Fine-tuning your Harley Davidson with mixture screw
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- Опубликовано: 14 май 2022
- This video is to show you how to fine-tune your Harley Davidson after giving your carb a good clean and possibly changed some bits like needle, slow jet etc.
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It's great that you not only show how to achieve the proper tuning, but also how to check with idle recovery and startup, thanks so much.
Most welcome
Articulate and concise. I rebuilt a carb and there was sneezing, needed to back the screw out another 1/2 turn to achieve the correct throttle response from quick twists of the throttle. Thank you
I’m glad it was helpful.
Your videos are filled with good information and helped me a lot understand how to work on my CV carb, which was a first for me. Thanks a lot !!!!
I’m glad you are finding them helpful!
Great video, I appreciate you explaining the air mixture part. Most people just want to adjust the idle.
Great presentation of a difficult procedure. Thanks for the help....
Welcome Richard. Thanks for the comment.
Great overall video. When you go big bore kit or cams, or both, you will have a hard time with this if you don't re-jet your low end jet. Depending on where you are, elevation, it can vary a lot. You just have to play with the jets and see which one works best for your bike following Aron's procedure. For example, my bike has the 95 big bore with 211 cams, I am having to go to at least a 48 jet, up from a 42 which was stock. Also been told at sea level where I'm at, I may have to go to a 50 or 52 pilot jet then adjust my mixture screw. The old guys are telling me if you are more than 1 1/2 to 2 before it smooths out, you need to re-jet the pilot jet. I am currently doing all of this trying to find my best jet for the HP and mileage. Doc Harley at Low Country HD told me to start with a 45 and 2 1/2 turns on the mixture screw. I think it depends on the bike but I believe if you are more than 3 turns out on the mixture, you need to go to a bigger jet to get the best performance. Just my 2 cents.
Thank you. I can imagine with a different set of cams and big bore kit, it would require bigger slow. Mine is stock and initially, I also followed that “rule” you mentioned and ran it with a 48, but however hard I tried to set it right it would always run too rich and very sluggish when fully warmed up. It’s worth experimenting with it though, maybe some people have different air cleaners and exhaust, stock needle, even (elevation as you mentioned)and will work. Mine definitely runs at its absolute top performance and gas milage with this set up (with the 88 Sportster needle). (here in the UK :)
Thanks man, watched a few videos of this and yours is very informative.
Thanks Martin.
I'm from Russia and it's the creat video for HD carb fine tuning.
Thanks a lot. I’m glad it’s helpful.
A lot of good key tips on characteristics of lean and rich thank you!!!
GREAT JOB EXPLAINING. MUCH HELP.
Best cv40 tuning video out there
Appreciate that
If you install the extended mixture screw from CV Products, which has a larger screw head, you will be able to turn it in or out with your fingers, and without the use of a screw driver. It makes it much easier to do.
I have tried it before, but I couldn’t do it as precisely. I kept covering the markings on the head of the screw with my thumb and finger, losing track of turns. It might work for some people but didn’t work for me.
@@aronsgarage834 One other question. And I am just guessing here, but does it really matter if you count the number of turns you turn the mixture screw in or out? Since you are looking for the motor to stumble when you turn the screw in, it should be close to bottoming out anyway, so no need to count the turns in. When turning the mixture screw out, you are looking to get the highest rpm and engine smoothness, and so it does not matter the number of turns you turn the screw out. The sweet spot we all talk about should come when the engine runs the best, and does not depend on the number of turns...what say you?
In that sense, it doesn’t really matter. It just helps you figure out where you should be, compared to your “baseline”. But either way you do it you should be fine. It’s still advisable to count the turns once you have found the sweet spot to record it, and to make sure it’s not too far out…( as that would indicate needing a larger jet)
That extended screw will also not be the exact same taper/length as the stock. That and the extra mass with the types of vibrations it's subject too.... idk if that's going to end well.
I would appreciate an extended or easy access idle speed screw though. Been thinking of trying one off my klr, my Yamaha atv or other units and seeing if it would work. They run it so dang close to the throttle cables.
My new to me 2000fxdwg has the 44mm 'race' cv carb... bored 95" with a tw6h cam set, ported heads and sitting about 10.2:1 compression (185 cranking compression). I'll never get a smooth idle out of it. Runs strong, but slight surge low load during the transition between idle and cruise. Have a 50 piolet jet in it, 52 just makes it to rich at idle and doesn't help much low speed in town.... just how it is I guess. A few shims under the needle didn't help much either.
Great presentation! Please Mikuni HSR 42 video
Hey man, first just want to thank you for the informative video. I have a 2002 Dyna Lowrider with a K&N filter and 2-1 pipe (Thunderheader).. Jets are 190/48.. wasn’t able to check float level and bike was running great before, so I didn’t mess with it. First time doing anything with a carb and tried tuning as demonstrated, though I’m finding it hard to gauge. I’m at roughly 3 turns out.. was at like 3.25 turns but was having some decel pop, so turned it back in to 3, which seemed to help. One thing I noticed is that even after bike was at operating temp, I fired it back up after fueling up, and it would idle, then rpm would dive. I increased idle at approximately 900 rpm and seems to be idling at about 1000 when out riding. The bike doesn’t seem to pull nearly as hard and the exhaust note is quieter/doesn’t have the depth/bass it did. Haven’t changed spark plugs yet so I can’t comment on those. I’m 490 ft. Above sea level and temp is 80 degrees Fahrenheit. Any thoughts are appreciated. Thank you
Hey bud, Sounds like it’s a bit too rich. What color are your plugs?
So did you take the carb apart and clean it (if so, did you replace anything) or just performed the fine tuning while bike is idling?
Really liked all your video's. Followed your advise to the letter. Stock motor and exhaust. On the first start up ran and rode great with a 1/4 turn in on the air mixture screw . I'd like to thank you for sharing your knowledge and time in carb tuning. So with that when will you be posting more content.
I appreciate your positive feedback. Will be posting soon again, especially in the spring when I’m planning to film my hydraulic tensioner conversion. Just moved house and have a newborn, so currently running pretty busy 😃
I've been riding exclusively Evo powered HD bikes (with a CV40) most of my life. One thing 99.99% of these motors do is idle at 850-900 rpm's when semi warmed up and then bump themselves up to 1,000 rpm's once they are up to full operating temperature. This is acceptable to me as they benefit from having oil pressure but it might be frustrating to most people. If you wanted the 850-900 idle you will need to carry your screwdriver with you and adjust the idle screw once you have the mill fully up to operating temperature. Even better if you are able to hit the highway for a bit. Just my thoughts after several years of tinkering. Great video 👍🏻
That’s absolutely correct! Mine goes up to 1,000 fully warmed up as well. I don’t mind it, either. I installed a quick adjust idle screw, but I wouldn’t mess around with it every time I ride. These CV40 carbs work and perform really well when tuned correctly.
@@aronsgarage834 I've also got a "hotrod" 1994 Fatboy that I installed an Ultima 113 El Bruto in. I am currently running a CV44 carburetor on it with a factory airbox that is highly modified. I removed the Ultima rocker arms and covers and am running Evo ones to make it appear stock. It's the perfect sleeper. I recently Dyno'd it and it did 125hp/125tq (165mph) it's soo sick!
Sounds like a beast! 😎
@aronsgarage834 Its a white knuckle ride!
My twin cam is running rich ( plugs are black ) Do.i need it re jetting ,or can i simply adjust the mixture screw.?
I have a device called a colourtune ( never used it ) it goes in the spark plug hole and on tickover you turn mixture screw till you get a blue flame in the view glass .
Have you any experience with this device ,?
I'm rebuilding my carb right now and put 190/48 jets and the Sportster needle. I have an 01 FXDX 88" with Big sucker intake and 2-1 pipe. The tuning sheet said to put the 48 in so I did and put the carb 2 turns out. Havent put it all back together as some parts got stuck in shipping. I WAS running a 46 jet but would have random spits and coughs at about 3 turns out with the new intake. Hopefully the 48 will be good at 2 turns on the mixture screw. Im worried its too fat but if it is, I have all the other jets (45,46,50) so i can swap whatever I need to. The bike ran fantastic on the 46 with a smaller intake, but it would barely run with the new one. Just coughed anytime I gave it throttle or barely had power even at 3.5 turns on the mixture screw. Lets hope I'm on the right track!
Sounds good! Let me know how it turns out.
@@aronsgarage834 It runs amazing! Thing eats tire when you rip full throttle. Honestly it has never felt so powerful. Just got back from riding and still can't believe it. Choke for 30 seconds and she was ready. No coughs, sputters or hesitations. 2 turns out on mixture screw with that 48 jet did the trick!
Right on! Glad it worked out!
My Evo is fouling plugs. I'll perform the procedure you've kindly shared and hopefully it'll sort things out. Thanks.
Hopefully. Let me know how it turns out.
Fully cleaned and rebuilt my 99 FXD. 190 main jet, 45 slow jet. I'm 3.5 turns out on my mixture screw (started at 3 but was getting coughing and hesitation) and the bike feels great throughout the whole rev range. Super smooth and no sneezing or coughing at all.
My question is, on a cold start (70F ambient) with the enrichener knob fully out the bike will start up at 1200rpm for about 3-5 seconds and immediately drop to 1000rpm. At 7:00 you indicate that it's probably rich which doesn't make sense to me. Shouldn't it be the other way around? If I follow your statement and lean the bike out I will get coughing and bogging again
If it is idling too low with the enrichener knob fully out wouldn't that indicate that it needs even more fuel to raise the revs? Not less?
If it’s lean it would have higher rev on choke as there is more oxygen.
Based on your settings ( mine is pretty much the same) you should have around 1500 rpm choke fully out and dropped to 1200-1300 after like 10 seconds. Maybe your choke assembly needs looked at?
What color are your plugs?
Hay man thanks this is great, can you write here how to know if it’s rich or lean. ? What you are saying at the end of the video? I think that’s super important
Yes, sure. If lean you’ll have a lot of popping on decel, and if you blip the throttle it won’t drop properly (hangs a bit). Also, after a cold start it will take ages to get it to idle without stalling, rough idling, spark plugs will be very light greyish.
If rich, performance will drop once properly warmed up (it’ll be sluggish), black plugs, may smell unburned fuel when idling,
Awesome broouuu what about deccel poppin?? Any advice. I’m too rich now so I need a little adjustment. Stock carb 05 fxdl. Even original screw cap cover.
Are you sure stock carb still has the stock jets? Did you check? 45 slow 190 main.
How many turns out is your mixture screw? Spark plugs black?
I’ve used this channel to work on a project 97 fxdl appreciate the info. I recently took apart my carb and cleaned it how do I know where the starting point is for the mixture screw? Hand screw it all the way in?
Yes, screw it all the way in until it seats (gently) don’t over tighten. That is your starting point.
Thank you
What causes one to backfire thru the carburetor while its idling and warm
Normally a weak mixture, maybe a leak around the manifold or jetting issues. Though it can also do that when it’s too rich. I had that issue when I had a 48 pilot in instead of the 45.
If yours only doing it when warmed up, then it’s likely to be rich. Have you checked the color of your plugs?
Hey man if my road glide is running rich would that explain the throttle bog in turns and normal riding and some exhaust sounds (pop and air pulling) and would that cause the idle to sit at 8-900 at temp?
The popping could indicate lean especially when you give it some throttle and on deceleration. If you’re rich you’ll notice when the bike is bit cold still, it will pull pretty strong, but when it gets to operating temperature it becomes a bit sluggish. Plus black smoke or soot in exhaust.
Yea when it’s cold it runs weak at throttle snap and i changed the plugs cause they were slightly black and the bike had a bad hiccup every so often I’ll play with the adjust and see what helps let me know if u have other ideas please
What’s your carb setting? Jets (sizes), needle (is it an adjustable needle), also check float height, diaphragm on slide ok?, accelerator pump..
Hey where did you get your dual gauge for speedometer/ rpm? And where did you get your rpm from?
I got the bike with tach on. Previous owner must have gotten it from a dyna sport glide. Not sure where it gets it from.I would assume from the ignition module
I'm bought a carb from Amazon and it is not working. I can barely get my bike started. A 1996 flstc. I'm at 900ft above sea level and want to know what the recommended keys would be so I can fix this bike. What would you recommend? BTW great video
So you’re looking to fix up the carb you bought from Amazon or your stock Harley one?
@Aron's Garage the one I got from Amazon is a stock one... supposedly. The old one was corroded so bad I threw it away. I think the carb I bought on amazon has the wrong jets. I can get it to turn over and run but only for about 1 sec then it dies. New plugs, new gas and I've got great spark. Ijust think whoever built this damn thing out the wrong jets in it. The mixture screw was only turned out half a turn. I started at 1 3/4 and moved out 1/4 a turn and I'm at 3 turns and still the same. I think the main jet and pilot jet are the wrong sizes.
I’ll be honest with you, I wouldn’t trust that aftermarket carburettor. Your best bet is to get a used genuine one from eBay and refurbish it.
Given yours is an Evo, going with stock jets is recommended ( I believe 42 slow, 165 main?) plus the 88 Sportster needle with a couple of shims. You should be all set with that setting.
I started with 2.5 turns out the bike felt like it was starving for gas a little.
Then I turned them 2 1/4 turns out the bike didn’t seem like it was running on all cylinders.
Any suggestions??
You got leaner as you turned it 2 1/4. Go to 3 turns out or more especially if you have open pipes and high flow air cleaner.
I have now put in a 45 pilot jet. With engine warm and a little high idle rpm(do not have a meter) it doesn’t change rpm, no matter where i have the mix screw, even fully closed?
It responds fine when i rew it
Is that a 88 Twincam? Your rpm will need to be no more than 900 so that you can really notice the change. Once warmed up, bring idle down nice and slow and try again. But even with higher, with idle screw fully in it should stall
I closed my air/fuel mixture screw but the bike did not shut down. Is my carb need to be replaced?
No, you don’t need to replace it. Just check your slow jet (probably too big) > most common cause, or your float level is too high, or the tip of your mixture screw is broken off or damaged..
watched this video yesterday turned the bike on today and it sounds weird tryed to start over and retune but the air fuel mixture screw dosent do nothing to the bike now
If you set it back to where it was, you shouldn’t have issues. What was your setting prior to trying to fine tune it?
How long do you have to warm it up to reach the normal idle?
Best to take it for a 15-20 min ride to bring it up to normal operating temperature. Then you can do the fine tuning.
I like 4:10 horse galloping idle sound! Rich or lean condition ??
I know, I like that too! In this instance it was lean but you can achieve a similar sound if you set the mixture properly or a bit richer then normal, and bring the idle down to roughly 800 or lower. The only thing is that it won’t have idle when engine is cold..Also, on Twincams proper idle oil pressure is achieved only over 900 rpm, so might not worth the risk..
@@aronsgarage834 Thanks. My bike Crane HI4 ignition perfect 850-900 horse galloping idle sound. Crane 15 year old, and dead. New Dyna 2000i ignition want galloping horse sound.
My Dyna has similar when it’s cold around 800 but as it warms up it gets to 1000.
Any advice for no idle and choke not helping?
Could be any of these things. Blocked slow jet, blocked orifices, air jet, improper float level, air leak by manifold or exhaust. Check spark plugs as well to make sure they are not fouled.
@@aronsgarage834 I had also noticed that I had a brand new carb and was getting no fire from the engine. I was getting fuel and spark. But no fire. Swapped for my old carb and it started up with no idle. The issue with the new carb could that be related to intake/ exhaust leak
I wouldn’t think so, otherwise it also wouldn’t work with the old carb. It might be worth taking it apart to make sure all jets are clean and set properly.
How do I now it's in the right place
When you get it to the spot where it’s idling smooth with the highest rpm. Blip the throttle should drop back down easily. If it hangs a bit, too lean. If it drops quickly below your idle and then slowly recovers to the right rpm, too rich.
Other than that, test ride it. Check how it responds, rides cold/warmed up and make further fine adjustments 1/4 turn each time until feels/ rides perfectly.
I just put back in the carburetor it had redone I got it all in and I reved it avd it choked out
@@aronsgarage834 ok thanks
Also between 2 - 3/4 and 3. - 1/4 didn’t change idling why 3-1/4 and not just 3 or else? Also you’re at sea level??
Have a great week broooouuu
I’m 80m above sea level.
it’s always better to run it a little richer engine being air cooled. Since then I have actually gone up to 3.5 and 3 and 3/4 and runs even better. It’s a matter of riding your bike and tweak it here and there to see how it runs best.
Have a great week too!!
@@aronsgarage834also much richer mixture will affect my co2 emission ?????
In is rich and out is lean, that’s why it’s called “air mixture “
It’s not an air mixture screw, but fuel mixture. Other motorcycles, more like 2 strokes have air mixture screws.
On this carb, the mixture screw regulates the fuel in the idle circuit, so turning it out you are making it richer
@@aronsgarage834 my bad 👍
Bump your pilot up one.
Tried years ago. Was too rich.
Thx buddy