V4 Carb Sync Guide

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bikemonkey
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V4 Carb Sync Guide

Post by bikemonkey » Sat Feb 09, 2013 7:28 pm

Mods please feel free to sticky if acceptable or delete if necessary.

Disclaimer: I am not responsible for any harm or damage caused to you or your motorcycle or anyone else when you use this guide. Use this guide at your own risk, if you mess your bike up, injure yourself or anyone else it is NOT my fault.



Things you will NEED for the carb balance:

One set of vacuum gauges for a 4 cylinder engine.
Allen key set.
10mm spanner.
8mm spanner.
Long number 2 phillips head screwdriver.
Stubby number 2 phillips head screwdriver.
13mm socket and ratchet.
Pliers, snipe nose or bull nose will do.
Right angle screwdriver OR 7mm socket.
Piece of 2x4 wood to lever carbs up or similar.

Things you may WANT for the carb balance:

Auxiliary fuel tank.
Pair of rubber gloves. (You probably will need these)


I advise that you sync your carbs AFTER you re-jet, adjust float heights, change needle washers and check valve clearances or you may have to do it again.


Firstly remove your tail unit, inspection panels and lowers. (Lowers not necessary but helps with space)
Next remove tank,

Image

airbox,

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carbs,

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and to make things much easier, carb rubbers.

Image

Next you need to remove the blanking screws and the vacuum hose take-off for the fuel tap. The blanking screw for cylinder 4 is accessed next to the thermostat housing here:

Image

Then screw in the adapters from your carb balancing kit and attach the hoses.

Image

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Connect up the hoses to the vacuum gauges making sure you do it so cylinders 1-4 go from left to right on the gauges.

Cylinder config:

Front

2 4


1 3

Rear


After this stick back on your carbs and airbox. Then put back on your tank or connect up your auxiliary fuel tank. (If using your standard tank you'll need to apply a vacuum to the tap if the tap is not modified. If you cannot sustain a vacuum on the tap then apply a vacuum and seal the hose somehow)

Now here comes the tricky, fiddly and potentially painful bit. Depending on how you adjust the carb sync screws.

Start the bike and adjust the idle a little higher than standard, say 1500 rpm - 1700 rpm and let the bike warm slightly. You should see something like this:

Image

If you are using a right angle screwdriver then simply insert the driver into the vee from the left side of the bike and use to turn the adjusters in or out depending on which way you need the level in the gauge to go.

If you don't have a fancy right angle screwdriver or can't get on with it then you'll be using a 7mm socket and a pair of rubber gloves. With the rubber gloves on and socket in hand put your hand into the vee and locate the sync screws with the socket and adjust as appropriate. Be very careful as the longer the engine runs the hotter it will get and could burn your hand even with the gloves on. (Again I take no responsibility for injury, that is your own fault)

Don't press on the screws or it will act like the throttle and increase or decrease the revs and you will get a false reading.

When synchronising the carbs first sync no.4 carb to no.2 carb (master carb). Carb no.4 screw is the only screw at the front of the carbs. Adjust carb no. 4 to match carb no. 2 as close as possible.

Then sync no.1 carb to no.3 carb using the rear screw that is next to carb no.1 (closest screw to you as you enter the vee from the left side of the bike). Again adjust as close as possible to each other.

Finally sync the rear carbs (1 and 3) using the screw that is next to carb no.3 (furthest screw from you as you enter the vee from the left side of the bike). Adjust as close as possible to carbs no. 2 and 4.

Image

(Yes I have done what you think I have there....)

You should now have something that looks like this on your vacuum gauges:

Image

When everything is sync'd then give the throttle a little blip to settle the linkage and re-adjust where necessary. Then turn back your idle speed to the spec and turn off the bike.

After that all you need to do is rip everything apart again, remove the hoses and adapters, re-fit the blanking screws and vacuum take-off and re-assemble the lot!
Last edited by bikemonkey on Sat Feb 09, 2013 8:33 pm, edited 1 time in total.

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Re: Carb Sync Guide

Post by CRM » Sat Feb 09, 2013 8:26 pm

Good Skills chap - stickied
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Re: V4 Carb Sync Guide

Post by Neosophist » Sun Feb 10, 2013 5:16 pm

Looks good, a few pointers

1. There is no need at all to remove airbox or carbs when fitting or removing the balance gauge take-off adapters unless you are doing valve clearances / over hauling the carbs.

Remove the screw and washer from each cylinder with long JIS #2 screwdriver and then screw in the adapter.. the brass ones have a slot cut in them to help this but if its troublesome push the take-off adapter onto a piece of the vaccum hose and use it as a guide to line it upto the hole and screw in. It doesnt need to be super-tight, only enough to compress the o-ring.

On the NC30/35 the take off for cylinder 3 uses the vaccum hose for the tank (the NC2x has a screw on this cylinder also!) so suck on the vacum hose to open the tap, fold the end over to stop the vaccum escaping and use a clothes peg to keep the hose closed.

2. The bike should be warmed upto temperature before starting, and when balacnign the idle set slightly above normal idle.. 14-1500 is fine for the VFR

3. If the fan kicks in becuase you take a long time turn the engine off and wait for it to cool down else the balance will be out.
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Re: V4 Carb Sync Guide

Post by bikemonkey » Sun Feb 10, 2013 6:03 pm

Cheers Neo :peace:

I took all the airbox and that off as I found it easier personally, the cylinder 4 screw was a pain to balance on the end of the screwdriver to get it back in even with the tank etc off.

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Re: V4 Carb Sync Guide

Post by jim157 » Sun Feb 10, 2013 6:36 pm

Top guide, nice one.
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Re: V4 Carb Sync Guide

Post by Sunnyday » Sat Feb 16, 2013 8:45 am

Yes really good of you to share your hard work with us, Can you put up a picture of your makeshift fuel tank as i am doing this job on my bike soon also how do you get round the vacuum side of it as my bike is standard will it pull fuel ok.

Thanks in advance.

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Re: V4 Carb Sync Guide

Post by bikemonkey » Sat Feb 16, 2013 8:54 am

Sunnyday wrote:Yes really good of you to share your hard work with us, Can you put up a picture of your makeshift fuel tank as i am doing this job on my bike soon also how do you get round the vacuum side of it as my bike is standard will it pull fuel ok.

Thanks in advance.
Neosophist wrote:On the NC30/35 the take off for cylinder 3 uses the vaccum hose for the tank (the NC2x has a screw on this cylinder also!) so suck on the vacum hose to open the tap, fold the end over to stop the vaccum escaping and use a clothes peg to keep the hose closed.

I didn't use a makeshift tank, I just used the method above :peace:

If you want to use an auxiliary tank then buy one off eBay or go to your local autostore.

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Re: V4 Carb Sync Guide

Post by johnnie5 » Sat Feb 16, 2013 9:18 am

Sunnyday wrote:Yes really good of you to share your hard work with us, Can you put up a picture of your makeshift fuel tank as i am doing this job on my bike soon also how do you get round the vacuum side of it as my bike is standard will it pull fuel ok.

Thanks in advance.
as below ive used the hold the vacuum on the fuel tap

but i found an old 2 stroke lawnmower so use the fuel tank of it , its great as it has a fuel tap

free and works well on any bike

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Re: V4 Carb Sync Guide

Post by Sunnyday » Sat Feb 16, 2013 5:18 pm

Neosophist wrote:On the NC30/35 the take off for cylinder 3 uses the vaccum hose for the tank (the NC2x has a screw on this cylinder also!) so suck on the vacum hose to open the tap, fold the end over to stop the vaccum escaping and use a clothes peg to keep the hose closed.

I will probs use a plastic petrol can , thanks for info "i will get our lass to suck on it then i shall arrange to bend it over as required".

Good advice.

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Re: V4 Carb Sync Guide

Post by speedy231278 » Thu Feb 21, 2013 12:03 pm

Isn't one difference between the 30 and 35 that the throttle cables are connected to the front left carb on the 30 and rear left on the 35, hence the master carb for the 30 being #2 and the 35 being #1?
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