funky idle after it warms up. Could be electrical. But judging by the fact that you noticed it after you cleaned your carb probably not. Did you play with the air mix after cleaning? You could have been running fact with a clogged passage, now clean carbs leaned out a bit, or vice versa. Double check the float height, dial in your air mix, check timing, clean points, cap and rotor, clean your grounds easy basics. Air mix is my guess.... (turn air mix screw in until eng stumbles, then back it out until it runs its smoothest with no noticeable gains in idle with further turns, then back in 1/4 turn should be fine there are close enough, adjust further if necessary. Try it a few times to get it right. 1/8 turn at a time). Blip the throttle and see how it idles from there. Carbs are funny things sometimes.

[westcoastkevin]

It is probably fuel related but....... is your coil getting hot. Just on the wild chance it is going out?

[transalpian]

Found the issue over the weekend.

Lowered the float level and the idle smoothed out greatly. Futher leaned out the idle mixture and lowered the idle setting slightly too. Back to "running like a kitten"!

All better now!