New air filter, 950 now runs funny

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by avocadofarmer, May 25, 2013.

  1. avocadofarmer

    avocadofarmer Fruit Coot

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    I upgraded out of the stock airbox on my 06 to a really sweet ITG filter (like the Rotweiler setup). The bike still has SAS and the stock exhausts. The bike seems to have the hickups at low engine speeds and at cold idle. It sounds like a small backfire and usually stalls the bike if it is idling. It's a bitch to get started when cold, usually requires full choke and multiple ugly starting attempts. Smells quite rich and feels like it is running rich at first (bog off idle).

    The other hickup issue happens when cruising along with very, very little throttle, usually around 3000 rpm. The bike just kinda misses and slaps the chain with a sudden engine movement. Definitely annoying.

    I'm running 175/178 mains, 42 pilot, 60 IAJ, 3mm set floats and I've got the flex jets adjusted anywhere between 1.5 and 3 turns out trying to sort this issue (no flex jet adjustment seems to do much). I'm at about 1500 ft elevation. Bike has recently had the valves checked, 13k on motor. Problem seems to be worse in cold, dense air.

    I'm thinking I need to swap out the IAJ for the next leaner size, right?

    On the other hand, the bike runs awesome if you are racing around everywhere. Lots of power, no flat spots, tons of fun. Just gotta fix this!
    #1
  2. mousitsas

    mousitsas Long timer

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    Why not 4mm floats as Sportingwood suggests?
    #2
  3. Orangecicle

    Orangecicle On a "Quest"

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    i've had similar issues when I had a vacuum line air leak on one cylinder. The bike would do a little hickup, which sounds like the chain skipping a sprocket tooth, but it is really backfiring into a carb.

    Check your vacuum lines. I check my carb sync with an airflow meter and don't use the vacuum ports, so I sealed all four on my intake manifolds so that I will never have a vacuum leak again.
    #3
  4. avocadofarmer

    avocadofarmer Fruit Coot

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    Hmmm...I'll check those four ports again and the silicon clamps. I've actually got screws placed in mine, seems like that would be pretty air tight.

    Any ideas on the hard starting?
    #4
  5. EastSideSM

    EastSideSM Isn't that dangerous?

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    Simple first, Make sure your carbs are snug into their boots. These engines vibrate and it is easy for the carbs to get unseated. I have had that issue with mine before and thought it was the battery not getting enough to fire it up. My rear carb was slightly unseated and once I got it snugged up, she fired right up.

    How old is the battery? Is it spinning up but cutting out? Or are you getting the "clacking" noise that sounds like a bunch of wrenches are in your cases? IF it is the clacking noise and it has gotten worse, youre starter torque limiter is about to go and you need the upgraded kit.

    Good luck!
    #5
  6. avocadofarmer

    avocadofarmer Fruit Coot

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    Howdy,

    I just rechecked all of the carb vacuum ports. All four are sealed off with bolts in them and a little dab of RTV. The carbs are also fully seated on the boots and all four clamps are tightened to the stops. Everything appears to be snug.

    I took it for another short ride and got 3 backfires. Every time at about 3000 rpm with just a teeny bit of throttle.

    I replaced the clacking starter torque limiter a while ago...so that's no prob. It has a tendency to cough a bit on startup with this jetting and filter setup. Not nearly as bad as that horrific starter torque limiter, however!!

    Thanks for the ideas, fellas...
    #6
  7. D K

    D K Been here awhile

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    Sounds like you are unning lean off idle
    #7
  8. avocadofarmer

    avocadofarmer Fruit Coot

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    Hmmm...I've heard that it's kinda tricky to differentiate lean/rich at low RPM...

    I've messed with it all day, 100% sure that there are no vac leaks anywhere. Still has a hickup.

    It did seem to decrease in frequency when I richened up the Flex jets so maybe that's a sign to richen them up another half turn.
    #8
  9. Katoom72

    Katoom72 Been here awhile

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    Is there a difference in performance on a cold and hot engine?
    #9
  10. avocadofarmer

    avocadofarmer Fruit Coot

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    Nothing that I can tell...I'm usually easy on it until it warms up tho

    The bog off idle is really small and happens only within the first 30 seconds of starting it when cold.
    #10
  11. Katoom72

    Katoom72 Been here awhile

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    I'd think a smaller IAJ would help.

    Stock is 50 so 60 is leaner, you made the carbs breath better with the airbox removal and the problem comes around more on cold dense air. Giving it more fuel on the mixture screws helps aswell.

    So the bigger airjet, easyer breathing/more air intake, cold air all makes it leaner then stock.

    So if u add all of that up the engine is running to lean on idle trough low RPM cruise.

    I'm no carb guru but that's my theory on the issue. If u got no intake leaks and the floats are not way off their stock height then you should try a smaller IAJ.


    Did you balance the carbs yet?
    #11
  12. David37

    David37 Been here awhile

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    Sounds like you have a lean condition caused by your new air filter which is flowing more air than the stock air box. IMO I would increase your pilot jets from 42 to 45. I would also try dropping the clip (raises the needle) on your needle.
    #12
  13. avocadofarmer

    avocadofarmer Fruit Coot

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    I balanced the carbs a few hrs ago...I didn't have to adjust anything...I'll try plugging back in the stock IAJ...IIRC that's the one on the top of the carb...easy to get to. Thanks for the idea.

    David, I'm already on the middle needle setting...(one richer than stock). I'm afraid that another movement would overdo it...?
    #13
  14. max2

    max2 Been here awhile

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    stock air jet and 45 pilots, floats at 4mm, needle 3rd clip, 175/178 mains, air screws 2 frt, 2 1/4 rear
    #14
  15. gefr

    gefr Life is a trip

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    exhaust system? Results? Consumption?

    Cheers.
    #15
  16. avocadofarmer

    avocadofarmer Fruit Coot

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    OK! Thanks to some great advice from the OC I think I've cured the problem! I swapped out the IAJ from 60 to the stock 50's. Put some miles on it and couldn't get it to hickup. Hopefully this will take care of it!

    First tank on this filter I got about 3 mpg better (33 to 36) but that was with a bit of fuel spil from tank removal and a lot of "testing." :evil
    #16
  17. David37

    David37 Been here awhile

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    I still think you should go up to a 45 pilot jet.
    #17
  18. avocadofarmer

    avocadofarmer Fruit Coot

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    I've put about 50 miles on it since swapping out the IAJ to the stock size (50) and it seems to be running great. No hickups, idles nice, tons of power and good economy.

    Maybe this should be added to the jetting matrix!

    :clap
    #18