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TOPIC: 1981 KZ750 Ltd no spark, not starting

1981 KZ750 Ltd no spark, not starting 11 Apr 2017 14:16 #758976

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Hello, I'll try to keep this short and sweet and appreciate any thoughts.

I bought a 1981 Kz750 Ltd at the start of the year after passing my test which initially ran fine until it started cutting out, mostly when coming to a stop. I am new to riding, motorbikes, tinkering, etc but have been trying to solve my many problems through these forums and youtube. I think a list of the chain of events may help:

Bike cut out, more frequently as time passed
Bike failed to start
Cleaned carbs
Bike ran but eventually died and didn't start. Made horrible noise when trying to start.
Replaced clutch starter rollers, pins, springs ( great learning curve for a novice)
New oil filter
Bike ran but still randomly cut out
Checked for air leaks
Carb floats adjusted
New fuel filter
New battery
New spark plugs
Tested compression 100, 110, 110, 95 (dubious cheap compression tester)
Bike died, fuse had blown, started again with new fuse but died a few miles down the road. New fuse, no difference
No spark on any plug
Two new coils, still no spark
Aaaaaaaaaaaaaaaggggggghhhhhh!!!!!!

I am loving riding, loving having a KZ750 LTD, loving tinkering but just need to get this beauty back on the road. Summer is pretty much here! As stated, I am a novice, this is all new to me but any help is much appreciated.

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1981 KZ750 Ltd no spark, not starting 11 Apr 2017 18:34 #758986

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Check IC Igniter.
I have a 1980 Kawasaki KZ750 Ltd. I bought new. I recently managed to get it out of my garage after 28 years and put it on the road again (2010). I feel like a kid all over again. Since I have acquired 3 78 KZ1000 Ltd, 1 1981 KZ1000 Ltd, and another 1980 KZ750 Ltd. Love the LTD's.
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1981 KZ750 Ltd no spark, not starting 12 Apr 2017 08:38 #759023

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Condition of plug wires?

Good Fortune!:)
1973 Z1
KZ900 LTD
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1981 KZ750 Ltd no spark, not starting 13 Apr 2017 14:05 #759124

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Bear with me if I get long winded here...
35+ years ago I was a newly trained electronics technician fixing Printed Circuit Boards (PCB). There were several other Techs and we all sat at a row of benches fixing PCB's. There was an "actions taken" form where you documented the symptoms and trouble shooting steps, along with any components replaced. In theory, another tech could use this form to pick up where you left off.
Now over in the corner was a stack of PCB's that were commonly refereed to as the BFH's (Boards From He11). These were boards that had been worked and reworked so many times that everyone had given up. The actions taken forms were 10 to 15 pages long and every component had been replaced at some point.
One day I took one of these BFH's and spent an hour stripping, cleaning and re-soldering every connection. I put it on the test fixture and got a big green "PASSED"! A BFH was moved to the good pile! I repeated this process, fixing probably 90% of the BFH's, some of which that had been there for years. I didn't tell any one what I was doing until I had completed the stack. Rumors began to circulate about the Young Genius Tech who slayed the BFH stack.
The point of this story is 90% of electrical problems (especially intermittent ones like you described) are due to corrosion or poor contacts. Your wiring is 35+ years old and has spent it's life in a harsh environment. Spend an afternoon and clean /inspect all the connectors on your bike. Get some electrical contact cleaner (Deoxit is a popular choice) and a fine wire brush or glass fiber pen. If the pins are deeply recessed and you can get to them, soak them with cleaner and remove/insert them several times. You may just slay your bike's BFH problem.

Good Luck
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1981 KZ750 Ltd no spark, not starting 17 Apr 2017 08:22 #759398

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Thanks for the advice. The plug wires are good. The IC Igniter I did suspect but it sounds like I'll only find out if I buy a replacement. The connections I will clean and check.
I have tested the connector that goes to the pickup coils and the readings look good. The connector to the ignition coil, however, doesn't read anything when I test the ground wire (black/yellow). So, I assume there is a connection fault somewhere but I don't really know where to start. I don't know where that wire goes as everything is taped up.
Any words of wisdom greatly appreciated.

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1981 KZ750 Ltd no spark, not starting 17 Apr 2017 11:45 #759422

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You need to have a wiring diagram for your bike, the 1980 KZ750 LTD also known as H1 is the same as the 1981 KZ750 LTD. also known as
H2, if you don't have the service manual, download the manual that is available here and follow the wires according to the diagram and I'm pretty sure you are going to find where the problem is, it can easily be a broken wire or bad connection..
I have a 1980 Kawasaki KZ750 Ltd. I bought new. I recently managed to get it out of my garage after 28 years and put it on the road again (2010). I feel like a kid all over again. Since I have acquired 3 78 KZ1000 Ltd, 1 1981 KZ1000 Ltd, and another 1980 KZ750 Ltd. Love the LTD's.
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1981 KZ750 Ltd no spark, not starting 17 Apr 2017 12:05 #759424

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If you go to the home page here and scroll down you will find a list of shop manuals on the right hand side. Download the one listed as gpz 750 base manual as that will cover your model. The ignition section will have a trouble shooting flow chart. Wiring diagrams in manual are black and white and as suck not great. Use google to find a colour one.

You have already done some trouble shooting so you could continue by checking if there is power ( 12 volts) at the coils. Remove gss tank. Each coil will have a red wire and either a green or black wire connected. Red wire is power. With ignition switched on set your multi meter to 20 volts dc and put + probe on one red wire and - probe on frame or engine. What voltage are you seeing?

If zero voltage then power for the ignition goes from battery to fuse to ignition switch to kill switch to coil and fault is probably between ignition switch and coils.

If you have 12 volts at coil then problem is probably the signal . Green and or black wire , ignitor, pulse coils or the connectors in between.

The manual and colour wiring diagram will help you here.

Good luck
Edit . Looks like it took me 20 minutes to write that.
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1981 KZ750 Ltd no spark, not starting 19 Apr 2017 12:31 #759615

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Thanks for your time. The test showed 12 volts so it appears to be the igniter or connectors. Does anyone know if an IC Igniter off a KZ 1100 Spectre is compatible with a KZ750 Ltd? The one I have seen looks identical, the wires, everything.

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1981 KZ750 Ltd no spark, not starting 19 Apr 2017 14:08 #759620

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A quick look at kawasaki.com , owner info, parts diagrams shows ignitor part# 21119-1041 to be in common for for both 1981 kz750 LTD and 82 Spectre 1100
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1981 KZ750 Ltd no spark, not starting 22 Apr 2017 04:53 #759868

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It's alive...........just!

So, I put a new connector with new pins on the wires going to the IC Igniter as it was corroded. The readings from both plugs to the igniter checked out so I assumed the igniter was faulty.

I replaced the igniter with one I found which looks identical but is from a KZ1100 Spectre. The part number on my dead one is 21119-1020, the replacement is 21119-104?. Not sure if this makes a difference. Anyway, the bike fired up but is running on cylinders 2 and 3 only. There is no spark at 1 and 4.

Both coils are new and primary readings are 3.6 ohm. The secondary readings are 16 kohm, with the caps on 27 ohm.

I tested both coils as suggested by JR and both read almost 12V.

As this is all new to me it's a bit of a guessing game but finding your input very helpful. So, guessing again, is it now likely to be a connection failure? Low compression?

When it does start up, there does seem to be a kind of knocking noise from the engine.

Apologies for my lack of knowledge.

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1981 KZ750 Ltd no spark, not starting 22 Apr 2017 10:56 #759894

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Sounds like you are making progress

When it does start up, there does seem to be a kind of knocking noise from the engine.


Normal for a motor running on only 2 cylinders

Both coils are new and primary readings are 3.6 ohm. The secondary readings are 16 kohm, with the caps on 27 ohm.


Stock coils have lower primary resistance .



I have no idea what impact your 3.6 ohm coils may have on other components of your ignition system

Having said that you could try the following
Pull all 4 spark plugs and ground them on the engine while connected to their plug caps and plug wires. Hit the starter button. Have you spark on all 4 plugs including the 1 - 4 plugs ?
If yes then problem is valves compression or fuel/carbs.

If still no spark on 1-4 plugs then swap the black and green wires to the other coil. It does not matter if you swap the red wires to the other coil as these both carry battery voltage all the time ignition is on. it does matter which coil the green is connected to and which coil te blackis connected to. I just cant remember if green is for 1-4 and black is for 2-3 or vice versa.
In swapping wires you are trying to see if the problem follows the wires.
With black and green swapped hit the starter button again. Did the problem follow the colored wire to the 1 - 4 coil?
If no then problem is with plugs, plug caps, coil etc.
If yes then trace back that colored wire - Is there continuity (ohms) from wire at coil to connector at ignitor? Is there continuity from ignitor to the pick-up coil under the CD sized cover on the right hand end of the crank?
Crack open the manual and follow tests for ignitor and pick-up coil

Good luck
PS dont forget to swap back the coil wires to where they should be :)
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1981 KZ750 Ltd no spark, not starting 24 Apr 2017 13:32 #760151

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Thanks again JR! Not quite there yet but you've really helped.

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?

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

I have read that they should be higher than that but I'm not sure what a cold test should produce. But as the bike does run I'm assuming these results aren't too bad as they are all similar to each other.

With all pipes hot I thought Id take it for a quick test ride. I got about 50m down the road before it cut out.

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

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1981 KZ750 Ltd no spark, not starting 24 Apr 2017 17:44 #760166

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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
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1981 KZ750 Ltd no spark, not starting 24 Apr 2017 17:53 #760167

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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
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1981 KZ750 Ltd no spark, not starting 25 Apr 2017 12:59 #760235

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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
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1981 KZ750 Ltd no spark, not starting 26 Apr 2017 15:52 #760331

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Eventually, 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.
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1981 KZ750 Ltd no spark, not starting 30 Apr 2017 11:34 #760774

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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
8) 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.

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1981 KZ750 Ltd no spark, not starting 30 Apr 2017 16:00 #760798

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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.
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1981 KZ750 Ltd no spark, not starting 18 May 2017 01:36 #762118

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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!
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1981 KZ750 Ltd no spark, not starting 18 May 2017 14:06 #762159

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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.
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