I just bought a 1977 kawasaki kz650. It ran fine when I got it home, and then I cleaned and sprayed some of the bike with a pressure washer. After that it started hard and now it doesn't start at all. I drained the gas and put new in, charged the battery, and cleaned the plugs. I don't why it won't start. It also badly backfires when trying to start it now. Could it be the timing or the carbs?

Carbs, you most likely got water in them...

How do I get the water out of the carbs? Do I have to clean them?

Get some carb cleaner... now if the carbs are old originals... IE not been cleaned and rebuilt since new maybe? I'd actually rebuild them from the ground up, new gasket sets and all... yeah you'll have to though take them off, maybe blow them out with compressed air and reassemble... don't know for sure but do the carbs have fuel bowls on them? Well water sinks, fuel floats... check those out for sure.

i just bought a 1977 kawasaki kz650. it ran fine when i got it home, and then i cleaned and sprayed some of the bike with a pressure washer. after that it started hard and now it doesn't start at all. i drained the gas and put new in, charged the battery, and cleaned the plugs. I don't why it won't start. it also badly backfires when trying to start it now. could it be the timing or the carbs?
I had a similar problem with a 85 900 ninja last year, turned out to be a spark plug hole was full of water and shorting out the bike. Used a rag to remove excess water and ran great right away, did take 4 days and a lot of unnecessary work to find. Good luck.

It sounds like you got your points wet while washing your bike. The points are located on the right side of the motor (as if you were sitting on the bike) under the cover that says Kawasaki on it. Try drying them out and then try to start it

i just bought a 1977 kawasaki kz650. it ran fine when i got it home, and then i cleaned and sprayed some of the bike with a pressure washer. after that it started hard and now it doesn't start at all. i drained the gas and put new in, charged the battery, and cleaned the plugs. I don't why it won't start. it also badly backfires when trying to start it now. could it be the timing or the carbs?
Hi,it looks like you drown one or 2 sets of points,behind the points cover,carefully insert a CLEAN piece of stiff paper between the points set and gently pull the paper to clean the points.

Replace the points with an electronic ignition.

Then if you get water in the carbs remove the drains screws one at a time. Put some silicone grease on the O-rings and re-install. Once that is done put fuel switch to 'prime' and wait 5 minutes. Start bike.

If the wires are shorting then replace the wires and coils if you're running a stock setup. Once those wires start cracking it's all down hill.

It is cheaper to replace the stock coils with after market racing coils and ignition.