Have  a look at this maveform from the same MV Agusta F3-800 as the sample in my other post.

This one was taken during cranking.

Let me know if you can work out from the waveform what we identified it to be.

We already suspected the fault but this waveform kinda just put the last nail in the coffin for the diagnosis.

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Looks like to me you have a lower amplitude in the circled area.  Is this problem repeating at the same point or is it intermittent?  Need more info.  Any chance to make the picture bigger Olly?  Thanks.  How many channels is this scope?

Hi it happens the majority of the time only, under cranking not always at the same point of the crank position. It wont start when the fault occurs but occasionally will start.

Its normally accompanied by a loud cracking sound that sounds metallic.

Compressions and leakdwon check OK

The scope is 2 channel but only lets me record one. First fail ::)

This is the only way to get the image off the scope sorry i haven't even re sized them to put them up here.

OK So Busjockey is right it has low amplitude at the point where the fault exists as circled in the waveform.

We suspect the fault to be a slipping starter clutch which intermittantly allows or doesnt allow the bike to start. Its always compantied with a sharp metalic sound when we suspect the clutch re engages after having slipped for a duration.

A Phase sensor fault is also displayed in severe cases, as the ECU uses the MAP sensor to identify stroke and cycle. WIth the low/ inconsistant cranking it appears as though the signal is outside of what the computer is expecting.

Sorry dont have a smaple of the map sensor waveform but may get cance to capture one before the i fit the new parts to put up as referance.

IMO the crank sensor output is still working, just that the engine just rotated slower at that point

autosparky wrote on Jun 14^th, 2014 at 10:00pm:

IMO the crank sensor output is still working, just that the engine just rotated slower at that point

This is pretty much what we suspect. At certain points the one way bearing/clutch that transmits the power from the starter motor to the crank slips and doesnt provide any or adequate drive to the crank.

Given that the engine uses a singular MAP sensor on #1cyl to identify engine phase if the slippage occurs and engine rotation is slow there is either low or no MAP signal generated for the engine to establish phasing of crank and cam and therefore wont start?

Works in theory, well in my head anyway.

We have waited 6 weeks for parts from italy to fix this and they turned up late last week, i have 90% fitted them today so tomorow should be the difinitive fix or not for this scenario.

Will post findings here when i finish the job tomorow.

damn! it never occurred to me to ask if you could do a starter current with a crank sensor.

Maybe this would prove starter current rotation slippage?

autosparky wrote on Jun 20^th, 2014 at 1:03am:

damn! it never occurred to me to ask if you could do a starter current with a crank sensor. Maybe this would prove starter current rotation slippage?

Now thats an idea, wish i had thought of it before the new parts were fitted.

New parts went in this week and no more fault. The after scope results i have left at work so will sift through them and see if there are any of note worth posting and will put them up later if so.

Customer commented the bike had never started so well since he had owned it (from new), so happy to say fault fixed.