Surging and bucking is banished!

thanks to Pete Roper and MG Cycle the new phase sensor is installed and life has returned.

The new sensor does not say  Magnetti Marelli but it did have a white label with “V11” which I took as a good sign.

I tipped up the front of the tank to fish the cable in and out but not a difficult fix. Old part pictured below.


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Good-o! They're a weird thing. Some seemingly last forever, some seem to fail randomly. Heat has a lot to do with it in fact I'm not entirely sure heat related failure isn't a deliberate fail-safe to save the engine in extremis but I have no written evidence to suggest that.

A spare one is something I'm thinking it might be wise for me to start carrying if I head off on a long trip out in urine drinking territory on the GRiSO Turismo. It's not like they are bulky or take up a lot of space! Both my Grisos are getting fairly long in the tooth, although Red Bike it's more years than miles. If anything is going to go wrong with them it'll probably be electrical.

Oh, and your sort of intermittent failure is pretty uncommon. Usually they work or they don't. Bucking and surging as the sensor cuts in and out is rare. Usually you just get a sudden shut down or a non start event, usually when hot. Simplest way to diagnose is to pull a plug cap and stick a plug in it and rest it on the head and hit the button. No spark? Most likely the phase sensor.

glad you figured it out!

I had to ask Pete as my traditional method of diagnosis failed me.[You must be registered and logged in to see this image.]