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General Category >> Rubber Side Down! >> Turn in or out to "lean" some?
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Message started by Oldfeller2 on 09/03/06 at 06:01:15

Title: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/03/06 at 06:01:15

Do you turn the air screw (the one under the plug) in or out to lean it some?

I am running slightly rich (mild gold pipe) and I want to lean it a bit at a time with a week at each partial turn setting until I find optimum for my particular bike.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by Dynobob on 09/03/06 at 06:05:22

IN (clockwise) is leaner.

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/03/06 at 07:06:04

Conditions at start of experiment -- Stock bike, 2002 year LS model at 4,000 miles. Half spacer and uncapping air screw mods performed at 1,700 miles, highest idle speed discovered at 2 1/4 turns out and idle adjusted to circa 1,000 rpm as per general list recomendations.

Top speed 87 miles per hour, gas mileage runs between 46 and 52 mpg. Pipe runs a mild gold -- takes at least a week to develop fully after a pipe cleaning with Blue Away. One very small section on inside of bend gets a tiny bit bluish, rest turns gold. Mild gold section also develops in exhaust pipe just short of bevel zone at end of pipe. Oil is Mobil 1 Clean 5000 10W40. Valves are due for adjustment soon.

Pipe cleaned with Blue Away to dull chrome neutral color. Air screw reset to 2 turns out. Idle readjusted.

Air screw setting experiment starts now.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/09/06 at 20:44:11

Results for 2.0 turns out were a very slight improvement in performance. There is a mild improvement noted in around town pick up. Open road willingness to rev freely to 70+ mph is noted with the "out of breath point" seeming to be a few mph higher than previously seen.

Bike spits occasionally where it used to do a mild backfire (backfires are reduced numerically to a slight degree). Pipe is neutral with very slight gold hints with the same blue patch coming back underneath the pipe as just as it exits from the engine. Pipe is less gold tinted than it was before.

Gas mileage for this week is 48.2 MPG which is in the middle of the span noted over the six months I have been riding the bike. This is not a significant change.

Pipe cleaned with Blue Away to dull neutral color again. Air screw turned in a quarter turn to 1 3/4 out from full bottom position. Idle speed required a slight increase for this quarter turn adjustment.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/14/06 at 17:21:51

No improvement in performance noted for 1 3/4 out setting. Pipe is neutral with slight purple/gold hints with blue patch on bottom of pipe right beside head exit and similar sized blue patch on outside of curve (in line with the patch on the bottom inside edge). Must be some sort of gas flow thing going on inside the pipe to provide the localized blue zones, but their presence says I am getting back towards the lean side again.

Gas mileage is worse at 44.84 MPG. There is no improvement in top end and accelleration seems to be no better (perhaps worse). If anything more off-idle throttle twist is needed to get the same reaction as I am used to seeing.

Bike is spitting and backfiring about like "normal", so a slight decline in backfire action for this setting compared to 2.0 turns out.

I'm going to continue one more quarter turn just to verify I have really crossed my optimum point and indeed am going the wrong way now.

Pipe cleaned with Blue Away to dull neutral color, air screw turned to 1 1/2 turns out. Idle speed had to be increased again after this change.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by Brewbrother on 09/14/06 at 17:45:43

do you adjust your idle screw so the bike is close to dying before you adjust the air fuel screw??

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/15/06 at 03:38:14

No, in this experiment I am trying to see what the running characteristics are for each setting, so I just provide a correct idle speed after the adjustment is made.

Tuning the air screw to provide the best idle speed (or judging the central span of best idle speeds by splitting the difference between the in and out choke points) yeilded a slightly rich condition on my bike when I first did it according to general list recommendations.

Now I am doing it emperically by slow stages, seeing the mileage and operating characteristics for each stage and NOT considering the effects on idle speed. If I find good operating characteristics, I will give it the idle required to live there.

I think we put on blinders when we just go for a maximum or "most central" idle speed -- when what we really want is best accelleration off idle up through mid range, the best gas mileage and "most neutral" pipe color.

Idle speed is just another very easily made adjustment that can be made AFTER we get the things that are really important to us.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by serowbot on 09/15/06 at 07:29:45

There are many myths about the black art of carb jetting. Gold pipe is lean, blue pipe is rich, is a myth. The pipe discolors from heat, first to gold then to blue, then to blue black. Can be from running rich or lean.
A big single with a thin pipe will discolor faster than most.
Also be aware that ambient air temp and humidity will affect your overall jetting and performance much more than turning the idle mix screw. If you notice better running in hotter, more humid days, your rich, better running in cooler, dry days, your lean. Your looking for a middle point in jetting that suits an average of weather conditions in your area.
Backfires (afterfires) can be caused by a rich or lean condition too. Best to try to notice if the condition increases or decreases in humid weather. More backfires in high humidity is a rich backfire.
Also you want to adjust the idle circuit for smooth idle, pilot jet size for mileage, needle and slide for acceleration, and main jet for WFO or top speed.

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/15/06 at 14:16:23

Pipe colors -- heck we can't even keep the same interpretation going on what causes which color.

Historically, I have always heard gold was rich and blue/purple was lean with gold being "rich/cold" and blue/purple being "lean/hot". You heard it the other way around.

Go figure.

Now here's another myth buster for you -- I can't find that magical neutral chrome color existing in between the gold and blue ranges -- what I do find is sections of each showing up on the same exhaust pipe !!

I got myths falling all over themselves over here ....

What I can suggest is using maximum or "middle" idle speed alone to make decisions isn't refecting all the post mod variables on a stock bike very well. Max idle speed was too rich on my bike. Middle would have been closer, but still a bit rich really.

Better running characteristics existed BELOW the point of maximum idle speed on my Savage (and perhaps on yours as well).

First, write down what you consider important to you. I value good accelleration, best gas mileage, no severe spitting & backfire action and a good pipe color in that order. Then test for it, writing down your results as you go.

You will get closer using this method than trusting an idle speed to magically tell you the whole story.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by Brewbrother on 09/15/06 at 18:35:41

Oldfeller2 wrote:

I adjust the idle screw down before tweaking the air
fuel screw so I can more easily hear the sweet spot. Too many grateful dead and rolling stones concerts in the 70's make it a must.

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/23/06 at 11:36:54

As anticipated, leaner didn't work better -- it ran worse.

Going back to the best zone (which was 2 turns out) I started turning it in by the 1/8 turn. Currently best acceleration and best spitting and most OK gas mileage exists at 1 7/8 turn out (44.28 MPG) and the pipe is running two very small blue patches and the rest of it is turning very slightly gold.

I think this is about as good as it gets (and honestly I'm tired of messing with it).

I have no proof that this air screw setting actually changes due to the season as has been mentioned by some, but I will be watching out for that sort of thing over this upcoming fall/winter changeover.

Oldfeller

Title: Re: Turn in or out to "lean" some?
Post by georgekathe on 09/23/06 at 13:52:24

interesting about pipe color changes & whether do/don't reflect carb tuning. I thought it did, but certainly correct about thin piping leading to blueing.

BMWs have always "blued" - supposed to be part of their "charm," & both I've had access to seemed to run fine so??? think with a bike costing $15-16 K they could have "dialed" this idiosyncrasy out, wouldn't you?

george :)

Title: Re: Turn in or out to "lean" some?
Post by Oldfeller2 on 09/23/06 at 17:16:45

Isn't the BMW pipe a small diameter single-walled pipe? Maybe Germans consider pipe coloration to be a necessary indicator of motor tuning and wanted it to be something that must be clearly visible to the rider? A cultural German techo-mildset attribute, in other words.

I never noticed the old Honda 550 Guzzi style bike bluing its pipes although it too took a pretty sharp bend right out of the head. Once again, the Japanese generally don't like blue pipes and go for double wall construction.

I have had several Hondas and a Yamaha that didn't blue at all, nor did they turn gold either. Construction on both was double wall pipe and the diameter of the pipes were considerably smaller since they were twin cylinder bikes.

Is the pipe on the Savage a double wall construction? If so my isolated zones of blue may be inner and outer wall touch points where heat is being directly transferred between the layers of the pipes. If not, then the location indicates flow points where hot gas flows directly against the pipe walls (this is how I interpret the blue spots since they make sense that way).

I dunno .... who has cut a Savage header pipe to shorten it and knows the construction details?

Oldfeller