Hi Help wanted here in sunny wrexham does anybody at all on here no how to balance the carbs on my xj.It wants to start but keeps cutting out or sometimes just will not start, When i do get it going it splutters a bit and just will not tick over also it sometimes back fires and flames shoot out of the exsaust i have been told its over fuelin. So if anybody would like a ride down here to help i would be more then greatful cheers.

Have you Checked the choke is not stuck on                                                                                                                                                                             

sounds like you need to clean the jets out. due to petrol being so crap you get build up of gum round the jets. on the balancing side if i remember xj had a special tool that was needed to balance the carbs. carb balencing. jp morgan's balancers are great very easy to use comes with everything you need. If you have your bike stored over the winter put some stabyl in the fuel. triumph motorcycles use it. it's about £10 a bottle but does a few tanks of fuel

just seen that your in wrexham, nip and see eldon at the old barracks. he brakes bikes and maybe able to give you a bit of advice. have a look around he has some very nice machines that he has collect. he has a very nice hurricane there as well as a v-twin 1000cc matchless

Cant help you with balancing but try turning the fuel tap to off overnight just in case fuel is seeping through whilst the bike is standing.                                                                                                                                                                               

my last bike was the xj 750 - so i bought the haynes manual for it - it also covers the 650 - if yours is like mine was 1980 -1984
if so i can look up what it says about the carbs and post it back to you - let me know if that would be any good 2 ya m8

ok here goes - i looked it up anyway this is going to take some typing - esp 1 fingered - lol but hey heres goes
carb synchronisation - the procedure for synchronizing the carbs on the 750 cc and later 650cc models is slightly complicated by the yics passages. since the inlet ports are interconnected it is impossible to abtain individual vacuum gauge readings using the usaual approach. to overcome this, yamaha produce a special tool in the form of a long rodwith a locking handle and seals along its length. before synchronisation takes place, oneof the two end plugs in the main yics passage is removed and the tool ( part number 90890-04068 ) is inserted and locked in place. the tool effectively blanks off the yics system to allow normal synchronisation adjustment

hope that helps a bit - when i had mine i always had the start it with the choke - winter or summer - but once it warmed up it was fine

I owned a xj 750 for many years, And from the symptoms you describe it sounds as if your one or more needle valves are sticking open causing carb flooding, Remove and strip your carbs and give them a good clean. get yourself a workshop manual before you start,

It is possible to balance the carbs on xj yics models without the blanking tool, you will get them somewhere near, but not using it makes fine tuning impossible ,

I made a yics tool from a long length of aluminium bar, i got a mate to machine some groves for O rings to sit in , spaced dead centre  between the carbs , worked a treat.