How to balance your carbs

Where all the workshop knowledge lives together.
User avatar
carmanbikes
Posts: 894
Joined: Sat Dec 22, 2012 11:09 am
Location: Wigan

Re: How to balance your carbs

Post by carmanbikes » Sat Jan 30, 2016 11:58 am

Save This

User avatar
AMCQ46
Posts: 14802
Joined: Mon May 11, 2009 3:54 pm
Location: Worcestershire / Warwickshire border

Re: How to balance your carbs

Post by AMCQ46 » Sun Jan 07, 2018 4:07 pm

put the missing photos back in

A simple "how to" balance the carbs on the VTR. -

as Photobucket has removed all the photos from this post, please use this PDF copy so you can get the words and images together.
pdf link

1st thing you need to do is fit a vacuum adapter to the front cylinder intake. There is one already fitted to the rear which is used to operate the fuel tap, but the front take-off point is blanked off with a 5mm Allen head screw.
You will need to purchase a 5mm threaded brass adaptor if you want to permanently fit the adaptor, or you can use a plastic adapter which probably came with your balance gauge, but if you do this you will have to refit the blanking screw after you do the balancing.

Brass screws from Carbtune http://www.carbtune.co.uk/carbaccs.html, but you get a pack of 4, when you only want 1! perhaps if you call them up they will sell you a single. I suggest you also get a length of vacuum hose from them at the same time.

To fit the screw you have to get the tank off and the airbox, hence it is a lot less hassle to fit the brass one and then you can do any future checks without disturbing the airbox.
If you are going to leave the adapter fitted then they recommend that you remove the o-ring, and use a thread lock sealant. Also donâ€Imaget over tighten, brass is not a strong as steel.

first photo shows the location of the front vacuum take off point.
Image


Then you will need to fit hose to the front cylinder and put a T piece in the rear hose [as as you will need to keep vacuum to the fuel tap to run the engine], the T piece can be bought at Halfords for £1.50, you will find them in the same section as the nuts, bolts and electrical connectors.
Image

As you have the airbox off to fit the adapter, and it is easier to get to the adjuster screw, the first time you balance the carbs it will be easier to do it with the airbox off.

You need to get the petrol tank back on to get the bike started, but you cant fit it in the normal place or you cant reach the adjuster screw. I fit the tank backwards with the hoses on the opposite sides.
Image


At this point you need to fit your balance gauges, these come in many shapes and methods from individual clock gauges, oil manometers or in my case a ball bearing comparator. As it is only 2 cylinders this one is fool proof, it has no calibration errors and is unbreakable :thumbup: the lower ball has the vacuum from each cylinder acting on each side, the upper ball is only for reference showing where zero should be.
Image
Image

Get the engine warm and then lift the idle speed slightly to a point where your gauges are giving a stable reading. if there is any difference between the readings from each cylinder [or in my case if the moving ball is to either side of the reference ball, then you adjust this screw.
Image

which direction will depend on which cyl is high and which is low. your reading will change so you can work out if you are going the correct way or not.
After each adjustment, blip the throttle slightly and let it settle to the fast idle.

Now you have got your carbs balanced the first time, you will not need to take the airbox off next time. The adjuster can be accessed [just] with the airbox in place.
Image
And if you route the 2 open ends of the vac pipes [new one from the front and one from the t-piece in the rear] to a suitable position where you can access them with the tank on you can now periodically check the balance without removing the tank...........clearly if you need to make any adjustment the tank has to come off, but this makes the checking easy.

Image

last job is to blank off the open ends of the 2 vac pipes. I used the plain section of a long M5 Bolt, but I am told Golf tee's are a great alternative...........It is important that you dont have air leaks here so dont try and seal on the treaded section of a screw.

I then tuck these pipes up with the thermstat housing between the V so they cant be seen.

Job done.. go have a cup of tea to congratulate yourself! :beer




Sent from my iPad using Tapatalk
AMcQ

User avatar
sirch345
Site Admin
Posts: 18075
Joined: Mon Aug 25, 2003 9:35 pm
Location: Cornwall, UK

Re: How to balance your carbs

Post by sirch345 » Wed Jan 10, 2018 11:04 pm

Thanks for putting the photo's back Al :thumbup:

Chris.
A closed mouth gathers no foot. :thumbup:

User avatar
Eclectic
Posts: 382
Joined: Sat Mar 26, 2011 12:04 pm
Location: Norwich

Re: How to balance your carbs

Post by Eclectic » Fri Apr 26, 2019 4:43 pm

Having issues with balancing mine. The needles for both are in the "LATE VALVE TIMING OR LEAK AT INTAKE MANIFOLD OR HEAT RISER"

Any ideas what this means to a layman?

Video of her running:
https://www.youtube.com/watch?v=1cc6AVT ... 9mDfsF2HTU

Closer image of the dials:
Image

EDIT:

A better video with some dampening:
https://www.youtube.com/watch?v=4yfPNOr ... e=youtu.be

Ive decided Im overthinking it with the red bars where the needles are pointing and Im just going to balance it

Cheers.
Image

User avatar
sirch345
Site Admin
Posts: 18075
Joined: Mon Aug 25, 2003 9:35 pm
Location: Cornwall, UK

Re: How to balance your carbs

Post by sirch345 » Fri Apr 26, 2019 8:58 pm

Eclectic wrote:
Fri Apr 26, 2019 4:43 pm
EDIT:

A better video with some dampening:
https://www.youtube.com/watch?v=4yfPNOr ... e=youtu.be

Ive decided Im overthinking it with the red bars where the needles are pointing and Im just going to balance it

Cheers.
I agree, if the bike is running fine just get the needles to read the same on the balancer dials :thumbup:

Good to hear from you again :thumbup:

Chris.
A closed mouth gathers no foot. :thumbup:

User avatar
8541Hawk
Posts: 1636
Joined: Sat Jul 21, 2012 4:21 am
Location: Bosque Farms, NM

Re: How to balance your carbs

Post by 8541Hawk » Sat Apr 27, 2019 3:33 am

Eclectic wrote:
Fri Apr 26, 2019 4:43 pm
Having issues with balancing mine. The needles for both are in the "LATE VALVE TIMING OR LEAK AT INTAKE MANIFOLD OR HEAT RISER"

Any ideas what this means to a layman?
They look like standard automotive vacuum\pressure gauges and are labeled as such.
In other words the markings are meant for one gauge check the vacuum pressure on a multi cylinder auto engine.

When hooked to your single 500cc cylinder the reading will be much lower but that is perfectly normal.

Or don't worry what the gauge says, just make them read the same :thumbup:
They call me "Mr. Flat Earther"

User avatar
8541Hawk
Posts: 1636
Joined: Sat Jul 21, 2012 4:21 am
Location: Bosque Farms, NM

Re: How to balance your carbs

Post by 8541Hawk » Sat Apr 27, 2019 3:34 am

Also on balancing the carbs, if you use a swivel right after the 7mm socket you can set the sync with the tank and air box installed with no real issues :thumbup:
They call me "Mr. Flat Earther"

dave.m
Posts: 3
Joined: Sat Apr 27, 2019 5:39 pm

Re: How to balance your carbs

Post by dave.m » Sun Apr 28, 2019 2:15 pm

Hi everyone, I,m a newbie to the site & have only recently purchased a 2002 firestorm. I have just fitted a stage 1 kit & decided to balance the carbs.I understand where the front take off point is but I am unsure about the rear. There is a picture where some one is pointing to the adjusting screw, just behind is a short rubber pipe. Can I detach this pipe at the left end & attach my balance pipe to it ? Will this work ?

dave.m
Posts: 3
Joined: Sat Apr 27, 2019 5:39 pm

Re: How to balance your carbs

Post by dave.m » Sun Apr 28, 2019 2:31 pm

Hi everyone, I,m a newbie to the site & have only recently purchased a 2002 firestorm. I have just fitted a stage 1 kit & decided to balance the carbs.I understand where the front take off point is but I am unsure about the rear. There is a picture where some one is pointing to the adjusting screw, just behind is a short rubber pipe. Can I detach this pipe at the left end & attach my balance pipe to it ? Will this work ?

tony.mon
Posts: 13595
Joined: Wed Jul 25, 2007 9:46 pm
Location: Norf Kent

Re: How to balance your carbs

Post by tony.mon » Sun Apr 28, 2019 4:55 pm

The rear take off point is a mirror image of the front, a cap head screw just below the carb to head rubber.
If there is a pipe already fitted it should be connected to the vacuum operated fuel tap.
Fit a tee piece, and connect a vac guage to it.
It's not falling off, it's an upgrade opportunity.

User avatar
MacV2
Posts: 14451
Joined: Sun Jan 21, 2007 12:07 pm
Location: Grain

Re: How to balance your carbs

Post by MacV2 » Sun Apr 28, 2019 5:55 pm

dave.m wrote:
Sun Apr 28, 2019 2:31 pm
Hi everyone, I,m a newbie to the site & have only recently purchased a 2002 firestorm. I have just fitted a stage 1 kit & decided to balance the carbs.I understand where the front take off point is but I am unsure about the rear. There is a picture where some one is pointing to the adjusting screw, just behind is a short rubber pipe. Can I detach this pipe at the left end & attach my balance pipe to it ? Will this work ?
The picture you refer to is the ajuster on the carbs, this is what you need to adjust to balance the carbs...

The top pic in thats sequence of pics shows the front take off point...

If you look at your bike from the right hand side, into the frame at the back of the front cylinder, thats where the front take off is to be found...

The black knurled knob you can see is the tick over adjuster...

As std the bike will not have a pipe there, thats what you have to fit to do the balance. As std there will be a allen head bolt which you need to remove & fit a brass take off spigot...Fit the pipe to that & thats the front take off sorted...

On the rear you need to be on the left hand side of the bike & now your looking at the front of the rear cylinder, this should already have a vac tube fitted as thats what runs to the petcock, this is what you need to cut & put a T-peice into with an extra lenght of tube on...

Then your balancer tubes fit into the extra pipe from the T & onto the tube from the front take off...

The adjuster with the finger pointing at it in the pic is what you adjust to get the carbs balanced... Top tip spray that with a good shot of WD-40, GT85 or whatever as it has a tendancey to seize up...

Once you have done the balance you must plug the end of the hoses you have fitted...Golf tees work well...
Lowering the tone since 2007...

dave.m
Posts: 3
Joined: Sat Apr 27, 2019 5:39 pm

Re: How to balance your carbs

Post by dave.m » Sun Apr 28, 2019 7:07 pm

Thanks for the replies. When I remove the fuel pipe from the petrol tank fuel escapes it does not have a vacuum pipe, so do I have a part missing ?

User avatar
Commando77
Posts: 104
Joined: Sun Oct 08, 2017 9:35 pm
Location: Fleet, Hampshire

Re: How to balance your carbs

Post by Commando77 » Sun May 05, 2019 5:36 pm

I guess you've a large tank which had the vacuum device bolted to the rear tank brkt. The tank pipe is open all the time but I guess you found that by now :D

Post Reply