Struggles to start

G'day smart people,

I've got a ZX14 engine in a dirt buggy.

This is the second engine I've tuned in a buggy.

The engine starts and runs very well when I jump start it from a car battery. However it refuses to start using a motorbike battery.

I've done about an hour of tuning and the fuel map is all running bang on the lambda targets. Drives and revs great all the way to 10k rpm.

It seems to turn over fine, with the occasional stutter as if the timing is too advanced under cranking. It doesn't do this jump starting it.

I've tried 3 batteries, two 11's and a 13. I don't know what the numbers mean. The guy at the bike shop said a 13 is what the ZX 14 runs. All E batteries do the same thing.

As I'm restricted for space it needs to be a motorbike battery.

The engine has a 24 -2 crank trigger and a cam sync sensor. Is it possible that I have this wrong in the ECU setup (haltech elite)

Without the extra battery power it just won't start and keeps cranking until the battery goes flat.

Could it be a fuel issue at cranking and how do I adjust it?

Anything else it might be that I've overlooked?

Any help would be greatly appreciated

It sounds like a trigger issue to me. A common issue with high compression low inertia motorcycle engines is the large variation in cranking speed as each piston comes up to TDC compression can make it difficult for some ecu's to identify the missing tooth gap. Since you mention what sounds like a kick-back event from a spark occurring in the wrong place and it starts ok with a larger battery those symptoms give me the feeling that this may be your problem.

Its been a long time since I've tuned an elite so I dont remember what they have for trigger diagnostics, but typically you would start by logging/monitoring trigger related channels such as trigger state or sync level, crank angle etc to get a feel if it is syncing and staying synced. I dont remember how much info their trigger scope tool gives but it would be worth doing a capture or two when cranking, compare a good start to a no start etc. You will probably need to discuss diagnosis with Haltech support for suggestions more specific to their software.

If it is a gap detection issue and they dont have any optional trigger settings such as tooth tolerance or post gap validation to improve detection then all you can do is take all precautions to make cranking speed as fast and as smooth as possible. Bear in mind it is going to be worse on a cold winter day too. Precautions would be things like getting the largest CCA battery you can fit - lithium will give more grunt per unit volume. Minimise voltage drop to the starter by using large good quality, properly crimped battery cables, make sure the negative cable goes directly from batt to the starter body, us a larger good quality starter solenoid, not the tiny OEM bike one. Also be aware, most sport bike starters have a spag clutch in them so they can start to slip if its had a hard life from kick backs etc.

In our race cars with large displacement bike engines (Hayabusa, ZX-14, etc), we sometimes run two small batteries in series (so 24V) to the starter. You will often have to charge the second battery separately, but usually only need to do that between events.

LiFePO4 is a good suggestion for a single battery as well.

Checked all the signals and sync with the oscilloscope and everything reads correct.

Added more fuel to the cranking table between 10° and 50° coolant temp.

That got it to start cold but not once it warmed up.

Then I asked myself what could be the simplest answer.

So I pulled the starter apart and found its DEFINITELY the problem. Machine the armature and cleaned the stator, second hand set of brushes and it should now outlast The next thing to inevitable fail.

Thanks for the ideas and help, it led me to the problem