carbs - how the frak do they work?

Worldtraveller · September 25th, 2014, 12:58 PM

So not my Ninjette, she's running fine.

My wife's bike, however....

It's an '07 GS500F. It hasn't been ridden in over 3 years now, and I had pulled the carbs, removed and cleaned the jets, and put it back together (I hope correctly).

I can get it to start ok with the choke on. It won't idle though, without choke, and adjusting the idle doesn't seem to make a difference. Any ideas where I should start with the troubleshooting? There's a chance I didn't get all of the various interconnecting tubes in the right place, but I think I did. Should I borrow a carb sync tool and see if I can get that done first (although wouldn't it have to at least idle and stay running to do that)?

I'm open to suggestions. Thanks.

adouglas · September 25th, 2014, 01:02 PM

Googling "gs500 carburetor" yielded considerable video and troubleshooting content.

flitecontrol · September 25th, 2014, 01:25 PM

When gas is left in a carb, it can obstruct the internal passages as well as the jets. Carb spray isn't a sufficiently aggressive cleaner to remove stubborn deposits. Sounds like your carbs are still dirty. Get a can of Berrymans Chem Dip (around $16 at the local Wal Mart) and soak only the metal parts for a minimum of 24-48 hours. Rinse well with water and blow out all the openings with high pressure compressed air. Or if you have access to a sonic cleaner, use that as it will clean it quickly.

The Chem Dip can be used several times before it becomes contaminated and needs to be replaced.

Draining the carb before extended storage will keep the carbs from gumming up.

Rifleman · September 26th, 2014, 09:55 PM

Carbs = magic...

However, you can learn magic.

Yes as Flitecontrol said, gas, old gas... old gas that evaporates in a carb leaves lacquer or varnish... in very small passages and ports...

two things that work, soaking in carb cleaner and blowing it out with high pressure air. may take two or three times...

once you get them clean, they should work much better... having to keep the bike choked to keep it running at idle... = lacquer in the idle jets (the smallest)

verboten1 · September 26th, 2014, 10:00 PM

I bought an ultrasonic cleaner specifically for carb work. If a carb comes off a bike, it now comes apart and takes a nice 20 minute long heated bath and it's worked on everything I have put in there!

Worldtraveller · September 30th, 2014, 08:40 AM

So not just the jets, huh? I've looked at a couple of the various S500 videos, but not all of them yet. I'd love to just trailer it over to a professional, but I'm trying to learn how to do this stuff on my own to save money, and support my racing habit.....

HKr1 · October 2nd, 2014, 01:29 PM

Racer x · October 2nd, 2014, 01:30 PM

Replace the pilot jets.

FrugalNinja250 · October 2nd, 2014, 03:15 PM

At the most basic level, carbs work using the Bournulli principle: http://en.wikipedia.org/wiki/Bernoulli%27s_principle

Essentially, the pressure of air in any given spot is related to its velocity. Carbs have a section with reduced area such as a venturi, and in that spot the air speed has to increase. It increases because the same amount of air is going through a smaller area. Because the speed increases the pressure decreases, and that draws fuel out of the float bowl through metered orifices called jets.

But really, you still have solidified crap inside the orifices, passages, and jets in the carb. Carb spray or brake cleaner (my preferred fluid) should spray through all openings and passages. Removing all the jets, pilot tubes, needles, etc, is generally required when cleaning carbs that sat for a very long time. Also, remove the rubber bits like the diaphragms, O-rings, and gaskets before cleaning as most cleaning fluids will damage these "soft" parts.

Rifleman · October 3rd, 2014, 07:20 AM

wow, that is a beautiful diagram of a CV carb.

you see the "pilot jet" (item #1) that is going to be your "it won't idle" problem area... that path, through the jet, to the up stream or down stream side of the butterfly, as well as the "idle mix screw"...

all those path ways are VERY small, literally the size of a sewing needle. Maybe even smaller... very prone to varnish clogging... they have no moving parts and only the smallest delta P when operating so nothing to really clean them during normal ops...

the main jet will always be in the "middle" right under the main venturi... the pilot will be another brass screw in type jet... but it will be off center somewhere under the float.

that's where you want to spray the carb cleaner, and blow it out with compressed air until you can feel air blowing around the butterfly... back the idle mix screw out all the way and clean... you can try and shut it (count the turns going in) and then put the same amount of turns coming back out when you assemble after cleaning... 2.5 turns is a common number... although some are 4 turns open...

be sure to clean your choke ports as well... the worst thing for a carb is to sit full of gas, and then dry out...

everything gets clogged and coated.

September 25th, 2014, 01:02 PM	#2
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Googling "gs500 carburetor" yielded considerable video and troubleshooting content. __________________________________________________ I am NOT an adrenaline junkie, I'm a skill junkie. - csmith12 Nam et ipsa scientia potestas est. Heri historia. Cras mysterium. Hodie donum est. Carpe diem.

September 26th, 2014, 10:00 PM	#5
verboten1 ninjette.org certified postwhore Name: Jason Location: Monroe, MI Join Date: May 2013 Motorcycle(s): '75 CB550:.'82 XV920:.'00 KLR650:.'00 EX250:.'08 Ninja 250 Posts: A lot. MOTM - June '15	I bought an ultrasonic cleaner specifically for carb work. If a carb comes off a bike, it now comes apart and takes a nice 20 minute long heated bath and it's worked on everything I have put in there! __________________________________________________ '82 XV920: Soon to be tracker--'00 KLR685:adv --'04 DRZ400E--'12 Super Tenere --'13 Versys Ride more, worry less.

October 2nd, 2014, 01:30 PM	#8
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	Replace the pilot jets. __________________________________________________ Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
08 carbs on 07	sigma44	1986 - 2007 Ninja 250R Tech Talk	10	January 26th, 2015 10:05 AM
Need 08+ Carbs	Donnyd21	Items Wanted	2	September 19th, 2014 04:38 PM
[motorcycle.com] - AMA Says To Ride To Work On Ride To Work Day	Ninjette Newsbot	Motorcycling News	0	June 9th, 2014 11:50 AM
DIY- Carb Work on 2008 Ninja 250 carbs	kkim	2008 - 2012 Ninja 250R Tech Talk	40	September 8th, 2011 07:51 AM
Shim Carbs - Would These Work?	nattygirl	2008 - 2012 Ninja 250R Tech Talk	13	February 16th, 2011 12:30 PM

September 25th, 2014, 12:58 PM	#1
Worldtraveller ninjette.org sage Name: Lane Location: Medford, OR Join Date: May 2014 Motorcycle(s): Ninja 250 (trackbike), CBR600RR, GS500F Posts: 588	carbs - how the frak do they work? So not my Ninjette, she's running fine. My wife's bike, however.... It's an '07 GS500F. It hasn't been ridden in over 3 years now, and I had pulled the carbs, removed and cleaned the jets, and put it back together (I hope correctly). I can get it to start ok with the choke on. It won't idle though, without choke, and adjusting the idle doesn't seem to make a difference. Any ideas where I should start with the troubleshooting? There's a chance I didn't get all of the various interconnecting tubes in the right place, but I think I did. Should I borrow a carb sync tool and see if I can get that done first (although wouldn't it have to at least idle and stay running to do that)? I'm open to suggestions. Thanks.

September 25th, 2014, 01:25 PM	#3
flitecontrol ninjette.org guru Name: Lee Location: Monroe, LA Join Date: Feb 2014 Motorcycle(s): Rebel 250s, Ninja 250s VN750s (currently nine total) Posts: 465	When gas is left in a carb, it can obstruct the internal passages as well as the jets. Carb spray isn't a sufficiently aggressive cleaner to remove stubborn deposits. Sounds like your carbs are still dirty. Get a can of Berrymans Chem Dip (around $16 at the local Wal Mart) and soak only the metal parts for a minimum of 24-48 hours. Rinse well with water and blow out all the openings with high pressure compressed air. Or if you have access to a sonic cleaner, use that as it will clean it quickly. The Chem Dip can be used several times before it becomes contaminated and needs to be replaced. Draining the carb before extended storage will keep the carbs from gumming up.

September 26th, 2014, 09:55 PM	#4
Rifleman Old and slow Name: Lohman Location: Aiken, S.C. Join Date: May 2014 Motorcycle(s): Suzuki TL1000R, Honda CBR600F3, Ninja 250 Posts: 889	Carbs = magic... However, you can learn magic. Yes as Flitecontrol said, gas, old gas... old gas that evaporates in a carb leaves lacquer or varnish... in very small passages and ports... two things that work, soaking in carb cleaner and blowing it out with high pressure air. may take two or three times... once you get them clean, they should work much better... having to keep the bike choked to keep it running at idle... = lacquer in the idle jets (the smallest)

September 30th, 2014, 08:40 AM	#6
Worldtraveller ninjette.org sage Name: Lane Location: Medford, OR Join Date: May 2014 Motorcycle(s): Ninja 250 (trackbike), CBR600RR, GS500F Posts: 588	So not just the jets, huh? I've looked at a couple of the various S500 videos, but not all of them yet. I'd love to just trailer it over to a professional, but I'm trying to learn how to do this stuff on my own to save money, and support my racing habit.....

October 2nd, 2014, 03:15 PM	#9
FrugalNinja250 ninjette.org certified postwhore Name: Frugal Location: Dallas/Fort Worth (DFW) Join Date: Mar 2010 Motorcycle(s): Several Posts: A lot.	At the most basic level, carbs work using the Bournulli principle: http://en.wikipedia.org/wiki/Bernoulli%27s_principle Essentially, the pressure of air in any given spot is related to its velocity. Carbs have a section with reduced area such as a venturi, and in that spot the air speed has to increase. It increases because the same amount of air is going through a smaller area. Because the speed increases the pressure decreases, and that draws fuel out of the float bowl through metered orifices called jets. But really, you still have solidified crap inside the orifices, passages, and jets in the carb. Carb spray or brake cleaner (my preferred fluid) should spray through all openings and passages. Removing all the jets, pilot tubes, needles, etc, is generally required when cleaning carbs that sat for a very long time. Also, remove the rubber bits like the diaphragms, O-rings, and gaskets before cleaning as most cleaning fluids will damage these "soft" parts.

October 3rd, 2014, 07:20 AM	#10
Rifleman Old and slow Name: Lohman Location: Aiken, S.C. Join Date: May 2014 Motorcycle(s): Suzuki TL1000R, Honda CBR600F3, Ninja 250 Posts: 889	wow, that is a beautiful diagram of a CV carb. you see the "pilot jet" (item #1) that is going to be your "it won't idle" problem area... that path, through the jet, to the up stream or down stream side of the butterfly, as well as the "idle mix screw"... all those path ways are VERY small, literally the size of a sewing needle. Maybe even smaller... very prone to varnish clogging... they have no moving parts and only the smallest delta P when operating so nothing to really clean them during normal ops... the main jet will always be in the "middle" right under the main venturi... the pilot will be another brass screw in type jet... but it will be off center somewhere under the float. that's where you want to spray the carb cleaner, and blow it out with compressed air until you can feel air blowing around the butterfly... back the idle mix screw out all the way and clean... you can try and shut it (count the turns going in) and then put the same amount of turns coming back out when you assemble after cleaning... 2.5 turns is a common number... although some are 4 turns open... be sure to clean your choke ports as well... the worst thing for a carb is to sit full of gas, and then dry out... everything gets clogged and coated.