03, ZR-900 CARB, NEEDLE ADJUSTMENT?? - HCS Snowmobile Forums

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Old 01-03-2010, 11:17 AM   #1 (permalink)
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Could someone please explain, I have a 900 with 3 minnor bolt on mods, V-Force Reeds, Y-Pipe, Clutched, & CAN, all D&D products, It has been "Jetted" down one size, My plug color after a hard run are a DRY slightly darker brown, at approx 20deg, when it dips down into single digits in temp I always add a splash of oil to my full tank of gas, just to be safe, My Question is this, My e-clips are exactly in the middle of the "Needles" in "WHAT DIRECTION" do in move the e-clips to richen it up, so I can STOP adding oil to my gas in extreme temp, I don't want to have to put back in the stock Jets because they are to black, I don't want to sacrifice all my performance...ALSO...In the "NEEDLE" Adjustment for TOP END, Oil enjection? Thanks Guys...zrpower
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Old 01-03-2010, 12:34 PM   #2 (permalink)
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Running the middle position on a ZR9 is playing with a midrange burndown-especially with temps below 20 degrees. To richen it you must lower the clip one notch which raises the needle allowing more fuel. Stock mains are 430's so you're running 420's? I wouldn't go any leaner with todays' gas. And I don't believe in adding additional oil to the gas unless it gets extremely cold. Adding oil actually makes your fuel/air mixture leaner as it thickens the fuel and makes it slightly harder to draw thru the jets.
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Old 01-03-2010, 03:00 PM   #3 (permalink)
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Quote:
Running the middle position on a ZR9 is playing with a midrange burndown-especially with temps below 20 degrees. To richen it you must lower the clip one notch which raises the needle allowing more fuel. Stock mains are 430's so you're running 420's? I wouldn't go any leaner with todays' gas. And I don't believe in adding additional oil to the gas unless it gets extremely cold. Adding oil actually makes your fuel/air mixture leaner as it thickens the fuel and makes it slightly harder to draw thru the jets.[/b]
Thank you very much jefro, that was some awesome info that even "I" understand!!lol Your exactly right on my jetss, there 420s!! I will seriously take your advice and NOT add oil to gas anymore!! But in my current situation your "Recommending" that I LOWER the clip ONE NOTCH, this will darken up the Plugs right? Thanks Again bro! John
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Old 01-03-2010, 08:59 PM   #4 (permalink)
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Yeah, I'd say put 'em back to the stock position(#4) which is the fourth from the top(or second from the bottom) and give it a try. Some 900's, mine included, run a little fat off the bottom at the stock setting and needed to be leaned out slightly to position 3 1/2 or so with a needle shim kit: http://www.exhaustgas.com/ProductDetail.as...D=*&RepID=
This should darken your plugs a little at part throttle settings only. Always check your plugs after changing needle settings. It's also common on the ZR9's to stagger the jetting(run one size richer on the MAG side) as the MAG side runs slightly hotter thaqn the PTO side. I also run 1/4 notch richer on the needle on the MAG side to even out the midrange temps on my Digitron. Also, do not cruise at a steady throttle setting for a long time as the EGT's will slowly climb to uncomfortable levels if your needles aren't rich enough. Varying the throttle will keep the temps down. One more thing, the 900's don't gain very much by jetting them on the edge. Very little power is lost by jetting safe for U.P. fuel.
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