99 zx6r almost impossible to start… what next?

[ffunnyman]

The bike will rarely ever start. Most of the time the engine cranks and it just makes popping sounds from the muffler and out the carbs some.
When it does start it runs fine about 500-700rmp above where the idle should be. If I bring the idle down it starts backfiring. This sounded like it was too lean so I cleaned out the pilot jets. I have also replaced the battery.
What should I check next?

[Pleco]

Hello there.

First double check that you did not swap 2 plug leads around.

Regards

[ffunnyman]

damn your good.
thanks

[Pleco]

Your explanation was good. If you get popping sounds from the exhaust and the carbs, it means one plug is firing on the exhaust stroke, and another plug is firing on the intake stroke. That means they are firing out of order, and most likely the plug wires are swapped. I found this out rebuilding an old land rover, with no markings on the distributer to tell me which wire belongs to which plug. I actually had flames firing out the top of the carb!

Glad I could help.

Happy and safe travels.

Regards

[RichLees]

the zx uses "wasted spark" to reduce emissions. ie it fires just before top dead centre on every revolution. well-diagnosed, tho!

PS I was going to suggest opening the filler cap, dipping a rag in the fuel and setting fire to it ;-)