Mother of all non start mysteries

Hello Fellow Husaberg people. Thanks in advance to you all for all the great information I've so far used to work on my 2009 FE 570

My problem:

My bike wont start, sometimes it will if i crank it over for 30 seconds or more it will backfire and eventually start. it was running ok (a bit rich) but started dieing off throttle for example when I approached a intersection and rolled off.
then when I would try to restart the bike it wouldn't go and I'd have to tow it home.
I'm currently trying to start it on a lithium battery from a larger bike so I don't need to charge the small FE570 battery so often.

I've so far changed:
Fuel pump
Fuel filter
Fuel line
Injector
Spark plug
Spark plug cap

And checked:
- Spark is pressent
- Tested the stator, regulator, pulsar coil and Ignition coil and all are showing reading which they should.
- Fuel pressure is a solid 52 psi
- Pulled out the wiring harness and checked for rubbed wires, shorts etc
- Checked the kill switch (inspected and unplugged)
- Checked all grounding points and lines and all are good.
- Visually checked down the throttle body and the injector is firing
- Valve clearances checked
- Cam chain checked
- Fuel in the tank is fresh
- Decompression valve checked
- Made a straight fuel rail connection for more direct fuel delivery like the ones made by Dave Simon- KTM/HUSKY.com

I can't measure the engines compression but I can feel by putting it in gear and turning the wheel that is has at least good compression.

... think thats it


So I have Spark, Fuel and compression..... what else do I need?!
It does feel like the bike is running rich but it shouldn't stop it from running at all?!

Would appreciate any thoughts or advice

I've replaced the TPS and re adjusted it to stock 0.601v, I've replaced the mahle kl 79 filter with this one:
https://www.bestdualsportbikes.com/in-tank-fuel-filter-ktm-husqvarna

Which is the second filter? the course strainer on the bottom of the fuel pump?

I've checked the throttle play and its as it should be 3mm if i remember correctly.

Update: I've tried Areostart and it will start straight away and then run perfectly and once warm will start no problem but still wont cold start without the aerostart

Dealer suggested potentially something up with the programming of the start procedure....

Ah sorry I misread, Which is the TPI?

Sam

It doesn't have the stock fuel rail with the small screen in it so thats not the issue. Fuel pressure is correct to the rail/ injector

I haven't played around to much with the TPS I'll give that a go.

Its at a local ktm dealer at the moment getting a leak down test done. slightly low compression could cause hard or no starting but ok running once there is some heat in the chamber due to the slight swelling of the seals etc. so see how we go

Yeah this is where my mind was going aside from a potential compression problem, I was getting a wet plug sometimes, but i wasn't sure if this was because I was turning it over so many time without a fire..?

I the compression test comes back as good then you could be on the money.

How would I test for injector timing?

Sam

Yeah the mechanism can get sticky, I've checked mine and its fine.

Yeah I checked the pulsar sensor, correct resistance 100 ohm and no resistance back to the ECU