2003 ZR900 Idle adjustment - Page 2 - HCS Snowmobile Forums

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Old 12-10-2007, 02:59 PM   #11 (permalink)
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i got a zr 700 that i just currently put a set of ported cylinders/ shaved heads, twin psi race pipes and a set of 46.5mm carbs..when i finally got her together and fired last night up it seemed to be running a little bit in one cylinder at idle but when giving her a god bit of throttle when she was tied up in the garage it seemed to be fine...let her idle back down and it seemed to be back on one cylinder again until i gave it a few shots of throttle to get her engauging again than it was fine...did this 4-5 times and it did it every time...one cylinder at idle than get the track moving a little and revs up to around 4-5-6000rpm's and it was working fine as kind....and it is only one cylinder doing this, one plug is dry and the other is soaked?...what should my air screws be set at?.any thoughts on this would be great...and it was idling at around 25-2600rpm's with my idle screws out as far as they could go
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Old 12-10-2007, 04:13 PM   #12 (permalink)
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i got a zr 700 that i just currently put a set of ported cylinders/ shaved heads, twin psi race pipes and a set of 46.5mm carbs..when i finally got her together and fired last night up it seemed to be running a little bit in one cylinder at idle but when giving her a god bit of throttle when she was tied up in the garage it seemed to be fine...let her idle back down and it seemed to be back on one cylinder again until i gave it a few shots of throttle to get her engauging again than it was fine...did this 4-5 times and it did it every time...one cylinder at idle than get the track moving a little and revs up to around 4-5-6000rpm's and it was working fine as kind....and it is only one cylinder doing this, one plug is dry and the other is soaked?...what should my air screws be set at?.any thoughts on this would be great...and it was idling at around 25-2600rpm's with my idle screws out as far as they could go[/b]
Normally i say to go with the factory specs to start with and adjust from there but with a carb that large i wouldnt be able to guess. seems like an awful lot of carb for a 700
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Old 12-10-2007, 07:38 PM   #13 (permalink)
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Normally i say to go with the factory specs to start with and adjust from there but with a carb that large i wouldnt be able to guess. seems like an awful lot of carb for a 700[/b]
i was kindive thinking that as well....but with the twin race pipes, porting and the large carbs i thought there would be enough flow to pull the larger carbs....the carbs have the power jetts installed onto them as well...i might try a few other thing to see if i can get her tuned in and if not i might have to go back to the 40mm carbs to see if it is a LARGE carb problem...thanks..
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Old 12-10-2007, 09:23 PM   #14 (permalink)
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i was kindive thinking that as well....but with the twin race pipes, porting and the large carbs i thought there would be enough flow to pull the larger carbs....the carbs have the power jetts installed onto them as well...i might try a few other thing to see if i can get her tuned in and if not i might have to go back to the 40mm carbs to see if it is a LARGE carb problem...thanks..[/b]
Trail ported 900's with twin pipes run stock 40mm carbs, and run good. I can't see your 700 even ported requiring that large of a carb,IMO.
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Old 12-11-2007, 08:36 AM   #15 (permalink)
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i was kindive thinking that as well....but with the twin race pipes, porting and the large carbs i thought there would be enough flow to pull the larger carbs....the carbs have the power jetts installed onto them as well...i might try a few other thing to see if i can get her tuned in and if not i might have to go back to the 40mm carbs to see if it is a LARGE carb problem...thanks..[/b]
well for a comparison i'm making 180 horses with a modded 900 and going through the stock TM40s
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Old 12-11-2007, 10:10 AM   #16 (permalink)
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I'd verify the carbs settings. If they are off I'd go stock setup to start.

Stock 03, 900
Air Screw - 2 turns out
Fuel - 1 1/2 turns out

The air screw can be tweaked back to 1 3/4 out to help a bit with the idle hang. The air screw is very sensitive so try a bit at a time. It is the small screw.
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Old 12-17-2007, 10:36 AM   #17 (permalink)
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Turning the air screw in seemed to help with the idle. However, it still backfired on a ride yesterday. Same situation for the most part, trail rode at normal speeds and came to a stop and shut it down. Started it back up and it backfired.

Is this a sign its running to rich?
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Old 12-17-2007, 11:01 AM   #18 (permalink)
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Most common to backfire on start up if the RPM is high when shut off...............what is your base / hot idle speed?
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Old 12-17-2007, 02:46 PM   #19 (permalink)
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After the sled is warmed up good and riding it, it will idle at about 1500 RPM (but it takes a short time to drop to it, might be at 3000 for a short period of time then will drop back to 1500). Right when I start it first thing for the day it will be at 1500 or so and stay there.
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Old 12-17-2007, 03:56 PM   #20 (permalink)
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I'd turn the air screw back out and reset the idle speed to about where it is now...............Oh, shelf in or out? Shelf out makes em way more prone to hanging.
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