KZ750 won't start, might give up.

Not really sure what to do at this point.

My KZ750 was running when I put the engine in - it started first try and ran well. It was fitted it with a Shorai LiFePo battery, K&N pod filters with a DynoJet stage 3 kit, and a Delkevic exhaust. It worked okay, but it was running lean. I upped the jets to #70 Primary Main jet and a #140 Secondary main based on experience of people on this site.

This made running worse as it was popping at the carbs and I couldn't get the bike to run long enough to try to sync the carbs. Suddenly it won't start all together.

Assuming the pod filters were the problem and were never going to work, I spent the money on an air box, new rubber hoses, a K&N high flow air filter for the box, jetted the carbs back down to the DynoJet stage 3 (stock Primary main, #136 Secondary main) and the bike STILL WON'T START.

Here's what I've done:

Delkevic 4 to 1 exhaust - primary baffle removed
New NGK spark plugs
New head gasket
New cam cover gasket
Shorai LFX battery with new R/R
Fixed CDI ignitor wiring - wires were disconnected from corrosion so I soldered new wires
Stock air box with K&N high flow air filter
New Carb and air box boots
New petcock
Clean gas tank
Checked cold compression - all cylinders 140psi
DynoJet stage 3 kit - stock Primary main jet, #136 Secondary main jet, followed DynoJet instructions
Mixture screw 3 turns (DynoJet says 3.5, stock should be 2.5 so I figure in the middle is safe to start)
Checked Valve clearance - all within spec
Golan inline fuel filter
Cleaned carbs
Bench synced carbs

It turns over but just won't start.

Any idea if I'm missing something obvious?

you need 3 things for a bike to run, compression, spark, and fuel. You have verified compression, Can you verifiy spark and fuel?
To check spark, remove all the spark plugs. One at a time, insert them into the different spark plug wire boots and touch them to the engine so they ground. As you crank it over you should be able to see a fat blue spark.

Replace the IC ignitor.

Fixed CDI ignitor wiring - wires were disconnected from corrosion so I soldered new wires

Did you really fix them?
Doesn't sound like it to me.

What happens if you spray starter fluid in the airbox ?

Greybeard wrote: Fixed CDI ignitor wiring - wires were disconnected from corrosion so I soldered new wires

Did you really fix them?
Doesn't sound like it to me.

It started and ran after I fixed them.

baldy110 wrote: Replace the IC ignitor.

A new one is $500-$700. Know of any aftermarket ones? I could maybe gamble with another cruddy one from eBay...

JR wrote: What happens if you spray starter fluid in the airbox ?

I can give that a try and see if that helps. Just confused why it ran originally with the pods and less than optimal jetting, but now it won't run with the stock airbox and more appropriate jetting.

I assume you had the tank off to do the airbox and carbs off, you may have inadvertently disconnected the coils maybe, earthed some thing that shouldnt be earthed. As previously mentioned, check you have a spark, check you have fuel and check you have compression. If all three of those are present at the correct time it will run.
Maybe a silly oversight like kill switch off, obvious I know, but wouldn't be the first time its happened!

Used IC ignitors are cheap. Anytime there is corrosion on the wires I have also found the IC box is also bad so to make sure I get another one. Just trying to eliminate a possible problem. The Kawasaki IC ignitor ignition is very good and reliable. I've never had a used one not work unless they've been tinkered with or corroded. The ones from the 1000's will also work for you.

This link will show how to make one for dirt cheap. The tricky part is getting the right modules as they are getting harder to find.
s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html

When you check for spark on the bike, you must make sure all four spark plug wires have a path to the engine. That is make sure all four plugs are connected to the plug wires and all four plugs are resting on the engine. If you don't do that, you will damage a coil or the igniter.



Here's a diagram if you want to bench test the igniter and pickups off the bike to eliminate possible wiring issues that my exist on the bike.

I wasn't around much this weekend to tinker, but on Friday I checked to make sure I had spark in all 4 plugs. It was a good dark blue spark.

I re-checked compression just in case and it was still strong across all 4 cylinders. Fuel flows. Battery was charged and engine turns over, but it still didn't start.

DoctoRot wrote: you need 3 things for a bike to run, compression, spark, and fuel. You have verified compression, Can you verifiy spark and fuel?
To check spark, remove all the spark plugs. One at a time, insert them into the different spark plug wire boots and touch them to the engine so they ground. As you crank it over you should be able to see a fat blue spark.

Actually 4 things are needed to make an internal combustion engine run. You forgot oxygen. The fuel/air ratio needs to be somewhere around 14.7:1 for it to ignite. If the ratio is much over or under this ratio it will not fire. This is the reason that a electric fuel pump will work inside a fuel tank.. the fuel / air ratio is wayyyy too fat to ignite the fuel inside the tank.

The sequence is suck, squeeze, bang and blow. (intake, compress, ignite, exhaust) I had a T-shirt that said this once.. everyone thought it was a dirty meaning, but it actually described the 4 stroke internal combustion motor sequence of events. :evil:

A flooded or fuel starved engine will not run. If there is indeed fuel and spark there, it is most likely flooded. A shot of starting fluid into the intake air will tell you if it's fuel starved. If flooded, it will not fire on the either. Wet plugs will a not fire nor spark. The wet plug shunts the electric current to "ground" without sparking the gap.