Jetting, Dyno Tuning, AFRs??? Help A Jiglet Out

[Jiggles]

Aight @chodette and @alexis, I turned the idle screws in making it leaner because my bottom end is richer than mitt romney, 1 turn in (2 turns out) made it run worse so I tried 1 turn out on both and it the revs got so low the engine died. So I turned the idle knob up and put the screws all the way in to just start from base. 1 Turn out on each, running ok, 2 turns out, running good, 3 turns out running even better, but we know that 3 turns out is too rich, so I put it back to 2 turns and adjusted the idle knob to an appropriate level.

Do you suppose its possible that at idle (uncheckable as of now by AFR tool) I'm actually running lean but then once some throttle is applied it shoots way off to rich? Whats the course of action here???

[flynjay]

What is making you think that 3 turns out is too rich?

I would surmise from your post that you are actually too lean and need to keep turning the needle out (CCW) until you get a drop in RPM, then go in 1/4 turn.

Sounds like you need to go up a pilot jet size.

[alex.s]

Originally Posted by flynjay

What is making you think that 3 turns out is too rich?

I would surmise from your post that you are actually too lean and need to keep turning the needle out (CCW) until you get a drop in RPM, then go in 1/4 turn.

Sounds like you need to go up a pilot jet size.

this.

also,

they call me lexi. not alexis.

[choneofakind]

Jig, small changes dawg!! Like only 1/4 turn at a time. Start at 2.5 turns like stock, and try going out in 1/4 increments as needed.

[Jiggles]

Originally Posted by flynjay

What is making you think that 3 turns out is too rich?

I would surmise from your post that you are actually too lean and need to keep turning the needle out (CCW) until you get a drop in RPM, then go in 1/4 turn.

Sounds like you need to go up a pilot jet size.

The dyno at the top is with the screws out 3 turns, so its too rich

Originally Posted by alex.s

this.

also,

they call me lexi. not alexis.

Didn't you say go down a pilot jet because its too rich?????

Originally Posted by choneofakind

Jig, small changes dawg!! Like only 1/4 turn at a time. Start at 2.5 turns like stock, and try going out in 1/4 increments as needed.

Lol fine, so you think I need to go richer?

[choneofakind]

You were too rich. Then you went too far and went lean. Where are you now? Make one small change at a time yo! you'z makin newbie mistakes.

[flynjay]

Originally Posted by Jiggles

The dyno at the top is with the screws out 3 turns, so its too rich

1. They dyno run is really only showing you what the main jet is doing since you should be at WOT for the whole run. (I could be wrong on this as I've never played on the dyno).

2. The start of the dyno run is too lean (High AF ratio).

Keep turning the idle mixture screws CCW 1/4 turn at a time with the bike running until the rpm stops climbing. Then turn CW 1/4 turn. Then adjust your idle to ~1500. That should be about right at idle.

[Jiggles]

Originally Posted by flynjay

1. They dyno run is really only showing you what the main jet is doing since you should be at WOT for the whole run. (I could be wrong on this as I've never played on the dyno).

2. The start of the dyno run is too lean (High AF ratio).

Keep turning the idle mixture screws CCW 1/4 turn at a time with the bike running until the rpm stops climbing. Then turn CW 1/4 turn. Then adjust your idle to ~1500. That should be about right at idle.

The start is innaccurate because there is not enough exhaust gas flowing. It was reading 21-22 AFR

I did the quarter turn thing (starting from all the way screwed in, wanted to be sure) and I ended up at 3 turns, then alex and chode both said its too rich and I need to screw it in more or go down a pilot jet

[choneofakind]

Ugh, so it was rich at 3, but hanging at idle on 2.5? try 2.75...

[Jiggles]

Bah, I'll **** with the idle when I get the AFR guage installed

[Jiggles]

Ok so I took the bike out, top end and midrange is feeling pretty damn good but low end under 5k runs like **** haha. It is hanging when reving down and there is like 0 power until 5k. That's indicative of too lean right right?

[flynjay]

Don't give up now. People have been tuning carbs without AFR and dyno's for decades. It just takes some practice.

Keep turning the needles 1/4 at a time. As a check rev it up and watch how the rpm's return, if they hang high it's still lean, if the drop below it's rich.

[choneofakind]

yes. Bring the mix screws out 1/4 turn.

[Jiggles]

Originally Posted by flynjay

Don't give up now. People have been tuning carbs without AFR and dyno's for decades. It just takes some practice.

Keep turning the needles 1/4 at a time. As a check rev it up and watch how the rpm's return, if they hang high it's still lean, if the drop below it's rich.

All those people were idiots!

Originally Posted by choneofakind

yes. Bring the mix screws out 1/4 turn.

Fa sho. It ran good at 3 turns out, I'm at 2 right now. 3 turns was apparently rich but it idled the best at that. Guess Ill do some of this quarter turn nonsense

Oh and my off set screwdriver broke a tooth off. Isn't that nice

[choneofakind]

I took a bicycle tool apart and use the flat-screwdriver from that. Works well enough for me that I suggest buying a $2 bike tool from wally world and taking it apart for you carbs.

[Jiggles]

It still works it just gets a little stuck on the broken tooth. I have to force it a bit and will likely end up breaking it some more I already ordered a new one though, will be here on thursday, AFTER I need it

K soon as I finish this sammich I'ma go do this! In the DURK!

[Jiggles]

Ok, so I started from 2 turns out and went by a quarter turn all the way to 4 turns and the low end is all poop, even though it wasn't this bad before at 3 turns. I've since gone up 2 sizes in the jets and gone up 2 clip positions on the needles, then I decided to tune the idle and it seems like no matter what position the screws are at its always lean (this is lean right?) I ordered the next size up pilots #40 but they won't arrive before the dyno

Here's a vid of how its running right now just to confirm that I am actually too lean

Link to original page on YouTube.

[menikmati]

dat last pull...

need mo' brap brap.

[jeffreys24]

Could be a vacuum problem. After I re jetted mine it ran awesome from 4 thousand to to the limiter but had a bad hang going back to the idle. I had a vacuum line routed wrong. You could check your lines and check to make sure there not cracked.

[Jiggles]

Hmm, do you recall which one?

[jeffreys24]

No I don't recall. If I where u I would find the diagram and check your hoses though. That's how I found it. If it is your problem you could mess with the mixtures screws all week and get nowhere. As soon as I figured it out it ran awesome at 2 3/4 turns out and dropped right to idle.

[Jiggles]

What mods do you have?

[JA-Moo]

I would say you are trying to tune the wrong circuit. The "idle" circuit which consists of the pilot jet and fuel screw, is basically only for your idle mixture. When adjusting your fuel screw, it should be turned in and out until you get the highest idle. What that means is you have the best air/fuel mixture for idle. And that circuit is done, no need for any more adjustment.

In the vid, it sounds rich, as the motor is studdering, where as a lean mixture would cause a flat response. That would be either your needle position, spring tension on the slides, or the air bleed hole size in your slide.

And it is a misconception that a dyno run is just sampling your main jet. As you are rolling on the throttle, it is sampling the air/fuel mixture in your low/mid rpm section (needle/needle jet) I equate the needle/needle jet with accelerate pumps on older cars and carbed hot rods. As you roll or whack open the throttle, the fuel/air coming in has to be the correct ratio. Just as the accelerator pump adds a lot of fuel when throttle valves are opened up letting in a lot of air. If your needle/needle is incorrect, either the motor stumbles trying to burn too much fuel, and doesn't fire every time it should, or if it's lean, there is not enough fuel for each combustion cycle and the motor runs flat like you are running out of gas.

Get the idle circuit correct, then work on the needle position.

[jeffreys24]

Slipon 2 brothers. Snorkel removed. Dynojet kit. Pipercross air filter.

[Jiggles]

Originally Posted by JA-Moo

I would say you are trying to tune the wrong circuit. The "idle" circuit which consists of the pilot jet and fuel screw, is basically only for your idle mixture. When adjusting your fuel screw, it should be turned in and out until you get the highest idle. What that means is you have the best air/fuel mixture for idle. And that circuit is done, no need for any more adjustment.

In the vid, it sounds rich, as the motor is studdering, where as a lean mixture would cause a flat response. That would be either your needle position, spring tension on the slides, or the air bleed hole size in your slide.

And it is a misconception that a dyno run is just sampling your main jet. As you are rolling on the throttle, it is sampling the air/fuel mixture in your low/mid rpm section (needle/needle jet) I equate the needle/needle jet with accelerate pumps on older cars and carbed hot rods. As you roll or whack open the throttle, the fuel/air coming in has to be the correct ratio. Just as the accelerator pump adds a lot of fuel when throttle valves are opened up letting in a lot of air. If your needle/needle is incorrect, either the motor stumbles trying to burn too much fuel, and doesn't fire every time it should, or if it's lean, there is not enough fuel for each combustion cycle and the motor runs flat like you are running out of gas.

Get the idle circuit correct, then work on the needle position.

Ok, so then Idle is totally fine. Do you think the needle would be affecting the range as low as 3-5k? I did bump the needle up 2 clip positions (richer) and I haven't changed pilots yet the low end is crap now where as it wasn't before I moved the needle. So, if the needle does affect the flow that low then I suppose it is too rich, I have a dyno tomorrow at 10:30 so I'll move it then

Oh and I'm having them install an O2 bung so I'm hoping we can just plug the AFR gauge of the dyno straight into my midpipe for a more accurate AFR reading

[JA-Moo]

Originally Posted by Jiggles

Ok, so then Idle is totally fine. Do you think the needle would be affecting the range as low as 3-5k? I did bump the needle up 2 clip positions (richer) and I haven't changed pilots yet the low end is crap now where as it wasn't before I moved the needle. So, if the needle does affect the flow that low then I suppose it is too rich, I have a dyno tomorrow at 10:30 so I'll move it then

Oh and I'm having them install an O2 bung so I'm hoping we can just plug the AFR gauge of the dyno straight into my midpipe for a more accurate AFR reading

When working with jetting, rpm is not a indicator, it is all throttle position. That tells you what circuit is the problem. You should have your throttle marked off in 1/4ths. A bit of tape and a stick pin stuck in the lip of the hand grip for reference.

[Jiggles]

Welp, no matter the throttle setting it ran like poop from 3-5k whether WOT or not.

I'm a bit confused about how this works, lets say I go WOT at 1.5k rpms and it revs up to 3 still WOT, if I were to be checking the AFR, would I only be seeing the AFR of the main jet?



So according to this chart, if I'm at WOT (assume I've been at WOT) would I only be seeing the main jet come into effect like this chart says?

Originally that's how I thought it worked, then I read something that had me thinking that pilots affect low range (0-5k), needle affects midrange (5k-9k) and mains affect top end (9k-redline).

If you can answer this question I think I'll understand If I am WOT at 3k rpms, is the main jet the main factor into how much fuel is delivered?

[JA-Moo]

Originally Posted by Jiggles

Welp, no matter the throttle setting it ran like poop from 3-5k whether WOT or not.

Then something is way off, I can only guess it's your needle height

I'm a bit confused about how this works, lets say I go WOT at 1.5k rpms and it revs up to 3 still WOT, if I were to be checking the AFR, would I only be seeing the AFR of the main jet?

What you are seeing in that bit of time is the the is a combination of the opening mixture and main jet. The Problem is, that you are so low in the rpm range, everything in the system is playing catch up. You are way out of the power band.



So according to this chart, if I'm at WOT (assume I've been at WOT) would I only be seeing the main jet come into effect like this chart says?

That chart is a bit "general", and not for CV carbs. The main jet is usually the only control factor at 3/4 to full throttle. If you are in the power band, then yes, it is showing main jet.

Originally that's how I thought it worked, then I read something that had me thinking that pilots affect low range (0-5k), needle affects midrange (5k-9k) and mains affect top end (9k-redline).

That is incorrect.Throttle position can be anywhere and is not connected to rpm.You can rev to 13 grand at 1/8th throttle in neutral.

If you can answer this question I think I'll understand If I am WOT at 3k rpms, is the main jet the main factor into how much fuel is delivered?

No, you have to take into account, your throttle can be WFO, but if the airspeed is slow, then the slides are lower, thus you will be on the needle.

[Jiggles]

Ok, through your answers and a bit of reading on carbs I have a very mildly vague idea about how this works

When you said if I'm in the power band then yes its showing the main jet, is that because at that point the engine is revving fast enough that it is sucking in enough air that the main jet is the "limiting factor" in how much fuel is being added?

Right now, I think my main is about right or one size too big, I'll see when I get on the dyno. My needle is way too damn high, that is for sure and I think what is causing the problems at 3-5k, its just letting in too much fuel. I'll drop it down to 4th position when I get a chance.

So then Ja-moo, if you look at my dyno, what do you make of that? What would be the reason (its done at WOT by the way) that it goes from an AFR of 10.0 at 3k to an AFR of 16.0 at 6k? And how would I fix that?

And finally, while I have the dyno tomorrow should I test like a 1/4-half throttle rev through the entire range? That would tell me how well the needle is seated right?

Boy learning sure is fun! Maybe I'll just take the easy route and install EFI so the computer can have all the fun tuning the AFR to perfection

[Racer x]

You are getting there.
One thing that is confusing you is wide open throttle just opens the throttle. The slide does not start to move until after the throttle moves then it starts to move according to engine speed.

Opening up the throttle at 3000 rpm will not go immediately to the main jet. So maybe think idle jet from idle to 2000. pilot jet from 1500to 4500, main jet and needle from there. They all overlap.

The idle holes are built into the carb body and throttle plate. Once you open the throttle they are done.then it is pilot jets.
Did the pilot jets come in yet? turning the screws all day will not make any difference once you start to open the throttle. That is why a richer pilot helps with cold running.It gives more fuel with the cold air.
Maybe this will help.

http://www.gadgetjq.com/keihin_carb.htm

[JA-Moo]

Originally Posted by Jiggles

So then Ja-moo, if you look at my dyno, what do you make of that? What would be the reason (its done at WOT by the way) that it goes from an AFR of 10.0 at 3k to an AFR of 16.0 at 6k? And how would I fix that?

Your dyno run is a bit different then the ones I am used to as we usually start at 4000 rpm or higher in 4th or 5th gear. I can't really see how you can get a good A/F reading going to WFO at such a low RPM, as the airspeed and slide is moving much slower than the throttle is opening.

And finally, while I have the dyno tomorrow should I test like a 1/4-half throttle rev through the entire range? That would tell me how well the needle is seated right?

It looks like the dyno is is a dynamic, or rolling road type, so you can't really test part throttle, as it is just sampling how fast the tire is spinning up the drum. For part throttle testing you need an eddie current dyno, where the drum is loaded and is resisting spinning up.

Boy learning sure is fun! Maybe I'll just take the easy route and install EFI so the computer can have all the fun tuning the AFR to perfection

Jetting can get complicated, especially with CV carbs. In my "day", CV's were taken off and VM's were installed, as they are much easier to tune and flow better. But, learning is a good thing, the more the better.

[Jiggles]

I think that it is resisted, it has settings for vehicle weight and stuff like that. They are also capable of recording quarter mile times on it, if it wasn't resisted people would get ridiculously fast '1/4 mile' times right? Idk I'll ask him.

And the dyno is done in 4th gear.

What would you recommend, rev the bike to 4k in 4th and then do a wot roll on?

[Jiggles]

Well my Afr curve is **** right now but at peak I just made 30.5hp. What now bitches!?!?

[JA-Moo]

Originally Posted by Jiggles

Well my Afr curve is **** right now but at peak I just made 30.5hp. What now bitches!?!?

More mods!

[Racer x]

You are lean for safety. Try to get closer to 13. Have you installed the BRT ignition system? What jets are you using?

[flynjay]

If your max afr is 12.2 you are way too rich. at least one jet size. What does the whole plot look like?

[Jiggles]

Originally Posted by JA-Moo

More mods!

Originally Posted by Racer x

You are lean for safety. Try to get closer to 13. Have you installed the BRT ignition system? What jets are you using?

Lean for safety? I'm super duper rich right now

Originally Posted by flynjay

If your max afr is 12.2 you are way too rich. at least one jet size. What does the whole plot look like?

Oh for sure its scanning right now. My poop zone at 3-4k had an AFR of like 8, it was so bad. When I got to the place I switched my needle position from 5 to 4 and we ran it but it still had that crap zone. After the dyno run was finished I saw that at idle my afr was between 11-12 (it would change around in that region) so I adjusted the mix screws in a quarter turn to 2.75 out and when I left, the poop zone was gone! Most likely I'm at the rich limit in that 3-4 zone

[Jiggles]

Originally Posted by Racer x

You are lean for safety. Try to get closer to 13. Have you installed the BRT ignition system? What jets are you using?

BRT ignition system? What is that and why do I want it? Jets are Keihn 118, I could probably stand to put in 115s

Since I changed the mix screws a quarter turn leaner, that lower poop zone is gone, most likely its at the rich limit. My O2 bung and sensor have been installed, I just need to wire up the guage so it turns on

[Racer x]

The BRT igntion system is adjustable. You can add timing at 7000 and take a little away at 9000 going say from 42 to 44 then back to 42. That will remove the flat spot in your curve, Also give more than 7 deg advance at red line raising the HP some more. On top of that you can raise the rev limit to 14000 from the factory 13500. That way you can push the engine a little harder and not hit the factory limiter that comes on to strong.

wait there's more. You have two maps to choose from on the fly with a bar mounted switch.
Before when I said 48 pilots .I ment going from stock 30 to 40. My bad.

[Jiggles]

Well, the BRT sounds sexy as hell, whats the typical price associated with one?