Difficulty balancing carbs ,am using carbtune but one carb has very low vacum reading.Fazer 600fzs model.Seals ok on inlet/outlet side of carbs,Possible causes and cures.Thanks

the vaccum pipe is connected to inlet manifold that goes to the charger,it is the same vaccum hose that used to balance the carbs.

Most chainsaw issues are fuel related, basically you need clean fuel/oil mix in the fuel tank, a breather in the tank to stop a vacume forming,a fuel hose with a filter on the end to deliver fuel to the carb, you have an all position diaphram carb, this is for two reason, the fuel is below the carb so there is no gravity feed for the fuel, and the machine is used in many different positions which would make a standard carb flood, there will be a pulse tube to the carb, this takes the positive and negative pulse from the piston riseing and falling to the pump diaphram in the carb, the diaphram pulsates and so draws fuel up the delivery pipe, the flip side of the carb is the fuel metering side, here you have a inlet needle, and a spring loaded metering lever, if the chamber is empty atmospheric pressure pushes the diaphram down on the metering lever allowing fuel to flow in, once the chamber is full, the diaphram expands, the needle shuts, and fuel flow is stopped, within the carb body is low and high speed jets, the fuel is controlled to these via two screws, a H screw and a L screw, the L screw contols idle and revs up to half speed, and the H screw controls the maximum revs, atomised fuel is taken into the bottom of the engine where it is compressed and forced up the transfer ports and above the piston, this is why you need air tight seals on the crankshaft. the fresh charge is compressed, a spark occurs via a magnet on the flywhell passing the core of the ignition unit, and so a power stroke is delivered. So the filter on the fuel hose needs to be clean, the hose needs to be sound with no leaks, the carb diaphrams need to be in good condition, the jet screws need to be set correctly, the crank seals need to be air tight, and you need a spark at the correct time to ignitr the fresh fuel charge,

Usually the line with the filter on it that comes from the tank goes to carb. inlet first which is most likely close to the bottom side of the carb.nearest to the engine,then the outlet or return line on the carb.goes to the inlet side of the primer and the outlet side of the primer goes back to the tank. The primer draws fuel through the carb to the primer to the tank if its not? then correct the line connections until it does

Check your plugs. If all four are sparking then your carbs are out of sync. They will need to be re-balanced.

If you are capabable in doing this job your self, you will need a screwdriver that fits your adjuster screws and a CarbTune Carb balancer.
Remove your tank and airbox.
You should see the flaps inside your carbs. These should open when you move your throttle.
Start on the outside carbs to get them balanced with the 2 centre ones.
To start, unscrew the adjusters all the way out. then screw them in until the 2 outer carbs move at the same time as the inner 2 carbs
Once this is done then adjust the centre balancer to syncronise the 2 left hand carbs to the 2 right hand carbs.
Now if you have done this correctly, all four carbs should open at the exact same time.
If you have a Carbtune balancer, remove the plugs from the top of your inlet manifold and plug in the hoses from the carbtune balancer.
Start the engine and adjust the screws until the weights inside the Carbtune balancer all read the same.
Once done, remove the balancer, replace the plugs into the inlet manifold, refit the airbox and tank and it should run so much better.

If your not 100% confident to unertake this job yourself, take the bike to your local dealer and ask to have the carbs balanced.

Ok. If the tach is being radicl and the engine joins in we have a clear indiction of a loose or otherwise faulty connection at the coil or a defectine coil itself.. Chk that connection poit for any descrepencies , Good Luck

if the carbs are properly balanced the only thing it can be is the timeing. it could be a littler advanced or turned back check that

I have an 89 Katana and don't know where the two vacuum lines on the top of the carbs go