Found smoking gun

[gordonr]

My shop installed a audio system on an 11' recently. System included Biketronics 2 ch amp, Sony MEX-M70BT and customer supplied Hertz front speaks. Anyway the system developed a pop on initial start. He brought the bike back complaining it was really loud on start and thought it would ruin the speakers. I personally looked at it and found some small issues with grounds and corrected them. Also corrected a voltage drop to the main battery input to the head unit also. Did find the battery test bad with only 200cca avail. So the battery was changed out and checked out at 439cca. System still popped on initial start. Located issue was coming from head unit but as a result of what happening with the starter. Heres a scope shot of what I discovered.





Left side shows voltage, right side shows starter current draw. 50ms time scale

[UltraNutZ]

good detective work there gordonr.   


That is one helluva spike in current draw from hitting that start button for what appears to be about 8ms @ 600+a 

[speedzter]

You could use a relay with a delay (small capacitor on the coil ) on the supply feed, so it disconnects when the starter is activated, and has a short delay before restoring power to the HU.

[gordonr]

You could use a relay with a delay (small capacitor on the coil ) on the supply feed, so it disconnects when the starter is activated, and has a short delay before restoring power to the HU.

We tossed that idea around but this guy has some routine before he starts his bike. Could be 15 sec to a 30 the with ignition on before he starts it. He comes in today for a discussion to see what he wants to do. Current on starter settles out to 130 and the solenoid peaks at 30 then settles to 14. I cant say how much life is left in this starter or even if its going to get worse.

[speedzter]

I was thinking you would use the N/C contacts and only energize the relay with the starter.
It's not fixing any starter issue, but it should alleviate the HU spiking/popping.

[gordonr]

I was thinking you would use the N/C contacts and only energize the relay with the starter.
It's not fixing any starter issue, but it should alleviate the HU spiking/popping.

Is your idea to use pin 87a on the start relay (if it has one?). Thats not a bad idea.

[ncpowell]

Amp has built in delay to prevent this...with ignition on for substantial time before it's gonna be an issue.  Could install inline switch on amp relay wire and flip the switch after the bike is started.

[speedzter]

Is your idea to use pin 87a on the start relay (if it has one?). Thats not a bad idea.

That was the idea, but i would probably use a separate relay.
I would say the factory starter relay should have the 87a pin, but may not have a terminal fitted to the relay base.
Just check the current rating of the N/C contacts if using a micro relay.
https://www.denniskirk.com/drag-specialties/micro-starter-relay.ph20880.prd/H20880.sku

[gordonr]

Thanks for the input. The customer said he would live with it. It's funny he wasn't even interested in any tech talk and thanked us and left. He's taking a trip so when he gets back I hope I can have some time with it to R&D a start inhibit radio bypass circuit.

[FSG]

to R&D a start inhibit radio bypass circuit.

in a similar way some disable the headlight during starting