KLE500 cold start?

I have a KLE500 1991 and suddenly developed a cold start problem. Kawasaki said it's only spark plugs which I replaced and no change.

I have checked the fuel lines, battery, solenoid and carbs but no sign of default there.

The bike is on 54000km and has a bad tapet cover oil leak(already order the gasket), so bad that there was a bunch of oil around the spark plugs.

can the oil leak cause it or maybe because the valves need to be adjusted?

Please help