getting trouble with getting the bike to fire on 4 cylinders.seems to be running rich on number 2 cylinder.
should i clean the carbs,or what else can i do,ive had this problem before got a hotter plug in (7).
checked vave clearances,could it be a worn valve guide leaking oil into the cylinder?
or is it probably a carb issue,got a good spark,driving me to distraction this.

 

Be careful on going too hot of a plug. A simple leak down test may help you on your valve question but you did not really describe what the fouled plug looked like very well. A lot of oil? Is the ride smoking and consuming oil when cold? Is the ride hard starting after sitting? What is the mileage on your z650?

Generally, I have had more issues with a float being pin holed or not set correctly and needles/seats due to age which seeps extra fuel into that cylinder than anything.

Welcome to KF

 

If 3 of the plugs are good, don't run a hotter plug in just one cylinder. Agree with Drag^ sounds like a carb issue. Carbs are in good sync? Are you seeing a wet deposit, or a soot deposit on the "rich" cylinder plug?

 

the plug is a sooty black colour sometimes wet,mileage is 54000 miles,i changed the piston rings about 7000 miles ago.
its not hard to start starts really well,although may be useing a little oil, there is some smoke now and then ,but not always.
ive got the carbs off and cleaning all the jets up,and blowing through the airways with compresed air.
also going to check the fuel levels in the float bowls,if it was slightly high in that carb would that cause the problem?

 

Inspect the floats, the float height and the float needle and seat all at the same time to help rule things out while everything is right there and handy.

With 7k on the rings only and nothing else done, a leak down still sounds like a reasonable troubleshoot with the engine having 54k on it.

 

what is actually a leak down?oil from the head ?
ive mADE A CARB FUEL HEIGHT thing,so am checking them next.

 

You're SURE the #2 plug is firing (i.e. getting GOOD spark?) No "short circuit" sparking to frame, etc.?

 

any pictures yet?

 

checked compression 3 cylinders have got only about 100 psi is this too low or passable.

 

What about the 4th? What kind of reading (PSI) are you getting? Guessing this is the "bad" cylinder?