GStwin.com GS500 Message Forum

Main Area => General GS500 Discussion => Topic started by: stoo on July 13, 2003, 03:31:31 AM

Title: Mixture Screw
Post by: stoo on July 13, 2003, 03:31:31 AM
Just done an overall on the carbs (the missus still ain't talking to me :x  did it on the kitchen table, spilt petrol all over it, now it's got a couple of nice stains on it). Any way i'm a little confused. my manual says turn out the mixture screw 1.1/4 turns (it's a 1991 bike) but when i dissassembled the carbs they were set at 2 turns?? and i've read on this site about turning it 3 or 3.1/2 turns. What does this screw actually do and what is the best setting?? :oops:  its fitted with standard 40 pilots & 120 mains.
Also, is balancing carbs really necessary as i dont want to fork out precious cash on something i'm only going to use once in a blue moon. :P
Title: Re: Mixture Screw
Post by: XealotX on May 09, 2010, 08:25:09 PM
Beats me. I would guess that balancing the carbs would be important.

I don't really have an answer to this question. I just wanted to get to 400 posts this evening and felt bad that nobody had answered this question in nearly 7 years.
Title: Re: Mixture Screw
Post by: romulux on May 09, 2010, 08:35:37 PM
You can make your own sync tool for a few bucks:

http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=build+carb+sync+tool (http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=build+carb+sync+tool)

The mix screw adjusts the amount of air allowed to draw fuel through the low speed circuit.

When you turn it in, you occlude a passageway that lets air through, so less air gets through and less fuel gets drawn with the air.

When you turn it out, you open up the passageway and more fuel comes through with the air.

In other words, turning it out enrichens the mixture, turning it in leans the mixture.

From the factory, it's set around 2 turns out.  What manual do you have, btw?
Title: Re: Mixture Screw
Post by: bombjack on May 09, 2010, 10:32:56 PM
Buy a Carbtune pro. It's cheaper than having your shop balance your carbs and you can sell the tool after using it to make it even cheaper.
Title: Re: Mixture Screw
Post by: 007brendan on May 09, 2010, 11:10:17 PM
You can do a pretty good job syncing the carbs by eye.  Or you can create your own carb sync tool for about ~$12 using colored water and aquarium accessories.  Here's mine:

(http://lh3.ggpht.com/_0Z0uVtnoOo8/S-eioMHbqqI/AAAAAAAAAMM/28EEJ7m_o9M/s512/DSC_0702.JPG)
Title: Re: Mixture Screw
Post by: Porkchop on May 10, 2010, 12:25:18 PM
I guess stoo felt ignored and left.  He hasn't been seen since August of 2003.

- Porkchop
Title: Re: Mixture Screw
Post by: sledge on May 10, 2010, 01:29:23 PM
Quote from: XealotX on May 09, 2010, 08:25:09 PM
I don't really have an answer to this question. I just wanted to get to 400 posts this evening and felt bad that nobody had answered this question in nearly 7 years.

:D :D :D :D
Title: Re: Mixture Screw
Post by: PachmanP on May 10, 2010, 06:17:10 PM
Quote from: XealotX on May 09, 2010, 08:25:09 PM
Beats me. I would guess that balancing the carbs would be important.

I don't really have an answer to this question. I just wanted to get to 400 posts this evening and felt bad that nobody had answered this question in nearly 7 years.

:nono: :nono: :nono: :cheers: :icon_razz:

Also having done/tried a carb synch this weekend I disagree. It's a pain in the rump on an 04, and I probably did more to mess up the carbs in the process than I did to correct anything...
Title: Re: Mixture Screw
Post by: gregvhen on May 10, 2010, 08:43:37 PM
Quote from: 007brendan on May 09, 2010, 11:10:17 PM
You can do a pretty good job syncing the carbs by eye.  Or you can create your own carb sync tool for about ~$12 using colored water and aquarium accessories.  Here's mine:

(http://lh3.ggpht.com/_0Z0uVtnoOo8/S-eioMHbqqI/AAAAAAAAAMM/28EEJ7m_o9M/s512/DSC_0702.JPG)


or use gas instead of water so if it gets sucked into the engine it just burns
Title: Re: Mixture Screw
Post by: gregvhen on May 10, 2010, 08:45:41 PM
oh, and the mixture screw lets more or less gas into the mixture. theres a port that the gas takes that goes past the inside tip of the mixture screw on the inside of the carb, screwing the screw out makes the path bigger, thus allowing more gas to flow and enriching your mixture and visa versa
Title: Re: Mixture Screw
Post by: scratch on May 11, 2010, 07:59:46 AM
Quote from: gregvhen on May 10, 2010, 08:43:37 PM
or use gas instead of water so if it gets sucked into the engine it just burns
Great idea!

Synchronizing the vacuum between the carbs ensures that one cylinder will not be working harder than the other one, which would lead to premature wear, inconsistant carburetion, hesitant acceleration, overheating, decrease in power...