Join Date: Jun 2007
I Ride: 1985 gsxr 1999 bandit 1200 zx6r
CARB BALANCING/SYNCHRONISING :----
When synchronising your carbs, what you're trying to do is synchronise the throttle plates of the 4 of the carbs.
Each cylinder ideally should be carrying 25% of the load. Carbs not synchronised properley will affect the quality of the idle and will run poorly.
It is a good idea to check the "valve" clearence before checking the carb synchronisation, as it can affect the synch adjustment.
Remove the air filter box- or pods depending whet setup you have fitted! Looking from the back of the carbs in between each carb is a small screw - 3 in total ( I will post pics when the camera is working again.) 1 screw will sync #1 and 2 another will sync #3 and 4 and the middle will sync them all together.
On the carbs (where joining to the head) there is a small rubber cap! ( Again sorry for lack of pics) that is where you will be connecting your manometer - or carb sync tool. The most common type are mercury tube types - they're inexpensive an will get the job done a treat. Another type consists of dial gauges in a rack. Make sure you dont loose those caps you have removed - you will need to put them back on!!
If it is possible, it is a good idea to have a fan in front of the engine to simulate the cold air to cool the engine. ( If this is your first carb sync - it could take a while to get right - and the engine is gonna get hot) while you're digging around finding you a phillips head screwdriver - you'll need that to make the adjustments!
Assuming you haven't already - remove the petrol tank, at this point you will need to figure out how you're gonna deliver the fuel to the engine while it is off, you can either:
a) Get yer mate to hold the tank while you sync.... in which case dont remove the pipes.
b) Grab a plastic bottle and fabricate it to take a pipe and a "T" section to join 2 pipes like the ones you just removed from the tank... You can buy special tools to do the job depending on wether you got the cash to chuck at it!
Right - lets get started!
Connect 1 hose from the manometer to each of those 4 fittings where you have removed the rubber caps from, keep an eye on which fitting is on which carb or youll get all messed when adjusting also be sure to block off the vaccum line to the gastap. A vaccum leak like that will cause you problems.
Now fire it up! Let the engine run till it warms up and set the idle screw to approximately 1700rpm looking at the rev limiter...turn clockwise to increase the idle.
If you're using the mercury type manometer, be careful with the throttle, if you rev the motor and let the throttle slam shut you can wind up sucking all the mercury out the gauge and into the bike
If your using the guages then obviously this wont be a problem. Just move the throttle more slowly to avoid the high vacuum condition (hey yer only syncing the carbs - were not at streetfighters now showing off).
If it is running properly all 4 guages will give out the same reading or ideally very close. If they're not, its time to sync the things.
Remember those 3 screws?? Depending where the reading is out make an adjustment to the neccesary screw..... A little adjustment counts for a big change thus you shouldn't have to turn the screw much. Watch the manometer closely and try to get the 2 carbs as close as possible.
You will need to wait until I get a pic posted but you can work off this:
Carb A Carb C Carb B Carb
Imagine the word carb.... is the carbs and the a.b.c are the screws, make the adjustments in the following order.
A to sync carb 3 to carb 4
B to sync carb 1 to carb 2
And C to sync the left and right pair to each other.
When it's all done and correct, remove the manometer and replace the rubber caps.... set the idle screw back to 1,000 - 1200 RPM.
Now put on yer gear and go tear up some tarmac!
If the synch was out to begin with you should notice a difference and a much smoother idle and ya just saved your self a few pints by not paying some greace monkey to do it for you!!