Just put ram air on my Eliminator 125, now a question

Discussion in 'OT Driven' started by AVengeance, Oct 11, 2009.

  1. AVengeance

    AVengeance Active Member

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    I just finished putting a block-off plate over the original hole for the air intake (replacing a rubber 90° piece that grabs air from under the seat), cutting a hole facing forward in the air filter housing, and inserting a computer chassis cooling fan funnel in the hole. As vehicle speed increases, air pressure inside the airbox will increase over atmospheric, making it very little work for the engine to draw in air. I also plan on swapping out for a little bit lighter, louder, and freer flowing muffler in the future.

    With the airflow increases, I'm no doubt going to need to enrich the carb a little. I'm used to working on automotive carbs, and thought I'd find one or two mixture adjusting screws in this carburator. Unfortunately, I can find no such thing. How in the world do you adjust this kind of carburator?

    Thanks.


    edit: pic
    [​IMG]
     
    Last edited: Oct 12, 2009
  2. Junkie

    Junkie re-tarded OT Supporter

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    you raise the needle and put in a bigger main jet
     
  3. AVengeance

    AVengeance Active Member

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    Okay. I've seen on the KawiForums Ninja 250R board, where someone would get a new exhaust, then either get a "jet kit" (whatever parts that has in it) or "shim the needle" or "shiim the jet" or something like that, by putting a washer somewhere.

    The service manual says what "number" the jets are. So is bigger bigger, or is smaller bigger? (I'm guessing bigger is bigger). What does the number mean ? On CycleParts.com, the '09 BN125 has main jet listed as #A125, but also has optional main jets listed (#A-130, 120, 122.5, and 127.5). Each one is all of $8. Could this be as easy as pulling the carb and spending $8 on a jet? What is the purpose of "raising the needle" and how is that done? I don't see corrosponding optional parts to the optional main jets.

    Last question: what about an aftermarket fuel pump? I had an old '77 or '78 Dodge Aspen (225 Slant Six!). Ran like absolute crap. Cleaned the tank, filled it with E85, ran it through to clean the crap and age out of it. Changed very gummed up fuel filter. Then, I blocked off the OEM mechanical pump and installed a frame-mounted electric fuel pump. Bumping the pressure up (and making it steady, instead of it fluctuating with engine speed) provided more fuel flow and better atomization. It not only made it run like it was 10 years newer, but it started quicker, and gave it better gas mileage, too. Any chance I could put an aftermarket fuel pump on the bike? These use engine vaccum to pump fuel, right? What about bypassing or supplimenting fuel supply with an aftermarket 4psi or 7psi electric fuel pump (http://www.summitracing.com/parts/PFS-10701/)? I realize that places a load on the electrical system, but I can negate that by using LED and HID lamps to reduce other peripheral current draw. I could also install a potentiometer to be able to "tune" the fuel pump... might this work? Am I in completely uncharted territory? What fuel pressure does the OEM system operate on, on a bike this small?





    Thanks again.

    BTW: totensiebush, Your bike got STOLEN!??!?
     
    Last edited: Oct 12, 2009
  4. Junkie

    Junkie re-tarded OT Supporter

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    My KTM got stolen on 9/18, out of my parents driveway, while I was asleep with my window facing the driveway open.

    I would guess your bike doesn't have a fuel pump and just relies on gravity feed, that's true of most simple carburated bikes. Vacuum simply opens the petcock so that the fuel can flow, which means you don't hydrolock your engine if your float needle goes bad.

    Bigger is bigger. It's the diameter of the needle, in some unit that I don't know. The main jet pretty much only determines wide open throttle mixture, though. The needle controls midrange - raising it = more fuel. The idle jet and idle mixture screw (aka fuel screw, the only externally adjustable thing but it's plugged from the factory) determine mixture at very small throttle positions.
     
  5. AVengeance

    AVengeance Active Member

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    Way more detail, thanks :bowdown:
    I think that all makes sense.
    Because there would be no ram air effect at low speed, I don't think I'd need to mess with anything that determines low speed or low-load mixture. So... step up one jet, and raise the needle would be a good place to start? I can monitor exhaust gas temps at the engine, so cooler = richer = not going to burn a hole in the piston. I can block off the ram air scoop and unblock the OEM inlet to get baseline readings. I could also hook up a vacuum/boost gauge, but I'm not sure if what I have is precise enough to get "boost" readings from the very minimal increase over atmospheric that may be created by the ram air effect. Again, I'll swap block-offs first to get a baseline.

    The other idea for solving the fuel issue I was having was from my race car. I had to use huge (30 lb/hr.) injectors because of the use of ethanol fuel, but it would idle like crap. To improve idle, I hooked up a vacuum-controlled FPR. That way, under high vacuum, fuel flow would be decreased. As vacuum went down (load went up), fuel pressure would rise, flowing more (and atomizing better) per millisecond of on-time for the injectors. Would I damage the carb by using a small fuel pump and FPR? The lowest pressure I can probably get in a pump is 3-4psi. I don't want to add a bunch of hardware (weight, complexity) but if it produced better atomization, fuel ecomony would go up- or at least not DOWN- and performance would be improved.
     
  6. Junkie

    Junkie re-tarded OT Supporter

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    I can't imagine a fuel pump would help at all.
     
  7. AVengeance

    AVengeance Active Member

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    fuel pump = $40 + engineering and time to install it
    jet = $8 + time to install

    I've read the FSM inside and out, and it doesn't give much in the way of how to correct a lean or rich condition. When you say "raise the needle" what do you mean? Do you have a how-to that you've looked at that helps explain (even if not for my bike, but same in concept).

    No other geniuses wanna jump in here? LOL!


    I saw a nice, chromed-out bike a few weeks ago, while at Subway after being on the water for a few hours. Somehow, a big sub is the best food after wakeboarding. Anyway... so this big chromed out cruiser had a much fancier version of what I just put on the Eliminator. Only this thing was chrome and had a butterfly in it like a carb or throttle body (or those bigass supercharger air scoops). I've been looking for such a thing online and can't find anything. I wish I'd thought to ask the guy about his bike when I was there, but I was wore out, looked like a drowned dog, and had by kids with me :rofl: I didn't see it when it was running, only parked, so I'm GUESSING that it was functional, and not some goofy decorative thing.

    edit:
    a-ha! It's called a "hypercharger"! I was looking for "ram air" or "cold air intake" or whatever... finally found it.
    "Kuryakyn Hypercharger"
    [​IMG]

    Of course, my ram air funnel was free, left over from a computer case. For a few more bucks, I could paint it silver :rofl: nah....

    Also, if this thing sticks out further into the airstream than the bike otherwise would be, then it's creating more drag to produce the effect. In my case, the Eliminator is not really any less aerodynamic than before.
    The one thing I do like about this aftermarket thingy is that the butterflies supposedly operate on vacuum. Nifty.
     
    Last edited: Oct 12, 2009
  8. AVengeance

    AVengeance Active Member

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    update: okay, ran the bike last night, and apparently, it works... all too well.

    Below 35mph, the bike seems to have quite a bit more "pep". It acts at low speeds like it acted before swapping the rear sprocket for a "taller geared" (small diameter) one. Above 35mph, though, actual boost is obtained all the way to and into the carb. (I don't mean like a 14psi turbocharger, just > atmospheric). This causes a loss of vacuum, which stops fuel from flowing! The bike would cut out intermittently unless I put my hand over the intake funnel. I didn't think at the time to turn the fuel to PRI, which I think would have allowed fuel to flow regardless of engine vacuum. I just drove it back at 30mph :hs: Looks like I either have to put a restrictor plate behind the fresh air intake (or a spring loaded throttle plate that could be lifted by air force or vacuum), add a device to generate vacuum, or add an electric fuel pump.

    Truly fascinating.

    I think I might try the electric fuel pump first. Just need a safe mounting location for it.

    Seems like quite an ass-backwards design to make fuel flow stop when there's no vacuum. Explains why the bike has no guts at 55mph, though. Throttle all the way open == little to no vacuum = little to no fuel flow when it needs it the most.
     
  9. GammaRadiation

    GammaRadiation Active Member

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    On a carb meant for gravity/vacuum feed, I'd keep the fuel pressure WAY down.
     
  10. AVengeance

    AVengeance Active Member

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    Haha... I think you're right. I did find a little vacuum pump that might do the trick. It's about the size of the micro fuel pump. It would be wired for igntion on (oil pressure on if there's a way) and would overcome the problem of choking for fuel at low vacuum / positive pressure.

    I just ordered the pieces that cosmetically contain the evap canister (Cali only, and I ain't in Cali). Since my bike didn't come with these parts, I can add them, and put the fuel or vacuum pump inside, so they're protected from the elements and it looks closer to stock. If the experiment is a failure, I'll just use the area to store a tool pouch or tire repair kit for the bike. (below, 14091/A and associated brackets).

    I wonder how much pressure can build up in the tank when it gets hot? It's supposed to vent, I know, but when I pull the cap off my Ninja, I can sometimes hear/feel a slight "release". Don't remember specifically about the Eliminator... but any pressure build-up while riding would be transfered through the fuel system as if it were fuel pressure from a pump... but only a very small amount of pressure, I'm sure. I don't think I'd go over 4psi with a fuel pump I might add to the Eliminator.



    [​IMG]
     
    Last edited: Oct 13, 2009
  11. Junkie

    Junkie re-tarded OT Supporter

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    I mean literally raise the needle. if the carb is like most motorcycle carbs that I've seen, there's a needle on a vacuum slide. shim the needle up a mm or two.
     
  12. AVengeance

    AVengeance Active Member

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    I want to get this straight, so I understand (used to fuel injection). This vacuum slide moves the needle when there's more vacuum (lower load) to restrict fuel flow, and moves the needle when there's less vacuum (high load) to allow more fuel flow.

    Do I have that correct so far?

    Okay, next: Is the needle already shimmed with a washer from the factory, or is it "net build" with no existing spacer? I can find washers/spacers of any imaginable size, so that shouldn't be an issue. What should I use or stay away from- delrin, aluminum, stainless, etc.?

    And one last stupid question: if there is positive pressure in the fuel system (4psi from a fuel pump) could this cause problems with forcing things open and allowing too much fuel?


    Thanks again by the way- you've been a huge help!
     
  13. Junkie

    Junkie re-tarded OT Supporter

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    The vacuum slide's default position is down, when there's vacuum across the slide it moves up. In other words, when it restricts airflow it moves up. Up = needle moves out of the hole = more fuel.

    I don't know what would have issues as far as material goes, it's exposed to a tiny amount of fuel. Stainless would be a safe bet. My guess is that there's no existing spacer, but there might be a thin one of some sort. It's also possible that there's a circlip on the needle and that there are multiple positions it can be placed in, if that's true then you can move the circlip instead of shimming the needle.

    As far as the fuel pump goes, my guess is you'd have to lower the float height to get it right.
     
  14. AVengeance

    AVengeance Active Member

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    I've heard a lot of talk on the 250R forum about "shimming the needle" and the Eliminator and 250R use same brand and probably similar model carb (or carbs in the case of the 250). I don't think I'll find the circlips you're talking about.

    I was able to find a 1 to 4 psi FPR, so using a fuel pump becomes a possibility. If I can adjust it to just 1 or 2 psi, the float should be able to cut off fuel when the bowl is full as it should. I'm only going to add a fuel pump if I absolutely NEED to.

    If it's a vacuum issue (loss of vacuum making the fuel supply get cut off at the fuel tap), a small vacuum pump can be added to supply vacuum to the fuel tap. Added electrical load is easily offset by using an LED tail lamp.

    [​IMG]
    $52.00

    Once I get the fuel flowing properly, I'll start worrying about jetting.
     
  15. Junkie

    Junkie re-tarded OT Supporter

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    I'd go with a vacuum pump over a fuel pump any day of the week.
     
  16. AVengeance

    AVengeance Active Member

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    Yea. The vacuum pump (if that's what's needed) is minimally invasive. I'll know if that's what's causing the fuel cutting out as soon as it's not raining.
     
  17. Subie Driver

    Subie Driver Eye see what you did there.

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    This is going to hurt your quest for 100 MPG, you know.
     
  18. GammaRadiation

    GammaRadiation Active Member

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    Wrong bike, you know. :)
     
  19. AVengeance

    AVengeance Active Member

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    Ahem, yea, what CBFryman said. Hell, with this bike I'm asking the impossible. I want 70mph! My unstated goal is to stay above 75mpg. Right now I drive mostly 55 on the bike, and it gets a tad over 80mpg. I don't even want to really ride it at 70 all the time. I just want the bike to have a little more power and be able to get up to 67-70 if I need it to.

    This bike is for my wife, and she doesn't want to ride it if she can't do 70 when she needs the speed (passing a car that's slowing to exit the highway, for example). My wife's commute is shorter than mine, and most of her driving will be around 45mph, which that bike can do all day long. I've already got a smaller dia. rear sprocket on the Eliminator, so the "potential" top speed has been raised. Now I just need a tiny bit of extra power to make sure it can be done on a flat surface with neutral wind. Is that so much to ask? :hs:
     
  20. Raider007

    Raider007 om nom nom nom

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    you're modifying a 125?
     
  21. AVengeance

    AVengeance Active Member

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    Why risk breaking a $7,500 bike, when you can conduct the same kinds of experiments on a $2,500 one of similar design?


    question to all: since rejetting the carb is going to be an absolute must (regardless of other mods that need to be made to use the fresh-air induction), where can I find a bag-o-jets for my carb?

    It's a Mikuni 4stroke 1bbl.

    [​IMG]
     
    Last edited: Oct 15, 2009
  22. GammaRadiation

    GammaRadiation Active Member

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    I modified a 39cc go-ped. :rofl:
     
  23. AVengeance

    AVengeance Active Member

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    Zombieland Rule #32 (or was it 33?): Enjoy the little things


    I'm pretty sure I've found a source on the parts I'm likely to need. I think between limiting the diameter of the fresh-air intake, and/or using a springloaded trap door, combined with swapping for a bigger main jet and raising the needle, I can accomplish the goal of making it run right with additional air.

    Now watch, the Eliminator's aerodynamics are so bad, I'll have the gas mileage down to below what my Ninja 250R does... but hey, at least it'll be able to go 75mph!!!! :rofl: Success!!!!
     
    Last edited: Oct 15, 2009
  24. Maliboost

    Maliboost New Member

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    first off you need to match your float bowl pressure to intake pressure, just connect your float bowl vent to your intake box and get a fuel pump off almost any carbed bike, they should already be regulated to 2-3 psi, i see them on ebay for 10 bucks
     
  25. mtnbikekid08

    mtnbikekid08 Aime-moi moins, mais aime-moi longtemps

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