2003 zr 900 mods done carb help needed - HCS Snowmobile Forums

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Old 11-22-2011, 09:19 PM   #1 (permalink)
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Default 2003 zr 900 mods done carb help needed

My sled has d&d twin 1010 pipes as well as the d&d clutch kit. All I have done was increase the main jets to 560 mains and adjust the air screws. Here is where my question comes in. I want to put a power breather on my sled but do not understand that much about low speed carb tuning. I know how to check full throttle by flipping the choke open while holding it wide open and seeing if it bogs down or picks up. How do i do low and mid range tuning? strictly by reading piston wash? I was told to raise the needle one clip position and adjust the fuel screws from there. Can anyone shed some light on this for me. I have spent the last two days trying to find a good tuning article or similar setups. I also have the typical rising idle that eventually falls with these sleds, many people say to just leave it alone. If anyone has a good writeup on the mikuni flat slide carbs for these sleds it would be greatly appreciated. thanks
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Old 11-22-2011, 10:23 PM   #2 (permalink)
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I dont know if Id raise the clip as it leans the mid, Im pretty sure I remember some Guys using F7 needles that have a different taper. Perhaps a call to D&D would shed some light on a good baseline, dont expect to pass a gas station with those mains.
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Old 11-22-2011, 10:37 PM   #3 (permalink)
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I dont know if Id raise the clip as it leans the mid, Im pretty sure I remember some Guys using F7 needles that have a different taper. Perhaps a call to D&D would shed some light on a good baseline, dont expect to pass a gas station with those mains.
One of their techs told me to raise the clip on the needle and adjust from there. Actually my gas mileage is about the same with those mains as with the sled the way it was stock. I am going to try and call them tomorrow to get to the bottom of this.
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Old 11-22-2011, 11:07 PM   #4 (permalink)
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you sure that they didn't say to "raise the needle a clip"? (richer). it's easy enough to try it either way. IMO, 560s are plenty rich and like you believe they said, you may need to lower the needle (leaning it) to get it to be crisp enough off the start, just know that this is going to lean your midrange/cruising rpm and you will need to be aware in that area.
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Old 11-23-2011, 12:04 AM   #5 (permalink)
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you sure that they didn't say to "raise the needle a clip"? (richer). it's easy enough to try it either way. IMO, 560s are plenty rich and like you believe they said, you may need to lower the needle (leaning it) to get it to be crisp enough off the start, just know that this is going to lean your midrange/cruising rpm and you will need to be aware in that area.
Right, thats what how I was implying it. I should have clarified that. My thinking is that if I add the powerbreather I will have to add more fuel down low and in the midrange to compensate for the extra air. This is why I am trying to figure out how to understand how to go about adding air or fuel or taking it away as its needed.
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