1981 KZ750 Ltd no spark, not starting

So I tried grounding all 4 spark plugs on the engine and to my surprise they all had a spark. I didn't expect it as I had grounded them individually about a thousand times, only getting a spark on 2 and 3. Is there a reason for this?

Cant think why works now but not in the .past. As stated before though i dont know what if any impsct your 3.6 ohm coils might have on your system.

I tested the compression (cold test) again and my results were 110, 105, 110, 105

Sounds awfully low. I'm not a mechanic just another 750 owner so cant say what the limit is before no fire. However if you have not checked valve clearances then it would be worth doing that now as tight valves not fully closing could cause low compression

A leak down test (search kzr) will tell you if valves or piston rings are cause of low compression.

So that leaves the carbs. I've taken them off again so I'll have a good look and check the float levels again.

If you go through the carbs again nessism has an excellent tutorial on carbs. There are no shortcuts with carbs.
Rather than float levels check fuel level using " clear tube method" . Search here. After cleaning and probing every single jet and oriface, setting correct fuel levels was the single best improvement i made to carbs and running

When 1 & 4 fail to fire are the plugs wet with gas ?

Glad to see you are making progress

Pedrosky750ltd wrote: ........
I tested the compression (cold test) again and my results were 110, 105, 110, 105..............

Since the engine runs I suggest you re-test the compression. Keep in mind that when you test compression you need to have all the spark plugs out, a fully charged battery, the throttle wide open, and the engine up to normal operating temperature. It would be instructive to all of us to see how much change there is in the readings under those conditions compared to testing a cold engine. Ed

I had my tank off today for some mixture adjustment and thought about your question

So I tried grounding all 4 spark plugs on the engine and to my surprise they all had a spark. I didn't expect it as I had grounded them individually about a thousand times, only getting a spark on 2 and 3. Is there a reason for this?

.... wondered if the cause might be something simple like loose connection etc.
You replaced the coils but what about the HT leads from coil to plug cap?
Perhaps not connected properly at coils?
Or plug caps not connected properly to the HT lead ? You could cut a 1/4 inch off the end of the HT lead and screw back on the plug cap. A common fix.
Perhaps dirty HT leads shorting out to ground? Wipe with WD40
Perhaps frayed trigger wire (black?)

Just some additional thoughts on where you might look

No eBay APP ID and/or Cert ID defined in Kunena configurationEventually, you will want coils with the correct primary resistance. As JR posted, you want coils in the 1.8 to 2.8 range. Usually they will measure around 2.2 to 2.6 ohms.

Here's what I think I'm using. They work well and are pretty cheap. (They don't have any manufacturer markings.)



But, before diving into the ignition, I would be more concerned with the low compression as Ed and JR mentioned.
Since the engine keeps dying and the compression is low, have you checked the valve clearance? That can cause the engine to die after warming up, but it usually won't be the cause of all four to be low.

After that is straightened out, then you can do some ignition troubleshooting by swapping components. You essentially have two ignition circuits on an inline-4 Kz.

When you check for spark on 1, number 4 must also be grounded (and vice versa) otherwise there is no complete path for the spark.
Same goes for 2 and 3.

You should check them in pairs. Leaving one unconnected while testing the other can damage the coil or the igniter.

So, I had a thought that maybe the fuel level in the floats could be too high. The bike would cut out when coming to a stop so I wondered if fuel was pouring in and flooding the engine. I originally read that the fuel level should be set to the level of the float bowl gasket to which I set them using the clear tube method, carbs off the bike using a spirit level, etc. I then read in the manual that they should be set to 4mm below the gasket line. I have now done this.

The bike started fine and idled nicely. When i moved the bike, just rolling it through the garden it cut out. It used to do this but also when coming to a stop. This made me think it's not the float level but must be something electrical.

As suggested, I have had a good look at the wiring. I stripped all the tape off, cleaned every connector, replacing some and taped it all back up. In doing this I came across a worn piece of insulation, revealing bare wire right next to the frame. Maybe this was the cause of the intermittent stalling?

I haven't started it up as I thought due to the low compression readings it would be an idea to check the valve clearances while the tank was off. So here they are;

Exhaust
1) - 0.04 (too tight for the feeler guage!!!!!)
2) 0.10
3) 0.10
4) 0.04
Intake
5) 0.08
6) 0.05
7) 0.08
0.08

Three are low, one especially.

While I was turning the engine over to get the clearances it made a hissing noise. I'm assuming this is not normal and is an air leak?

I passed my test and bought the bike to ride. It looks like I need to become a mechanic first!

As always, your words of wisdom are appreciated.

I originally read that the fuel level should be set to the level of the float bowl gasket to which I set them using the clear tube method, carbs off the bike using a spirit level, etc. I then read in the manual that they should be set to 4mm below the gasket line. I have now done this.

Everything you are doing will contribute to a better running bike when you eventually solve the current problem.

In doing this I came across a worn piece of insulation, revealing bare wire right next to the frame. Maybe this was the cause of the intermittent stalling?

Perhaps. My own experience with worn insulation and bare wire rubbing inside head light shell was the cause of a blown main fuse.

While I was turning the engine over to get the clearances it made a hissing noise. I'm assuming this is not normal and is an air leak

You have some compression so this would be normal. You might find it easier next time to rotate crank with plugs out but not a big deal

Assuming your valve clearances are in mm then yes you have 3 that you need to address. Clearance should be .08 - .18mm I believe. The workshop manual will be invaluable and has a cam cap tightening sequence on page 55.
Some tips
Before you remove a cam shaft use a zip tie through one of the holes in the camshaft sprocket and around the cam chain so you dont lose sprocket to chain relationship.
Dont move the crankshaft until you are finished.
You may need to loosen or remove the cam chain tensioner depending on what type tensioner you have - check manual.
Remove cam caps as per age 55 in the manual.
Lift and roll back the camshaft +sprocket+ cam chain.
I use a magnet to remove the bucket and shim.
I always had to use a digital caliper to measure current shim size. Shim size is printed on new shims but i've never had an old one with print remaining.
Refer to the table in the manual to find out what size you need to give you the correct clearance. Looks complicated but once you do it and see it it's pretty simple.
Let say you do the exhaust cam first then I would put it back and put back the cam caps without torquing and then do the inlet valves same way.
I get kawasaki shims from my local dealer. They come in a package of 2.
Kawasaki.com owner info, parts diagrams etc will show part numbers to order.

When you finally put everything back together pay special attention to the torque values for the camp cap bolts. Specs are in inch lbs (104) not ft lbs. This is just a hair beyond snug using a short wrench and I usually go a bit less. Something like 8 or 9 ft lbs which is 84 to 96 inch lbs.

When you do have it running and warmed up it would be good to check compression like 650Ed suggested.
Hang in there. I bought my 750 early July and over then next few months found wiring burned and shorted from battery acid due to lack of a breather tube, Plugged pilot bypass holes in the carbs. worn float valves, an oil pressure sensor that randomly shorted. Took me 3 months to learn what I had and to get the gremlins out but that was 13 years and 50,000 km ago and worth the experience. Still have the occasional problem but nothing that cant be handled using common tools.

At last! The wiring examined and cleaned, float levels adjusted and now shims changed and it runs nice and smooth. Thanks for all your advice, especially JR, cheers mate!

Great stuff !
You stuck with it, learned a bit, probably found that it wasn't that difficult and ended up with a great looking (nice photo) well running bike..
Thanks for letting us know how it turned out.