Just thought I would post this as an example of an intermittent fault that becomes worse as the components warm up, typical of HT coils, regulators and ignition source coils.

The first trace in blue shows the output from a regulator that was suspect. In this case the fan would run but not as fast as it should, and once the bike got hot may not run at all or need a flick of the finger to start it. As you can see the pulses above the line are irregular. The spikes below the line are typical of partial diode failure.

From this one trace it is not 100% certain regulator is at fault, could be a loose wire or faulty ACG coil.

Now a second channel (red trace) is connected to the ACG output.

As can be seen the out put is good and regular but as the regulator has warmed up it is less frequently converting the ACG output into DC (pulsed) to drive the fan.

A check such as the above with an oscilloscope on all a motorcycles electrics could be very worthwhile before events such as the Scott or SSDT.

regulator fault.doc

You will have to view the attachment in Word at 200% to see it properly

Edited January 9, 201511 yr by dadof2

I have an 07 Gas Gas and have had 3 Ducati regulator/rectifiers fail. Once no spark, twice no fan and each time there was a burn mark on the epoxy showing that some component (diode?) burned out.

The box is mounted above the radiator and my theory is as it heats up the fan power output decreases making the bike run hotter eventually making the regulator/rectifier fail.

I moved the box to behind the number plate and so far no problems. A quick test would be to look and feel how fast your fan is running. If it is slow, you could be prone to failure.

On a side note, I am still using my Ducati box with no fan power. I'm running the fan off of 10 nimh AA batteries running through a motor speed controller, voltage meter as well as using stock thermostat. I have to swap batteries once during a regular riding session. Also for amusement and curiosity, I put a meat thermometer in a gap between the radiator and shroud.

It could be a bad earth or contact causing the problems.

You could fit the Leonelli regulator and rectifier from the later gas gas or sherco.

With a bit of searching you could pick up a bridge rectifier and 12v regulator from an electronics store that will do the same job and cost peanuts.

I have done this before on an early Gas Gas and it works, It's simple to do also.

Search the forum as I think I posted about this last year.