Jetting advice: CPR air filter on 950

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by randel, Sep 7, 2012.

  1. buzybraza

    buzybraza Been here awhile

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    #21
  2. Sporting Wood

    Sporting Wood I

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    Do you have a dyno chart with afr too or is this a predetermined outcome?
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  3. Navin

    Navin Long timer

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    Moose, sounds like my experience with the K&Ns. Good for you. Ken's advice to me was that the bottom stuff should be close and the mains very lean. Exactly my findings and the bike carburated far better with a snorting pull to the limiter with the 170s or thereabouts. I expected to need to rejet everything over and over but the mains really did the job. :freaky
    #23
  4. mousitsas

    mousitsas Long timer

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    When it comes to AFR, I only trust measurements taken on the road with a good tool and when it comes to power, I only trust my butt. Dynos are very good for tuning a bike to run on them.
    By the way, had a longer ride yesterday, actually low end and midrange might as well be stronger than the prefiltered setup and also smoother, definitely more crisp. No vibes anywhere. The trick with H2W is not the prefilter....it is the bottom jetting.

    I sense you want to prove that something which is not rocket science actually is.
    Similar to the 'you need vacuum' for crisp throttle response fixation going on for years in advrider, an opinion widely popular within 'the experts'
    #24
  5. mousitsas

    mousitsas Long timer

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    Finally I chickened out with the K&Ns Navin and went to the original airbox and snorkel. The rear intake positioning does not allow a clean solution on the SE due to the proximity of the seat pan and filtering surface area becomes problematic. But I had a couple of ideas for an alternative airbox which I will revisit later in the year.
    #25
  6. Sporting Wood

    Sporting Wood I

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    Guy, I was trying to help you... Thats ok. Ride your own ride.

    FWIW, as I indicated in an earlier post, I did a tremendous amount of r&d with this, and with an onboard wideband too. I have ran what you are running, I have logged the results from sea level to 6000'. I know exactly whats going on with your mix, and what the airjets are doing to the midrange, which ones give the better results and which ones don't. Cold hard numbers, not a butt impression...

    Here's the problem as I see it. There is no shortage keyboard genius know it all's that will post as an 'expert' to every thread regardless if they happen to have a clue or not. Some do it so long around here that they actually pick up a shred of knowledge which reinforces their self image as bike guru extraordinaire. Thing is though, without a background of real experience or professional education in this stuff, these guys are often wrong, misleading and post information that's unhelpful to the reader faced with picking out a hidden nugget of gold in a mountain of obfuscated cow shit. I'm only posting information I know to be factual, writhed from 6 years experience with these carbs and 30+ years of tuning and development.

    From your posts, you're saying that you bumped your mains, put the snorkle back on and viola, its just peachy now. That's great! Consider this, you may have had a fat girl with a sloppy gash...traded her in on one a little better looking, but still a little heavy and her tits not so big, and think you're on the top of the world now. Paulina Rubio came knocking at your door and you aren't answering, because you're elbow deep in bed with this chunky A cup girl who you've convinced yourself is the best you can ever do. You hear the knocking, she's right there and you're yelling through the door, 'Fuck off, this isn't rocket science. You experts were all wrong'. She turns around and leaves you to your chubby lover, muttering, 'WTF is this guy talking about...why do I even bother'.
    #26
  7. bruceca2002

    bruceca2002 Been here awhile

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    What would be the optimum jetting for my mostly stock SE950. 2 into 1 pipe with an Acra silencer with spark arrestor. All pollution equipment removed and needles moved up one clip position. I get no popping on deceleration but it only gets about 30 mpg. How many turns out should the fuels screws be set at? The bikes runs very well as is but goes through a lot of gas. Thanks, Bruce
    #27
  8. mousitsas

    mousitsas Long timer

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    Peace SW, it all is ok! :freaky
    Point is that cool hard numbers have nothing to do with what we are talking about. For me in jetting, all I want numbers for is when it comes to mains to not run lean (or very rich) on the top end. But KTM did the work for us here, by setting the ballpark. Also you and H2W and K2M did a lot of wideband work, I acknowledge that and gave us a nice running low-midrange. From there on I really don't think I need any numbers, I only rely on my feeling of what a nice running engine should be like. And if the two are in dispute, I would always tune to what feeling is telling me.
    #28
  9. mountain eagle

    mountain eagle terrorist

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    Fat girls need love too.............. :rofl
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  10. randel

    randel Been here awhile

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    Thank you all, a lot of valuable information!
    As a conclusion, I thought about following setup going from H2W prefilter setup to CPR filter when it arrives:

    Main Jets 175/175 front/rear
    Idle Air Jet 50
    Mixture Screws 2 turns
    Float Level 4mm
    install Factory Pro needles (I have FP kit), 3rd clip?

    Did I miss anything?
    #30
  11. Sporting Wood

    Sporting Wood I

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    Good starting point imho. I like the 2nt clip on my bike, but they all seem to respond a little differently. If its rich on the bottom end, of if it bogs down when you suddenly open the throttle, drop her down a notch...or turn in the screws a bit...or lean the bowls more... Raising the needle smooths the transition from slow jet to main, but there tends to be a lot of bleed through with the CVRs, soaking the bottom end and I find it easier and better to leave the needle in 2. It is all about creating good throttle response and an even transition from slow to main jet...and there are several ways to do this.

    I'll report back once I've got some time with it and we'll compare notes.


    I don't have any experience with the 2-1 pipe but it would seem you are too rich where you run it most. Sort of to reiterate what I said above. If you were stock and only raised the needle, you have smoothed the transition zone, the 4000 rpm range where they like to cough and sputter out lean... but you have done so at the expense of enrichening your bottom end. Either turn in the screws, or lean the floats...or both, or drop the needle back down and attack the tune by first fixing the top end lean condition with bigger mains. This will also flow more fuel to the bottom and the transition. Lean the floats a mm and turn the screws to about 1.5-2 turns out. I'm not a fan of the stock needle but it can work this way.
    #31
  12. Sporting Wood

    Sporting Wood I

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    :freaky

    [​IMG]
    #32
  13. Sporting Wood

    Sporting Wood I

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    Update, I really like free flowing air. 175 mains, 42 slows, 1 3/4 turns on the screws, leaned float by a mm, 87 octane, fp needle @ 2. Runs great from 800' to 12,000...prolly good under 800', didn't get that low yet. It roars, makes plenty more power.

    I can up the mains from this easily, I was worried going to Colorado that it'd be too fat.

    Rolled my own filter out of a scrap of 1/8" alloy and some buna grommets that hold it firm to the carb base. Bought the same itg filter as the cpr guys use...best $80 mod ever :D

    [​IMG]
    #33
  14. Grinderman

    Grinderman Been here awhile

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    Thanks so much sporting wood!! I am going from the h2w setup to the CPR. 2 questions for you. We only want the 42 pilots?? Why not the 45's? And second is easy. I want to mimick your FP setup with the needles. 2nd position is from the top down or bottom ( pointy end) up? Thanks in advance for helping out.
    #34
  15. mousitsas

    mousitsas Long timer

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    I am not really entitled to answer, as I don't have a CPR box, but I have gone from H2W to a DNA filter + sommers door mods, which flows similarly with the CPR at least for small throttle openings. What I found, is that to eliminate popping on deceleration I had to turn the fuel screws 3 turns out which is more or less the limit of their adjustment range on the rich side and still pops a tad, but goes much better than H2W. I only touched the fuel screws and the mains going from H2W to DNA. So, I would suggest if anything to fatten up the jetting in this area if you change to a free-er flowing setup, but that might not be necessary.
    #35
  16. Sporting Wood

    Sporting Wood I

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    Mains bleed fuel into the throat, big mains bleed more counteracting some of the need to fatten the low end.
    No 45's because I find them too rich at altitude...and I'm on my way back from freaking Colorado! I did get them to work at home well but the climb up to 4-5000' always revealed that the bottom starts to choke. I want it to work everywhere and return good mileage...even at a loss of some power...though 45's absolutely rock at low elevations... 3rd gear wheelies!

    2nt leanest clip btw, not from the pointy end. I find the 3rd bleeds more fuel into the low circuit, complicating getting the bottom to run well. Fat mains multiply that problem. I get good throttle response, no hole at needle opening so I see no reason.
    #36
  17. Grinderman

    Grinderman Been here awhile

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    Awesome!! Exact info needed. Appreciate it guys!
    #37
  18. Sporting Wood

    Sporting Wood I

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    Frankly, there's a reason I didn't buy the CPR to do this.
    #38
  19. Grinderman

    Grinderman Been here awhile

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    O.k. I put in the fp needles at position #2 with the big washer/spacer on top and the skinny little one on the bottom. My float height is right around 3.5mm. 42 pilots. 175f and 178r on the mains. I would have made them the same but I didn't have 2 175's. And the result was.....Crap! Bike was flat as a pancake in the top end. Wasn't snappy at all off the bottom. In all my previous setups I can power wheelie in first and 2nd. This one was dead. I don't think the answer is bigger mains. I ran a 175/180 setup previously with the stack needle in position 3 with the float much higher into the bowl (leaner, correct?). It pulled pretty well at those settings but of course I always WANT MORE! Help me please.....
    #39
  20. Sporting Wood

    Sporting Wood I

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    Every bike is different, gas varies, altitude, expectations, etc... Sounds like you had it pretty good last setup. I'd go back to that if it was me. Small adjustments from there.

    Was it factory needles, factory airjets, airbox, etc? If you had it with the h2w kit, the airjets should be different... and no way would it have run on those big mains.
    #40