Stumble / Cut Out / Hesitation at Specific RPM

[Cosi]

Good point - that's something I've got in the tool box..

Finally, my first real contribution to the technical section, I must be learning....

 

[Rob]

Tim - 10 pages on and still no cure. Frustrating! 

Checking back, your YouTube clip shows how noticeable and repeatable that misfire is revving at standstill, as well as when riding. 

You say that you had the problem with the original ignition setup as well as after fitting the DMC.  So we are looking for something that wasn't changed when you fitted the DMC.  We've had some diversions along the way with pickups and HT coils and you have subsequently swapped out/bypassed 'everything' - but what about the connector from triggers to old ignition & new DMC?

Worth clocking the crank end as Cosi suggests - did you check the trigger gaps when swapping ignition plates over?

If the above is OK we must surely now be back with something non carb or ignition related.  So - cracked vacuum balance pipes or inlet manifolds? Did the carb swap include the choke plunger assembly?

Not sure if there's an error protection circuit in the DMC, but it would require removing the connector and letting the DMC calm down before I could start it again

Switching the DMC off (ignition or kill switch) and back on will reboot it...useful if the engine backfires when trying to start it.

 

[laverlesmains]

Not sure about loose nut, but I'm sure I've got a couple of screws loose.

All checked out on leads, sparkies etc.  No fuel filters, alternator is ok (and removed from circuit right now)..

With both the original and replacement (from Red) triggers I cleaned up and insulated the fragile wires running from the triggers.

Over the coming days, will:
[list type=decimal]
[*]See if I can get a good scope or meter reading on the pulses from the triggers
[*]Will check the manifolds.
[*]I think I've done it before - but will install a ground wire directly from engine.
[*]Will clock the end of the crankshaft
[/list]

 

[Grant]

I still think it's fuel related.

 

[MotoV]

With both the original and replacement (from Red) triggers I cleaned up and insulated the fragile wires running from the triggers.

Have you check to make sure the triggers are wired correctly? They should spark when a blade is brought towars them vs. pulled away.
Per Piet on another thread

If you swap polarity of the pick-ups they function differently. 

In stock configuration, the pulse is generated when the trigger advances towards the pick-up.  When polarity is reversed, the impulse will occur when the trigger has passed the pick-up.  Easy to check with a slim screwdriver.  Either the spark occurs when the screwdriver hits the pick-up (stock), or when you pull it off the magnets (reversed).