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Discussion Starter #1
I'm on the road right now and was hoping to get the carbs tuned the old fashion way. In goes the towel and a shop is going to try and squeeze me in for a dyno run first thing tomorrow morning, but I want to run my situation by here for any suggestions from this crowd.

I'm running fully exposed(no side covers or anything) K&N pods and short TOR's on an otherwise stock 2003 America engine. I probably tried more jet and needle combinations than I can count with my fingers, toes, and pants down while I was riding between San Francisco and Santa Barbara but I still can't get 'em to behave at crusing speed. The engine starts to struggle around 60mph in 5th so I spent most of my time around 50 in 4th, which is fine in the twisties on the section of CA1 I was on but a great impediment when I'm trying to tick away miles. Gusts of wind can induce this problem too. I can open it up and get past this point but as soon as I let off the engine gives that struggling feeling until I'm slowed back down. I'm running the softer DJ springs(I know the stock springs are one problem that's been discussed a lot here), DJ needles currently on the 6th notch, 138 mains and 45 pilots. No matter which jets I've had in, that problem always shows up at speed, making me think it might be related to air turbulence. I don't even remember how many turns out I've got on this set-up, somewhere around 3 to make the decel popping go away.

Available to me right now I have the stock pilots and current 45s and a plethora of mains up to the currently installed 138s. Stock needles and springs, a few shims, etc. etc. etc. Kind of reluctant to toss around the idea of drilling things out until after I'm back home. I at least know I can make it home at 50 mph this way. Any thoughts?

Roger
 

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sounds like that set up you got now is way to rich should be maybe 40 or 42 pilots try the niddle in the middle slot.At cruse speed the mains dont do that much.They may be alittle big .The only way you will know is to put it on a dyno.tell the dyno guy to check it at cruse speed .
 

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I've been carrying out loads of testing with the standard air box and an AFR meter. I tried running without the left side cover and it made tuning the carbs imposible. The prevailing wind and gusts made a difference to the AFR depending on which direction I was travelling in.

This may or may not be the same with pods, but if it does effect them in the same way you won't see it on a dyno.

Run with your side covers on for a while and see if it settles down.
 

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Roger,

I think you may be too large on the pilot jets and way too small on the main jets (if your main jet numbers are for Keihin jets and not Dyno Jet brand jets). My Dyno man set up an '03 America similar to yours the week before I went to see him--he said he used 147 mains, Thruxton needles, and I believe he stayed with the stock 40 pilot jets.

If one sets the pilot screws rich enough to keep it from popping on decel, it is set WAY too rich, IMHO.
 

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Discussion Starter #6
Run with your side covers on for a while and see if it settles down.
Kinda hard to do that now! :D


Redbird, thanks for that bit of info. I was just going on the 2003 survey info(not much) and had the DJ kit with up to 128 dj mains. I ordered 3 sets of keihin jets up to the 138s and the 45 pilots(I believe the stock pilots are 42's not 40s for the america). We'll see what direction the shop pushes me in after the run tomorrow morning. I'll probably end up ordering up another pair or two of jets to be there when I get home.

mikeinva, I'm pretty sure the wind is part of it. When I hit a strong head wind I had to slow it down even more to keep her running happy. A strong side gust and I can hear the two cylinder are not on speaking terms. Time to fab up some "custom" wind stabilizers?:eek:

Here's my cliche picture from a good day, despite my carb mishaps. I probably spent less than two hours throwing together that sissy bar so I would have somewhere to strap stuff.


Roger
 

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well you know wind will put alot more load on a motor if its blowing in a dir. that trys and slow you down.Its not allways a dead head wind ether any angle from the front of the bike will do that.ITs like putting on the brake .Iwonder if thats part of what some of you are feeling and seeing on a/f gauge.On a dyno with a brake you can change the load on the bike and change the a/f mixture to a degree.I dont know if thats what is happening though.I do think the more power your bike is making the less you feel it slow down in the wind.The harder the motor must work to hold speed the worst it sounds like its running .You can feel and hear it much more on a naked bike.
 

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I really believe it has to do with jetting and not a wind effect per se. I live and ride in Oklahoma and ride in winds of 30--40 mph frequently with gusts even higher. I have never experienced any effect that made me think wind was having any affect on the carburetors. I have read some posts on this forum where riders did say they have noticed a wind effect if it was from a particular direction, but I can't remember if they were riding a 270 twin or a 360 twin. I do keep my side covers on my 360 twin, and I have not tried it without them which could possibly make a difference.

Good Luck,
 

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I'm on the road right now and was hoping to get the carbs tuned the old fashion way. In goes the towel and a shop is going to try and squeeze me in for a dyno run first thing tomorrow morning, but I want to run my situation by here for any suggestions from this crowd.

I'm running fully exposed(no side covers or anything) K&N pods and short TOR's on an otherwise stock 2003 America engine. I probably tried more jet and needle combinations than I can count with my fingers, toes, and pants down while I was riding between San Francisco and Santa Barbara but I still can't get 'em to behave at crusing speed. The engine starts to struggle around 60mph in 5th so I spent most of my time around 50 in 4th, which is fine in the twisties on the section of CA1 I was on but a great impediment when I'm trying to tick away miles. Gusts of wind can induce this problem too. I can open it up and get past this point but as soon as I let off the engine gives that struggling feeling until I'm slowed back down. I'm running the softer DJ springs(I know the stock springs are one problem that's been discussed a lot here), DJ needles currently on the 6th notch, 138 mains and 45 pilots. No matter which jets I've had in, that problem always shows up at speed, making me think it might be related to air turbulence. I don't even remember how many turns out I've got on this set-up, somewhere around 3 to make the decel popping go away.

Available to me right now I have the stock pilots and current 45s and a plethora of mains up to the currently installed 138s. Stock needles and springs, a few shims, etc. etc. etc. Kind of reluctant to toss around the idea of drilling things out until after I'm back home. I at least know I can make it home at 50 mph this way. Any thoughts?

Roger
I have been struggling with the same thing... and like you... came to the same conclusion. Yesterday, however, I had an epiphany.

While I was out riding (logged about 200 miles yesterday) I was again noticing what didn't feel like the engine was cutting out but certainly hitting a slight wall. I could accelerate through it... but at idle it was just... like it was slightly losing power and then returning. I went down a street doing about 65 or 70 and felt it... the wind was gusting head on so I decided to turn around and repeat the trip. If it was the wind... I should not feel the "stutter" right? I did. I know it is a problem with the jets but what I am not sure about is if I am running too rich or too lean.

This morning, on my way to mass, I decided to leave my choke out. While this increased my idle RPM I had no hesitation down the same road and with the wind blowing in my face. This leads me to believe that my current settings have me running FAR too lean.

My current setup:
08 Bonnie Black 865cc
+nark
+tors
42 pilots / 142 mains

I hope this helps you out a little bit Verde... maybe we can help each other through this process.
 

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Discussion Starter #11
Here are the results from her visit with the dynacologist.



Other than the standard runs, he tried to replicate my problem and couldn't. I think he said he used a 20% resistance for replicating wind drag. On my return trip north I did my own wind load test by standing up on the p pegs to see if that extra drag would cause it to start doing it's thing like when a head on gust hits me but no dice. I've convinced myself it's definitely air pressure changes that can only be overcome by stabilizing the air somehow. Granted there is some room to dial in the jetting a bit better, but the main problem has got to be that choppy higher speed air. Some kind of finned pod shrouds are well into the brainstorming process right now...

On that note of dialing in the jetting a bit better... stock pilots, slightly bigger mains, and drop the needles down some sound right?

rob, I feel it regardless of wind direction. Just a slight bit slower or faster before it hits depending on head on/tail winds. I think it's just the aerodynamics around the engine as it gets up to speed which can only be thwarted with air boxes, side covers, or opening up the throttle so much that it sucks in enough air regardless.

propforward, thanks but too bad it's at the cost of performance. That battery box is already a little scuffed from the chain in the picture. Should have gone a 1/4 inch skinnier but It's already so tight inside there it's a rats nest that even a rat would be ashamed of.

Roger
 

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There's a huge dip in a/f that starts at 4000 rpm - could it be that that is causing the problem? It's going really rich there, so that would make it bog down - maybe that's what you are feeling? That suggests a jetting / needle combination problem I think?
 

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from that dyno chart you have way to small of main jets.your a/f needs to be around 13.0 on top end. Your slide is doing some strange things to go that rich in the middle. Did you drill the slides out? sometimes that makes them ack crazy like that.That rich dip only happens when the slide is open to far for what fuel it needs .That can make it kinda bog .being lean on top and bottom is killing you that will give you the dead feeling you have.
 

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Discussion Starter #14
No drilling done. I did notice the DJ needles are skinnier and fit looser in the slides than stock, there by letting some air by and acting like I drilled it out maybe? Are DJ needles the same for 2003 vs 2004? I was told to buy the 2004 kit since that was the eairliest kit offered for the america(as opposed to getting the 2003 bonnie kit) and that I just wouldn't need the D-tool. I did try the stock needles on my trip too and still had the problem though. Can't remember what mains I had in then, I think it was the 138s but may have been 135s. Tried with and without shims.

I'm still on about this air turbulence stuff too... thinking maybe the gusts are causing the slides to blip open or snap closed. That combined with the way they behave with that AFR swing is a total gaggle.

Roger
 

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No drilling done. I did notice the DJ needles are skinnier and fit looser in the slides than stock, there by letting some air by and acting like I drilled it out maybe? Are DJ needles the same for 2003 vs 2004? I was told to buy the 2004 kit since that was the eairliest kit offered for the america(as opposed to getting the 2003 bonnie kit) and that I just wouldn't need the D-tool. I did try the stock needles on my trip too and still had the problem though. Can't remember what mains I had in then, I think it was the 138s but may have been 135s. Tried with and without shims.

I'm still on about this air turbulence stuff too... thinking maybe the gusts are causing the slides to blip open or snap closed. That combined with the way they behave with that AFR swing is a total gaggle.

Roger
Did you try blowing on it while it was on the Dyno?
 

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If you had the dj springs in on that dyno run I would try the stock springs and see what they do. I ran the dj springs in mine it made the slides open much faster maybe yours are opening to fast
 

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Discussion Starter #17
Yeah, DJ springs were in. Tomorrow I'll try that swap and see if that helps.

Haha, rob, no. The shop did have an extra big floor fan I think, oh well. The guy sorta seemed like he knew about as much as me, so that probably didn't help either. He was more interested in trying to give me a lecture about the carbs not being engineered for pods rather than help dial them in.

Roger
 

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Its hard to find a good dyno guy that knows anything about our bikes.I just get them to run mine then go home study the sheet re adjust what i think is needed then go back for another run it can cost you to get them right though.
 

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...That rich dip only happens when the slide is open to far for what fuel it needs ...
Not necessarily; on the stock CVK carbs lighter & shorter springs can induce a transient lean condition if the CV slides open too soon. That happened with my 865/270 from about 2300 - 3300 rpm (with Kawasaki 92081-1760 vacuum springs) which required larger pilots & 2 shims (stock needles) to improve. I'm not saying that is directly comparable to the 790/270 (different cams), but that's what happend on my bike.
 

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Not necessarily; on the stock CVK carbs lighter & shorter springs can induce a transient lean condition if the CV slides open too soon. That happened with my 865/270 from about 2300 - 3300 rpm (with Kawasaki 92081-1760 vacuum springs) which required larger pilots & 2 shims (stock needles) to improve. I'm not saying that is directly comparable to the 790/270 (different cams), but that's what happend on my bike.
Yours was at the transfer point from the pilots to the niddles right? what i am looking at on his is its over 4000rpms it should be past that point you had on yours .what you think? its real hard to say. On yours at low rpm the slides opening to soon you loose vac causeing it to go lean i dont think his will at that high of rpm.who knows.Thats why i love flat slide carbs you know where the slides are at .
 
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