1978 KZ650 - no start

Hi,

I've got a customer bike in my shop (1978 KZ650) that was an absolute basket case when I got it.  I've gone through the wiring harness and finally have it where it cranks over, has spark, etc.  It has one of those goofy Dyna S ignitions instead of the good ol' points, but I did set the timing properly.  When cranking the plugs get wet and it has good spark, but it won't fire.  It has 17.5 pilot jets, 107.5 mains.  Pods and a 4 into one (unfortunately).

I have a lot of experience with Keihin carbs but not a lot with Mukunis (other than single cylinders).  What should I be looking at next?

Thanks for the help!

Hello.

If you had the cam off the timing advancer, it is possible to reassemble it 180 degrees off/half a turn off.
You will still get good spark, but at the wrong time.
Easy enough to swap back, or you can possibly reverse the coil feed wires.

The main jets may need to be a little larger.
But she should still start first.
 

Hmm, I didn't remove the cam (assumed it was installed correctly...), but probably should have.  I'll check into that and see if that's what's going on!

Ok, verified the timing is not 180 out.  It sounds kinda like 1 cylinder is trying to fire but the other 3 are not.

In general, dry, ambient air at sea level contains about 21% oxygen, 78% Nitrogen and trace amounts of Argon, CO2 and other gases. Gasoline requires oxygen to burn. Since oxygen is only about 1/5 of air’s volume, an engine must intake about 5 times more air than gas to get the oxygen it needs to support the combustion of fuel. Keep in mind that lean mixtures (at about 18 to 1 parts air to fuel or higher) a spark will not ignite the mix and like wise rich mixtures (at about 10 to 1 or higher) will also not ignite the mix. Those numbers change depending upon elevation, temp and humidity.

The jetting you indicate is much like what many of us attempted to overcome the lean spot between idle and throttle movement beyond idle in the past, not to say it was correct but rather what many of us did. It appears you have spark (may not be at the correct time) fuel as plugs are wet. Have you checked compression? What shape are the carb holders, rubber flanges between carb and head? What shape are the enricher/choke plungers pads in? You could have too much fuel or too much air. I would also suggest you see what the voltage to the coils is. It needs to be very close to full battery voltage.

 

Coil voltage - should have thought about that.  Checked it and it's 9.5 at each coil.  Trusted some junctions the builder made in the wiring harness, should have just cut those out to begin with.  Cut out those junctions and soldered the coil power wires up and now it's getting 11.8v at the coil.

That being said, it's still not firing.  If I reverse the coil connections I get a lot of backfiring (a sign of being 180 out) so the coils are connected correctly.  I'm going to do a compression test shortly.

Compression is between 68 and 75psi on each cylinder...

Guess I'll take the valve cover off and check valve clearance.

Any further results to share with us?

Doing things backwards.

First, maintenance: check valve clearance, rebuild carbs, change plugs, brake system rebuild and clean out, clean the fuel tank, etc.  All the stuff in the factory Kawasaki manual.

Second, try to start the bike.

Not the other way around.

Well, the guy said it was running when he brought it in, it just had electrical issues and needed carb work.  I cleaned out the carbs and resolved all the electrical issues, then found all this.  If it was my bike, yeah I'd do all the maintenance first.  When you're billable, you can't be charging that much time for stuff the customer didn't ask for.

gd4now wrote:

Any further results to share with us?
 

Had some family and friends come down for the 4th so took a few days off for the holidays.  Checked the valves and here are my findings.  With these as tight as they are, I'm guessing that's my compression loss issue.  All values are metric and in mm.

1 - .08
2 - .09
3 - .04
4 - .04
5 - .09
6 - <.04 (my feelers don't go below .04)
7 - .09
8 - .08

My full time job has been keeping me too busy to be able to get in the shop during the week.  Finally getting out to work on this again.  Popped the cams out and checked the shims.  I'm having some difficulty understanding the chart.

So for instance here are the values

5 - .09mm - 260 shim
6 - <.04mm - 260 shim
7 - .09mm - 265 shim
8 - .08mm - 260 shim

So 5, 7, and 8 are /technically/ in spec but just barely.  Would it be better to go to these shim values:

5 - 255
6 - 245
7 - 260
8 - 255

This is my first time dealing with this shim-under-bucket style valve.  I'm used to adjusting the tappet (Honda style).  Just want to make sure I do it right.