From what I've researched the mixture screw (from the factory) can vary from 1-1/8 turn to 1-3/4 turn out from seated. A lot of guys that rebuild carbs set the mixture screw at 2 turns out. fwiw

 

Thanks for that, it will be interesting to see what answers I get as I made up a separate topic for that.

I started thinking about my issue and then started looking at the carb, pushing the slide up by hand and looking at the throttle plate. I wondered if my problem wasn't related to the throttle plate not closing enough at idle. There are several small holes on the floor of the carb and only one of them is controlled by the mixture screw, the rest add extra fuel just as the bike goes off idle. These all receive their fuel from the pilot screw. If the throttle plate isn't closed enough to block these other holes, no amount of fiddling with the mixture screw will allow you to set a proper idle. So I figured what the heck. I got the book out and adjusted the pull cable until it reached its stop. Then I backed off the idle cable and using a small piece of paper between the screw and its stop, made sure the throttle plate was completely closed and yet opened fully to its stop when the throttle was turned as far as it would go. It seemed to me that the idle cable hadn't been adjusted properly to allow enough slack so that the throttle plate could close.
So I initially set the idle screw at one turn out and tried to start the engine. No go, so I added the choke and it started ( a good sign ), kept the bike running by turning the throttle grip, then I had to adjust the idle screw a bit more to get the bike to idle. I did some preliminary adjusting of the fuel mixture screw somewhere in the range of 1 1/4 - 1 1/2 turns out and the idle at 1000. I shut the bike off and it would have to wait for a ride.
Sometime later in the day I took the bike for a short ride. To get it to start I had to again use the choke ( yes a good sign ) and was able to ride the bike away on part choke with no burping/surging from a rich/lean condition. Another plus. During my ride I made one stop and turned the mixture screw out about 1/4 turn and reset the idle to 1000 rpm. Initial findings are that I'm on the right track and need to fine tune the mixture screw. Engine ran fine and seemed to react better to the throttle, both rolling on and off the throttle. I was low on gas and then the gauge fuse blew, so it was time to go home and deal with that gremlin. The joys of a 24 yr old bike.
I bought the bike used and others had been in the carb before me, but I should have twigged to the throttle plate issue as I always found it strange that both the idle and throttle cable had just about the same number of turns out at the adjuster, up near the throttle. Also its an easy fix to just turn the idle screw up to cover jetting issues. HD also has a real different way of setting up their cables ( small spring on the idle cable ) that I'd never seen on either Japanese or BMW bikes that I'd owned. It appears to me that small spring is there to help control slack and its somewhat critical to get it set right. Most bikes with two cables are a push/pull design and they don't work the way HD's do. So I'll play with the mixture/idle screws a bit more and hope for the best.

 

You will always have one of the low ports (tiny 4 holes) partially uncovered by the throttle plate. The idle speed will be too low otherwise from lack or air intake. That's why and how the low jet affects idle mixture to some slight degree.

Always best to get one running and idling then go ride until the engine is totally up to temp before trying to trim the mixture screw. And that doesn't mean "around the block," more like 20 - 30 miles.

My particular bike, you cannot adjust the cables "by the book" because if adjusted at WOT and the cable crank touching the stop, it will never return to idle without the return cable being so tight, there's zero return of the throttle grip without effort.
I adjust the pull cable to zero free play, then the return cable to "just" where the grip will return on it's own, leaving it loose by the book and the stop on the carb has about 1/16" gap. Just where it works out...

 

Thanks. I agree with getting bike up to temps and my normal carb tuning method is to ride for about 15 minutes, stop check idle, adjust mixture screw/idle, then ride again until i a get a good steady idle of 1000 rpm on the bikes tack. I agree there has to be some slack in the idle cable, otherwise the throttle plate won't close and you stand the chance of breaking a cable. So once you have the pull cable adjusted properly thereafter one should only have to deal with the idle cable to set the free play of the throttle. That way you can actually vary the idle by its screw if you need to.

 

Sounds like you about got a good smooth idle going for you. Once that's established it's time to start reading the spark plugs and listening for accel/decel signs to adjust jetting properly

 

Well on my bike at my altitude, 1 1/4 turns out of the mixture screw works about the best. This is for a stock engine, exhaust, intake etc, jetting stock ( 42/175 ) but with a CVP needle. This is on a fully warmed up engine.

 

Further update. I replaced the CVP needle with the stock needle. The CVP needle is noticeably shorter than the stock needle, so it adds more gas earlier. I had noticed that my gas mileage had dropped a bit and a bit of richness on the spark plugs. So seeing as the rest of the bike is stock I went back to the stock needle. I've ended up at about 2 1/2 to 2 5/8 turn out on the mixture screw. Bike runs fine at my altitude. I'm also trying a set of standard NGK plugs. We have no local HD dealer here anymore, as HD shut them down during the last go around, so it is a pain to get even basic maintenance parts as nearest dealer is 2 hours away. Shipping costs are crazy up here.

 

I finally got some parts in from CV Performance mainly some gaskets, a new slide and a Sportster needle. On checking it turns out I already had the Sportster needle in the carb, checked with a caliper. Others had been in the carb before me so I really didn't have any idea what I had.

I had suspicions that my existing slide had been drilled out, and on checking the vacuum hole, it was larger than on the new slide. The old slide seemed lighter. I installed the new slide and needle and started the bike. After it warmed up the idle was noticeably slow, so I had to adjust the idle. I left the mixture screw alone and will wait for a ride to see if it needs adjusting. I went out for a ride yesterday. The bike starts better and the idle is noticeably more stable and ran fine throughout the rpm range to cruising speed. It's hard to explain but the engine ran smoother and playing with the throttle, slight roll off and on was more precise. The downside if any, ( hard to tell from the seat ) was that the bike didn't seem to accelerate quite as quickly. It accelerated smoother and had good pickup, just different from before. Its a stock engine so they never did have a lot of power. The new slide appears to be metering the fuel flow more consistently.

So all along the drilled slide was causing my issues. I can only guess that being lighter and the larger vacuum hole, resulted in the slide reacting quicker to vacuum changes, even at idle and in some cases over reacting. There are two camps on slide, drill don't drill. I guess it depends on what you want out of your bike. So it seems I'm in the Joe Minton camp, don't drill the slide.

 

Further update. On all the reading and trial and error on this bike as well as previous experience on carb'd bikes I think I've finally figured it out. Some things take me a while, and I go until I fully understand what is happening. Also take into consideration that I'm using the Eze Screw adjuster and the length and taper at the end is a bit different that the stock mixture screw, which likely has an affect on how many turns in or out I end up with, compared to the stock mixture screw. The mixture screw only affects idle and has minimal affect anywhere else. I've never been one to just follow somebodies blanket recommendation when it comes to carb tuning. There are too many variables to make it that simple. Each engine is going to have its own sweet spot.

Everything I've read on carb's it basically says that your fuel mixture screw should be between 1 - 3 turns out. If it is under 2 turns, then your pilot jet is too rich, if it is over 3 turns then your pilot is too lean. You want to adjust your idle so that you get the smoothest idle, with no backfiring etc on roll off. Also the rpm's should drop quickly to the recommended idle speed. If it hangs that's a problem and if it dips below the idle speed then that's also a problem. Turing the mixture screw out ( more fuel ) if it hangs, and in ( less fuel ) if it dips.

The one thing that I've not heard much talk about is the altitude's affect on the pilot jet, which in turn affects the idle circuit, as it supplies the fuel to that circuit. So in my situation with a stock bike, stock jetting, air filter & exhaust stock and living at an altitude of approx 2700 feet my pilot jet is already too rich and if I was being really critical I should have a 41 pilot jet. I know that sounds dumb but if you run a web based jetting program based on your living and riding altitude it will give you the proper jet sizes based on your elevation. So I was out riding today and my Eze mixture screw started out at about 2 1/2 turns out. Bike started fine, but doesn't really like to idle with much choke on a cold start. ( An indications that it is too rich ) Off I go and slowly push the choke off, no drama, bucking etc. My first stop of highway driving about 10 miles away, I stop and bike is idling OK, but since I'm doing a test with the new carb parts, I turn the mixture screw in about 1/2 a turn. No real change in idle, bike pulls away fine, so I go about another 10-15 miles and stop again. This time I turn the screw in another 1/2 a turn, so now I'm about 1 1/2 turns out on the mixture screw, Idle is still good, good acceleration and engine seems happy. Again I go for a few miles and pull over. I've a slight hang on the idle, so I turn the mixture screw out 1/4 of a turn. Continue on my ride and get back into the city and stop. I put the mixture screw back to 1 1/2 turns and adjusted the idle screw a touch to get a 1000 rpm idle. That on this day is where the bike runs the best, with no decel popping or hesitations of any kind. It has very good throttle response, runs smooth at any throttle setting. So through all of this I've found that the bike appears to like the 1 1/2 setting on the Eze Screw on this day ( temps & humidity - carbs are always affected by these and one day it runs good and the next it will be a bit off ). So at the end I've found that my pilot jet is too rich. But I'm not going to change it out as there is no real reason to do so as the idle is good and the bike pulls fine off idle. Who knows someday I may be at sea level.

So I'm about 1/4 turn richer than the stock setting of 1 1/8 - 1 1/4, which is pretty normal on a stock carb/bike as they need to be slightly richer than the factory spec, but not a lot. Enough for now.

 

I re read this post and found that I'd made an error and it was too late to edit. My mixture screw is actually set at approx. 1 1/4 turns out, not 1 1/2. I'll be interested in seeing if this setting stays workable. I'm pretty sure on the stock mixture screw it would be out further, just because the Eze Screw has a bit of a different tip end. So I'm thinking I'm actually a bit further out, if I was using the stock screw. All I care about is that it runs good, both cold & hot.