2003 ZR900 Idle adjustment - Page 2

mod zr 700 · 12-10-2007, 01:59 PM

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

tommcat · 12-10-2007, 03:13 PM

Quote:

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

mod zr 700 · 12-10-2007, 06:38 PM

Quote:

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..

bigblock900 · 12-10-2007, 08:23 PM

Quote:

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.

tommcat · 12-11-2007, 07:36 AM

Quote:

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

Scott S · 12-11-2007, 09:10 AM

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.

trdehmer · 12-17-2007, 09:36 AM

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?

zr sled head · 12-17-2007, 10:01 AM

Most common to backfire on start up if the RPM is high when shut off...............what is your base / hot idle speed?

trdehmer · 12-17-2007, 01:46 PM

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.

zr sled head · 12-17-2007, 02:56 PM

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.

12-10-2007, 01:59 PM	#11 (permalink)
mod zr 700 Super Advanced Member Join Date: Oct 2006 Posts: 1,847 Location: south harbour, cabot trail	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 __________________ zr 700

12-11-2007, 09:10 AM	#16 (permalink)
Scott S Super Advanced Member Join Date: Sep 2003 Posts: 1,890 Current Sled(s): 2003 Arctic Cat ZR9, 2012 F1100 SnoPro Location: SWO Favorite Riding Area: Ontario - anywhere it snows! Age: 48 Riding Since: 1975	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. __________________ Lead by example, it all begins with you! Have a great day! Scott

12-17-2007, 09:36 AM	#17 (permalink)
trdehmer Super Advanced Member Join Date: Mar 2003 Posts: 3,133 Current Sled(s): 2012 F1100T Retro & 2003 F7 Location: Minnesota Riding Since: 1984	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? __________________ Previous Sleds: 2010 Z1 Turbo LXR 2002.5 ZR900 1999 XC 700 SP 1994 XLT SP 1990 Polaris 500 1990 Polaris 340 Sport 1984 Polaris 480 Trail A Phazer 1969 Massey Ferg Ski Whiz

12-17-2007, 01:46 PM	#19 (permalink)
trdehmer Super Advanced Member Join Date: Mar 2003 Posts: 3,133 Current Sled(s): 2012 F1100T Retro & 2003 F7 Location: Minnesota Riding Since: 1984	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. __________________ Previous Sleds: 2010 Z1 Turbo LXR 2002.5 ZR900 1999 XC 700 SP 1994 XLT SP 1990 Polaris 500 1990 Polaris 340 Sport 1984 Polaris 480 Trail A Phazer 1969 Massey Ferg Ski Whiz

12-17-2007, 10:01 AM	#18 (permalink)
zr sled head Super Advanced Member Join Date: Dec 2002 Posts: 9,842 Current Sled(s): '11 800 Ltd / '07 F6 sp Previous Sled(s): '08 F1000 sp / '07 F1000 sp / '02 ZR800-900 Location: Toronto Favorite Riding Area: A snow covered one. 10-11 Mileage: 4000ish Age: 99 Riding Since: 1861	Most common to backfire on start up if the RPM is high when shut off...............what is your base / hot idle speed?

12-17-2007, 02:56 PM	#20 (permalink)
zr sled head Super Advanced Member Join Date: Dec 2002 Posts: 9,842 Current Sled(s): '11 800 Ltd / '07 F6 sp Previous Sled(s): '08 F1000 sp / '07 F1000 sp / '02 ZR800-900 Location: Toronto Favorite Riding Area: A snow covered one. 10-11 Mileage: 4000ish Age: 99 Riding Since: 1861	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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