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Old 02-02-2008, 10:23 PM   #1 (permalink)
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1993 Mxz 470 won't idle

Fresh gas and plugs was the first thing done to fix an idle issue. I have dismantled, cleaned, and checked the settings on the carbs of this 1993 MXZ 470. The air mixture is set back 1.5 turns from seated as per specs. The fuel filter has been replaced. It runs smooth over 2500rpm but below this is eventually stalls unless you bring the rpms back up. The spec idle is 1500-1700rpm.
Is this an indication of a fuel pump problem??

Last edited by Pete C.; 02-02-2008 at 10:25 PM. Reason: Better title
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Old 02-03-2008, 05:09 AM   #2 (permalink)
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No, likely the idle circuit is still partially clogged.
Clean the carbs by using the soak method and chase the jet with a piece of wire or mono-filament fish line to ensure that they are clear and blow them out with compressed air.
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Old 02-05-2008, 04:26 PM   #3 (permalink)
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I have the same problem.. i got a 93 formula plus and it runs great when your moving but it idles real low and will stall after about 40 secconds if you don't keep it going.. it will fire right back up after it stalls.... so clean the carbs?i have never cleaned them before but i have never had the need to it always ran great up till last year thats when it started to idle low.

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Old 02-05-2008, 05:11 PM   #4 (permalink)
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buddies sled did this and it was a cracked and leaking carb boot
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Old 02-05-2008, 06:44 PM   #5 (permalink)
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carb boots are fine... no leaks they look brand new.. i think i just gotta clean em and just set the idle.
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Old 02-05-2008, 08:55 PM   #6 (permalink)
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All, I found the problem and the sled now idles without stalling. Here's how! Inside the VM34 Mikuni carbs is the pilot jet (supplies gas at idle), needle/ needle jet (supplies gas at midrange), and main jets (full throttle). The pilot jet is easily unscrewed with a flathead screwdriver. It has an opening as small as a needle with 6 additional openings on its body. Remove the float bowl and inside one of the crevices is the brass pilot jet. I simply used a needle to poke all the holes and used compressed air to blow all the junk out. After this you may as well clean your main jets as well. Unscrew the top of the carb to pull out the slide and blow out the needle jet as well. Finally, I used a small punch to remove the pin that holds some other small jet?? Be careful removing the retainer ring, and pull out the spring loaded mechanism to reveal another orifice.
Reassemble and set the air mixture as per spec, in my case it was 1.5 turns back from seated. I also used a marker on the idle screws which I backed out 2 full truns from seated. The sled fired immediately, and idled at 1600rpm with no further problems. Hope this helps. Pete
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