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  #31  
Old 04-29-2009, 02:24 PM
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I now have a CV40, which I have molested, and a service manul, next to my recliner, in my living room. I think that makes me the subject expert.
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  #32  
Old 04-29-2009, 02:24 PM
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I have the '02 manual and couldn't find any reference to that screw, much less the adjustment.

I was going to wait 'till I got home to post this, and I'll make a more complete argument when I do. But I'll give you something to chew on. I think I'm going to leave the stock can installed and replace the stock element with a high flow K&N element. The reason is, and I believe it, HD engineered the stock can to produce torque in the idle to 4000 rpm range. My bikes rarely see 4 grand, if ever. I couldn't care less what happens over that cause I NEVER run it that high.

I'm the short shift king. Tach usually swings between 2 and 3, 3500 if I'm feeling frisky. I like what my bike does now, I just want more of it.
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Old 04-29-2009, 02:32 PM
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I doubt, the manual reference the screw, since it covered. As for air filter, I have no idea on the housing. But changing element is good.

The HD one I bought in 07 fell apart in months. The K&N HD used to sell, that I bought in 04, is still good.
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Old 04-29-2009, 03:05 PM
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  #35  
Old 04-29-2009, 03:10 PM
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dan, I think I have all these parts still:

http://www.harley-performance.com/stage-1-carb-kit.html

I can check at home if you want me too.....I needed the ez mixture screw and those parts but I bought 1 for the dyna and 1 for the rk, long story, I never used 1 set.....I can give you a good deal on it.
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Old 04-29-2009, 04:37 PM
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Dan, I haven't read Minton's article so I don't know what he tells you about idle tuning. I'll run through what's worked for me over the last 30 years of dirt and street bike tuning.

Pilot jet idle-1/8 throttle
Needle- 1/8-3/4 throttle
main jet- 5/8-full throttle

This gives you an idea of where your need to adjust.

Pops through carb when accelerating-lean
Pops through exhaust on deceleration-lean
Plug reading only works if you use a fresh plug, start the bike up and make a full throttle run then shut down and coast to a stop without idling.

Idle screw/pilot jet adjustment

Warm up the bike thoroughly.
Set idle speed as desired
Start with idle mixture screw 2 turns out.
Open the screw slowly until you detect a change in the sound of the engine. Your enriching the mixture so the engine will start to sound somewhat blubbery(don't know what other word to use, but the engine will not sound crisp).
Shut off the engine and screw in the idle screw counting the number of turns until SEATED, do not overtighten, just seat the screw.
Open the screw back to your starting point.
Restart the engine and turn the screw IN until the engine starts to slow or stumble SLIGHTLY.
Shut off engine and screw in the idle screw counting turns again.
Split the difference between the low and high setting and this should be within a quarter turn of perfect.
This will change with weather and altitude.
Colder weather will probably require opening the screw up 1/8-1/4 turn and closing the same amount for hotter than normal weather.
Higher altitude will require closing the screw about 1/4 turn for every 2500 feet above the baseline altitude you tuned at.

If you look in the Dennis Kirk catalog they list a long mixture screw with a knurled knob for your carb. Makes adjusting mixture much easier to do.

Write down your setting once you get it where your happy. This way if you change for altitude and weather you can always reset if it seems you got to far away from your baseline.

Needle adjustment is much more subjective, you just have to ride the bike and see how it responds.
If you get poor mileage after tuning it's most likely the needle. One clip position can make a 5-7mpg difference in fuel economy.
Generally if the bike seems to be running hotter than expected your probably lean.(lower the clip on the needle one position which raises the needle up and richens the mixture quicker as you open the throttle)
If the engine seems boggy/blubbery on acceleration your probably rich.(raise the clip one position on the needle)
Carb farts when opening the throttle can be either slightly lean on the needle or idle mixture or a slow to open accelerator pump or rider error.
You almost can't avoid carb farting if you tend to try to release the clutch which loads the engine BEFORE you start to raise the rpm. The CV carb design uses engine vacuum AND intake velocity to control mixture so loading the engine early without raising rpm causes a high vacuum/low air velocity, so the slide slams open but the intake velocity is insufficient to pick up enough fuel and the mixture goes lean causing the stumble and carb fart.

Your main jet is the least important change as far as everyday ridability. You will rarely use the main jet. Probably 5% or less of the time you are using the main jet.
The only real way to tell if you need to change the main jet is to check the plugs and make some acceleration runs to see if the bike pulls hard through out the entire range of throttle opening or if it feels like it loses acceleration as you get into the main jet.

Using this method on the wife's XL1200 I've gotten her bike 54mpg highway really good acceleration and no carb farts or decel popping.
I'd expect a big twin to produce at least 45 mpg highway.

Joe
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  #37  
Old 04-29-2009, 05:15 PM
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Quote:
Originally Posted by jasilva View Post
Pops through exhaust on deceleration-lean
Joe
When tuning my 98", I over jetted. When lefting off the gas, the bike was erieily silent. I like the popping, bah-bah-bah. But I am weird.
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  #38  
Old 04-29-2009, 05:33 PM
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Quote:
Originally Posted by BigSwede View Post
Dan, I tuned my Fatboy the same way you are looking to tune your bike. I did a stage 1 (filter and pipes) and used the Sportster needle/air mixture screw adjustments to get fairly close to what they needed to be. Took some time to get it to where I liked it, but it worked. This came among all the discussions that I needed a thunderjet kit to rejet everything and get a dyno tune. While I may not have gotten spot on, it was close enough and the bike ran well enough for me to be happy with it.
What Frank said. I used the 88 Sportster needle and a little tweak on the idle mixture on my softail. I had a Ness BS and a Fat Cat on it and it ran great.
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  #39  
Old 04-29-2009, 08:13 PM
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Minton on carb jetting:

http://www.americanrider.com/output.cfm?id=1021951

Quote:
After following the local Harley Davidson dealer's recommendations, installing a Dynojet kit, and speaking with the Dynojet's reps in Las Vegas, I am still only getting 36 mpg on my new TC88B Softail. It originally got 47 mpg for the first 3,000 miles before I decided to rejet the carb.

I installed the new spring, drilled the hole in the slide with the #29 drill, installed E clip on the fourth groove, and installed a needle. I also installed the emulsion tube and DJ 180 main jet. I initially installed the #48 slow jet as per Harley, but have since put the #45 original slow jet back. I did not install the accelerator pump nozzle weight or ball as the Harley shop and Dyna Jet people told me not to.

would like to get back in the mid-40-mpg if possible. Any suggestions would be appreciated.

Mark Carty



A

I get a steady flow of questions regarding carb jetting and the Dyno Jet kits, and I'd like to answer them once and for all. Before addressing this, I need to set the stage about fuel mileage. The mileage one records is dependent upon a number of factors. The speed you travel is one. Mileage plunges dramatically above 60 mph or so; a bike that gets, say, 45 mpg at 60 might only record 30 at 80 mph. Another important influence is the size of the hole you and your bike poke in the air. An FLHT touring rig needs about 12.8 horsepower to go 60 mph while a Sportster gets along with about 10. Headwinds, climbing and elevation all affect fuel mileage. Total gross weight has little influence at steady speeds; however, carburetor jetting has dramatic effects on fuel mileage.

When I talk with someone about fuel mileage, I find it useful to set a test standard. Here is my standard: a steady 65 mph on a flat, windless road. These are conditions most of us can find and safely use. Using this standard, stock Harleys typically deliver 45 to 55 mpg. The lower for the big touring rigs and the higher for the Sportsters. I have found that properly jetted Evo, Sportster and Twin Cam Harleys deliver mileage between 42 and 51 mpg, using the test standard defined above.

Keep in mind that stock engines are tuned very much on the lean side of correct jetting. When we modify our carburetors - to get rid of the "lean staggers" during warm-up and to smooth out throttle response during acceleration within the lower throttle settings - we can expect somewhat lower fuel mileage at cruising speeds. However, that loss need only be a couple of mpg, not ten.

Your 36 mpg is about right for a Dyno Jet-kitted Harley. From your mileage I presume that you have either a Dyna or Softail series motorcycle. The big touring machines usually get closer to 32 with the Dyno Jet kit. I have talked with many (more than a hundred) owners who have installed the DynoJet kit and who have been disappointed with the results.

An FXD or FLST that delivers 36 mpg at 65 mph is running too rich. That too-rich condition has consequences. Range is an obvious possible problem. Many riders aren't too concerned about range as they like to stop more often than the bike needs a re-fill anyway. Climbing ability is a more important concern for those of us who need to go up or over mountains. A 36 mpg bike will probably start misfiring due to its over-rich condition by 4,000 feet, maybe even 3,000. By contrast a stock or correctly jetting engine should get to at least 6,000 feet before getting grossly rich, 7,000 feet is better and achievable.

Another factor that affects mixture is the needle and needle jet (emulsion tube) of the Dyno Jet kit: they're made of brass, so they wear rapidly against one another. Your rich mixtures will get even richer with time, perhaps after only 10,000 miles of use.

The stock needle and needle jet are made of hard anodized aluminum and hard brass respectively. There is virtually no wear between these components. The Japanese carburetor industry long ago stopped using the brass-on-brass combination. For example, the original ***** 750 had brass needles and needle jets, and mileage would drop from about 49 to 39 mpg in 10,000 miles due to the wear between these parts.

I do not enjoy saying these things about a company's product, especially when I have reason to believe that the company is doing its best, and especially when some of the employees are friends, at least professionally. However, I cannot ignore the welfare of our readers. You are, ultimately, why I write about what I know.

If you would like a better jetting solution to the stock jetting problem, read my answer to the next question.





Q

I have ordered a new 2003 FLSTF Fat Boy. I intend to add a Screamin' Eagle air cleaner and Cycle Shack slip-on mufflers. I know the carburetor is going to be lean. What should I do to fix it? I'd like to stay with the stock carb and probably won't modify the motor any, at least for some time. I've been told and have heard lots of things. About half of what I've been told contradicts the other half! I trust you judgment and I'd like to know what you would do?

James Morris



A

You are making good choices. The Screamin' Eagle air cleaner is a fine product that passes all the air a stock-port engine can use. The Cycle Shack slip-on mufflers are well made and produce good power over a wide rpm range. Most brands of small slip-on mufflers work about the same despite what the advertisements may claim.

Stock Harley jetting is very lean from just off idle to about 1/4-throttle. This is also true of all road-going bikes sold in America for the last quarter century. However - and this is important - at idle and above 1/4 throttle the jetting is pretty good.

Harley's Keihin CV (constant velocity) carburetor is based on the basic Amal slide carb design from the early post-World War One era. And therefore, it shares similar parts which perform similar functions:

Idle and just off-idle air/fuel mixtures are controlled by the idle jet which is fine-tuned with a screw. Both the jet size and screw setting are important.

Off-idle to approximately 1/4-throttle mixtures are controlled by the straight-diameter part of the needle together with the inside diameter of the needle jet, in which the needle rides. This is the range that is overly lean for best engine performance on stock motorcycles. Either the diameter of the straight part of the needle or the inside diameter of the needle jet must be changed to affect mixtures in this most-used throttle range. Nearly all riding is done within this off-idle to 1/4-throttle range.

From about 1/4 to 3/4 throttle, the taper of the needle is the main mixture control. One normally raises or lowers the needle to fine-tune mixtures within this range.

The main jet takes over at about 3/4 throttle and is virtually unimportant below that opening.

If you would like to learn more about how to diagnose these carb sub-systems, I invite you to download the Mikuni HSR Tuning Manual (www.mikuni.com, click on the picture of the carb, click on the hot link "Manuals"). I wrote this manual for Mikuni, and although it directly addresses to the Mikuni carb the diagnostic principles apply to the Keihin CV and many other carburetors as well.

All you really need to do to get your stock carb right is:

*Buy and install a stock jet needle for a 1988 or '89 1200 Sportster. This needle was developed for the early Sportster Keihin CV carb that was not equipped with an accelerator pump. As such, it is richer in the off-idle to 1/4-throttle range and works just right.

* Remove the soft aluminum plug covering the idle mixture screw. Back the screw out to slightly richen the idle mixture (1/2 to 1-1/2 turns will do it).

*

DO NOT

* Do not change the main jet; the stock one is just right with a free-flowing air cleaner and mufflers. Yep, the stock main jet is rich. If you find this hard to believe, use the main jet test in the Mikuni manual to see for yourself. You see, the main jet size is not controlled by emission testing and the government is not very interested in mixtures at full throttle. The factories are free to use any main jet they want and, for some reason, all the stock bikes I have tuned over the past 25 odd years have had somewhat rich main jets, including Evo & Twin Cam Harleys.

* Do not change the slow jet; the stock one is just right with an open air cleaner and free-flowing mufflers.

* Do not install straight, open pipes, especially long ones. If you do, forget everything I've said. Straight open exhaust-equipped engines run poorly in the 2,000 - 3,500 rpm range and no amount of carb tuning can fix that.

Another article from Minton:

http://www.americanrider.com/output.cfm?id=1815121

Quote:
We continue to get letters and emails with questions about tuning the stock Harley CV carburetor. I have written about this before, but reader interest warrants a revisit.

The Keihin constant-velocity carburetor was stock on Harleys for more than two decades. It has, for EPA reasons, always been too lean in the lower one-third of the throttle range.

The solution is simple, normally requiring only one new part and one re-adjustment. A couple of simple changes can make the stock carburetor sing like a bird, and I mean a canary, not a crow. You do not need, nor do I recommend, any non-Harley parts.

First: The idle-air mixture screw

The factory’s idle-air mixture screw setting is too lean for best performance and it should be adjusted. This is true for all stock as well as altered engines. Here’s how to do it:

1. Remove the soft aluminum plug at the bottom of the carburetor that covers the air mixture screw. You will need to remove the carburetor to do this.

2. Turn the air screw all the way in until it lightly—and only lightly—bottoms. Turn the screw out one turn as a starting position.

3. After re-installing the carb, and with the engine warm and idling, use a small screwdriver to turn the screw slowly out until the engine begins to run unevenly.

4. Now turn the screw inward counting the turns, until the engine runs unevenly.

5. Finally, back the screw out halfway between these two “uneven” points. It’s likely to end up between one and two turns out from the original stock position.

Second: The jet needle

The most important change, and the only item normally needing replacement, is the jet needle. Use one from an early Evo Sportster (H-D part no. 27094-88). It has a very slightly smaller diameter (0.0004”) in the straight section above the beginning of the taper.

The new needle slightly richens the part-throttle mixture and is responsible for nearly all the improved running qualities this procedure provides. Mileage may lessen by one or two mpg in a stock engine. Modified engines often improve by a like amount.

Also, the stock slow-speed (idle) jet that is accessed from the float-bowl chamber should be correct and rarely needs replacing. Poor idling is almost always a consequence of the factory’s lean mixture- screw adjustment. Do not consider replacing the jet until after you have re-adjusted the mixture screw, changed the jet needle, and thoroughly tested those alterations on the road.

If the engine continues to run lean at or just off idle (hesitates or “pops” into the air cleaner), you might need to replace the stock slow jet with the next larger one.

Street bikes seldom run on the main-jet circuit. The main jet has no function or effect below 3/4-throttle and then only in the upper half of the rpm range. Since the stock main jet is overly rich to begin with (by one or two sizes) it is seldom necessary to change it. Really—hardly ever.
One last one by Minton:
http://www.americanrider.com/output.cfm?id=1674757

Quote:
QI have a carbureted 2001 FLHR with 100,000 miles on it. Stage One, a K & N air filter, and Bartels mufflers were added at 5,000 miles. Other than this, it is stock. It has always started and run without a hitch. However, I have never thought the carburetor was tuned correctly for mileage and acceleration. After reading your articles I am sure of it. I live in Houston. Could you please direct me to anyone you think would be qualified to tune my carburetor as described in your excellent article? I do some of my own maintenance work, but would not feel qualified to do the carburetor tuning.

AJay, I sincerely wish that I could confidently give you the name of a single person in Houston or Texas or any other place in America who can properly tune your Harley-Davidson carburetor. I cannot. I am sure that they are out there but I have no names or locations to offer you. By implication, I am saying that skillful carburetor tuners are rare.

Useful and accurate information is the problem, not intelligence, not curiosity, nor dedication. Harley-Davidson simply does not provide tuning information for their carburetors because they dare not; you know why this is so. A natural result is poorly tuned carburetors.

Given that Harley mechanics frequently work with altered engines, they must also deal with carburetors that are even further out of tune than when stock. Few have the equipment to learn what would be best taught by Harley-Davidson. So they get by with personal experience and rules of thumb. Some of those rules are wrong—open mufflers and high-flow air cleaners do not necessarily require larger slow and main jets. Raising the needle does not richen air/fuel mixtures at cruising speeds.

The result of fitting a larger slow jet and main jet is ratty running at low speeds and less power at full throttle. The engine continues to run lean at cruising speeds and throttle settings. Many of you surely recognize this description as applying to your “tuned” carburetor.

Testing and on-the-road experience show that the stock slow jet is the right one for virtually any combination of air-cleaner and exhaust modifications. The main jet is too rich when stock and becomes correct with most open mufflers and air cleaners. It is the jet needle that needs to be changed (to one from an early 1988 Sportster).

A majority of Harley Keihin carburetors need only an idle mixture-screw adjustment (1 to 1.5 turns out) and an early Sportster needle. These changes are simple and very effective. The main jet is okay. The slow jet is okay. We have published this specific information several times over the years and I wish Harley could do the same.

As I said earlier, I like his philosophy and think he's right. I sum it all up by saying, a stock carb is close to right and only needs minor adjustments to eliminate the lean condition. As it stands, my Dyna runs pretty good and I do not want to turn my bike into a fuel guzzler by over jetting. Minton says this carb setup will run almost any air cleaner/exhaust combination.

My thought here is try it his way. What have I to lose? If it needs more, I can do more. It seems to have worked for BigSwede and TalonChief. 'Zerk says he over jetted using a jetting kit just as Minton says will happen.

While I liked the article 'Zerk referenced, I'm of the opinion it's over kill. I'd like to try the Minton set up with a set of Andrews 21 cams as well. But we'll discuss Minton's version of a torque motor after we hash out the jetting.

What say you, Joe...anybody else? I'd like some real debate on this if we have dissenting opinions.

Thanks all.

Dan
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Old 04-29-2009, 09:44 PM
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Quote:
Originally Posted by Dirty Dan View Post
'Zerk says he over jetted using a jetting kit just as Minton says will happen.
I don't think I over jetted. I think I over spent buying the Dixon kit. $100 for jets for various set ups I didn't need. Changed out emoultion tube, which I think was over kill.

The article by Minton, loses me when he says to start at 1 turn out, when mine came from factory already at 1 3/4. Unless I misread it.


You can change jets on the bike, so not a big deal.

I suspect, you won't see the difference, other then dyno. I know I am not that sensitive.
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Old 04-29-2009, 10:10 PM
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Sorry, my bust.

Here he says "Remove the soft aluminum plug covering the idle mixture screw. Back the screw out to slightly richen the idle mixture (1/2 to 1-1/2 turns will do it)" which I take to mean an additional 1/2 to 1-1/2 from the stock setting.
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Old 04-29-2009, 10:12 PM
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Originally Posted by y2kflhr View Post
dan, I think I have all these parts still:

http://www.harley-performance.com/stage-1-carb-kit.html

I can check at home if you want me too.....I needed the ez mixture screw and those parts but I bought 1 for the dyna and 1 for the rk, long story, I never used 1 set.....I can give you a good deal on it.
Lemme see what happens with the jet needle and idle adj. Do you have that long idle air adjustment screw with the knurled knob that can be adjusted by hand?
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Old 04-29-2009, 10:27 PM
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Originally Posted by Dirty Dan View Post
Sorry, my bust.

Here he says "Remove the soft aluminum plug covering the idle mixture screw. Back the screw out to slightly richen the idle mixture (1/2 to 1-1/2 turns will do it)" which I take to mean an additional 1/2 to 1-1/2 from the stock setting.
I probably can't read. He probably meant additonal and I read as from start.

I got plenty of time to reply to emails, but can't seem to find enought time to sit and read
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Old 04-29-2009, 11:16 PM
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Dan, I think I pretty much agree with and said the same thing as Minton. ONLY change the pilot jet if your final adjustment will be MORE than 2.5 turns(go larger) out OR less than 1.5 turns(go smaller). If your still running an 88" then the main is probably fine. Be careful with the needle clip position as I said before this can really make or break your fuel mileage. Wife's sporty went from 43-45mpg up to 50-53mpg by raising the clip one postion(drops the needle and leans the mix). If you go back and read the second article of Minton's that you quoted, specifically the last couple paragraphs he sums up pretty much the same as I did.

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Old 04-30-2009, 01:45 PM
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Originally Posted by jasilva View Post
Dan, I think I pretty much agree with and said the same thing as Minton. ONLY change the pilot jet if your final adjustment will be MORE than 2.5 turns(go larger) out OR less than 1.5 turns(go smaller). If your still running an 88" then the main is probably fine. Be careful with the needle clip position as I said before this can really make or break your fuel mileage. Wife's sporty went from 43-45mpg up to 50-53mpg by raising the clip one postion(drops the needle and leans the mix). If you go back and read the second article of Minton's that you quoted, specifically the last couple paragraphs he sums up pretty much the same as I did.

Joe

Yea, I thought it was about the same. It's still 88". For the time being it will remain that way.
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