GRiSO 1100 no start

Took my GRiSO 1100 apart to fix an oil leak.
While in there, I changed the alternator belt, all 4 plugs and new wires, changed the oring on the timing sensor.

Put it all back together, start the bike and I sounds like it's running on one cylinder. Headlight flashing and it will not idle.

Finally able to give some throttle and it sounds like it  learned up.
Let go of the throttle and bike dies.

Now all I get is a loud thunk when I hit the start button and dash goes blank.

Bike does have the MPH startus interuptus kit.
Battery load tested good.

Had to change the sump and spacer gaskets.
Put in 3 liters of oil.

Did notice some oil in the airbox... oil level is between low and full.

Just fishing for where to start looking as I cool off.

I’m clearly not one of the experts, who will hopefully come along soon. But, if it was me, I’d be checking the leads to all the plugs & caps etc. and everything you did there. Seems like that would be the only thing from your list of repairs that could cause those symptoms.

First rule of motorcycle maintenance..if it doesn't run after you did something, check what you just did...

Flashing headlight? Check the alternator belt is adjusted correctly.

Check Plug leads & caps. Did any of the shims fall off the phase sensor?

My phase senor was leaking...
I used a larger than stock oring.
Ordering the correct oring.

Would the minute extra thickness of the oring through it off that much?!?

Pulled po351 and 35codexes using guzzi diag.
Both pipes are equally warm.

Give both the battery terminals and the cable connectors that bolt to them a really good wire brushing, clean and coat them with Vaseline and try again.

Battery cables... both ends are clean.
Bike was running perfect before I mucked with it.

Looking at the plug wires I made and the phase sensor.
Would that oring being thicker really hose it up that much?

Yes

replaced the oring on the phase sensor with one that would lay in the channel like the original.
Got the bike to start and idle! Responded to throttle well and went back to idle like normal.

As the bike is idling, it momentarily wants to cut out and start again. 

The idle will go up for a second and back to normal.

Even when it starts it has difficulty starting, the bike used to catch and idle immediately.

Could my phase sensor be on the way out?

Possibly. Positioning is critical, however. The distance from the sensor to the phonic wheel needs to be 0.5mm - 0.7mm.
If the second o-ring is even marginally larger, there could be issues. You might need to check the air gap.

So here is where I am.
Bike starts idles... 
If I give it throttle and let it come back to idle, it sometimes cuts out for have a second and the headlight goes out every time. The dash never blanks out.
Then it catches again and idles nice.
Never happens when given throttle. Only when coming back to idle.

YES!
glad you're back on the road!

Excellent

Great news I have a similar issue but mine isn’t stalling just a bit of random tickover every now and again. So not sure if it is a stepper issue or the crank position sensor, which I have just swapped but checked the length and it is the same as the old one. And I correct in thinking you can test the stepper in Guzzidiag? Is there a way to check the crank position sensor in Guzzidiag? Thanks