'79 KZ650b3 Not Starting

All of a sudden one afternoon last week my '79 650 decided not to start. I thought maybe it was a spark plug issue so I changed all four. Still nothing. Battery is good and there were a few times when it sounded like the bike wanted to start but was just missing that last little push. I'm no mechanic and I am completely lost as to what to try next. Any suggestions appreciated.
Some background... the bike has been used without any problems on my daily commute of 25m each way and a few longer rides for the last 6 weeks. There were a handful of days where the bike took some persuading to start on the cold mornings.
Thanks.

Fuel on,full choke,and don't give it any throttle.
Are you getting spark to all 4 plugs?
Do you have an in-line fuel filter?
Are the carbs getting fuel?
Kink in the fuel line,perhaps?

Kill switch on?

try jiggling the key in the ignition,while you crank the engine over.You'll have to tie the clutch-lever,if it has a safety-switch,or get someone to hold it in for you,while you hit the start button with one hand,and jiggle the key with the other.

Air filter been cleaned?

You need spark,fuel and air,so make sure you're getting all that.

Sometimes,the vent on the gas-cap will clog,so try it with the gas-cap open.

Check those,and report back...

Thanks.
How do I check if I'm getting spark to all four plugs?
In line fuel filter? how do I find that out?

dct wrote:

...In line fuel filter? how do I find that out?

Click here to see a selection of inline fuel filters available from Z1E > Z1E Inline Fuel Filters

The inline filter is an aftermarket item located in the fuel line between the petcock and carb. Sometimes there are two inline filters, depending on layout of the fuel lines.

Inline fuel filters provide supplementary enhanced filtration far superior to the screen filters incorporated into the petcock. The petcock screens (even when in good condition) do indeed help but unfortunately may allow smaller grit and crud to flow on through toward the carbs.


As Sandy mentioned, fuel must be getting to the carbs.

If an inline filter gets sufficiently clogged with all the crud it's continually filtering from the fuel passing through it, the filter may no longer allow enough fuel to flow through, so that the filter is actually blocking fuel supply to the carbs.

It's easy to check for sufficient fuel flow through the filter. And if in doubt, replace the filter.

Good Luck!

dct wrote:

Thanks.
How do I check if I'm getting spark to all four plugs?

Pull all 4 plugs out,and reconnect them to the proper plug wires.
Now take all 4 plugs,and rest them on the engine,somewhere where they'll stay.Make sure that the electrode is making contact to the metal surface of the engine(this will ground them out,completing the electrical loop).
Make sure the bike is in neutral,and turn the engine over.
Turn off some lights though,so you can easily see if the plugs ARE getting spark.

You MIGHT have to remove the tank,to get at the #2 and #3 plugs though,but you should do it anyway,so you can look at the plug wires,and where they connect to the coils(which are mounted under the tank,to the frame).
Check the plug wires carefully,to see if they are cracked,or if the connections look bad.
It COULD be something as simple as replacing the plug wires,and if that is the case,the wires are factory connected,directly to the coils(one piece),but you CAN get splicers to adapt new plug wires,so don't let that confuse you.
If it comes to that,then we'll explain how to use the splicers,and where to get them.

Good luck.

Thanks for all the input.
I attempted the suggestions last night and here's the latest...
No inline fuel filter.
Checked all lines as best I could and nothing seems kinked.
Pulled the plugs - no spark on any of them (maybe I did something wrong?) When I was trying each plug the starter motor (not sure if that is what it is?) became more sluggish / weaker.
Still need to check the air filter.
Suggestions?

if you are not getting any spark, the first stop should be to see if you have voltage at the coils, it may be something as simple as a bad connection.
also charge the battery, it needs to be hot

You drained your battery,from turning it over.
Get the battery charged with a trickle-charger(no more than 2 amp).
Ok,so you've figured out that you're getting no spark to the plugs,at this point.
For both or your coils to pack it in at the same time,is unlikely.
Have you been messing around with any wires at all,in behind the side-cover?

Up around the headlight,you may have disconnected some wires?
Did you try jiggling the key,while you were turning it over?

Need more info,bud.

Regarding plugs not sparking --

Would recharge battery and then measure voltage at coil primary terminals with ignition turned on. This is to assure that the coils are receiving voltage.

The problem may be something else, but the coils must receive voltage in order to function, so this is a good preliminary thing to check.

Good Luck!

Edit -- I just keep getting older and slower! :lol:

:laugh: @ Patton.

Hey...some women LIKE older and slower.:laugh: