Electrickery issue

So she’s still doing it. She being my 2001 VFR, and it being electrical undercharging.

Having got a new generator on it and a decent reg/rec, I am convinced that its a fault in the loom or another one of the components. So where from now? I will be disassembling the loom connectors, checking for any dirty earths, but what else could it be? It feels like the general running of the bike is draining the power, so the bike isn’t actually being supported by itself and is needing the battery to support it. Putting the lights on makes the battery worse so effectively I only have a daytime running bike. I will be retesting the charging system, but I am pretty convinced that its not on the charging system, but on the usage side. But how to test that?

Basically, I am after a set of tests to see which bit of my bike is not working properly. Any suggestions?


You’ve not said what you’ve done yet (perhaps you did elsewhere), but things to do are:

Check that the stator coils are okay - unplug the connector to the stator (it’s three wires). Check that:

  • Each has no continuity with ground
  • For each pin, the resistance between it and the other two is roughly consistent.

Check that the stator’s producing reasonable voltage and it’s getting through the reg/rec:

Start the engine. Set the voltmeter to high AC and check that each of the three pins from the alternator have around the same voltage. Stop the engine, plug the alternator back into the loom and start the engine again, measure the (DC) voltage across the battery. Leave the engine running until it’s warm, and test the (DC) voltage across the battery again, then the AC voltage between each of the pins on the alternator and ground.

Check there’s no accidental load on the bike when the engine’s off - turn everything off and disconnect a terminal from the battery. Set your multimeter to ~20A and put one lead on the disconnected lead and the other on the now-empty terminal. Keep turning the current down until you see someithing. Hopefully you’ll see nothing.

Follow the cable from the negative terminal of the battery to the frame or engine, check the resistance between the battery terminal and that bit of frame or engine.

Your reg/rec will have three wires going into it from the coils (on the AC side) and either another pair or another three coming out the other (DC) side; does yours have two or three on the DC side?

Faulty battery??

Yeah. that’s a fair point. Remove it from the bike and charge it (externally) one evening and again in the morning and see how far it’s dropped.

Do you eventually appear to run out of electricity (things stop working) or does the battery just go flat?

Battery isn’t the issue. Its a running out of electricity when running rather than bike going flat. I only just got home the other day, but only because I turned all my lights off.

What happened on my ride in was the first 40 miles of motorway were fine. I got to Raynes Park and all looked great. I stuck full beams on, heated grips, indicators and brake lights, and all was good - basic test of what is going on at idle. I have a voltage indicator light on both of my VFRs because of their inherent charging issues.

And then it all went to ****. The voltage continually dropped and dropped and dropped like the bike was unable to support itself at idle for any period of time, like the bike had continually been draining itself at the higher revs of the motorway journey, but not enough to cause problems, and as soon as you got to the stop start of London it all went pear shaped.

If you can get it to me I’ll run some diagnostic tests on it :wink:

its a good day to work on a bike in a nice undercover garage drinking tea and chatting along while its pissing it outside :wink:

i had this exact same problem on my hornet 3 months ago ,wasn’t sure if it was the battery or rectifier had a new rectifier at home ready to fit ,but bike just died in the middle of holburn in rush hour on the day of the tube strike ,luckily their was infinity motorcycles shop right there so i got ripped right of on a cheap no name battery from them and managed to make it home.
i then fitted the rectifier straight away and the bike has been fine.

I am seriously considering taking you up on that. You open saturdays? And how much to diagnose do you think?

Yup Saturday Surgery open every weekend. Half an hour poking it with my multimeter will cost you a packet of biscuits :wink:

What flavour, and when do you open? And I’m happy to do any prep work on it to get panels off etc.

Open from ten every day including Saturday, drop me a text when you’re heading over and I’ll put the kettle on.

Cheers Scorch. I’ve asked for leave to come down on Saturday. The Mrs has provisionally agreed, but depends on how bad a week it is for her. I might swap the Givi wingrack over for the rack on the other one - I’ll be bringing some tools over to very quickly get the rear fairing off whilst the bike is still running and warm because the charging system on these things is notorious for being absolutely fine at cold, but not worth the scrap metal when hot.

Also, just to spice things up, there are some additions to the electrics which I am pretty certain aren’t the cause of the problems - HID light kit, accessory fuse box at the front, heated grips and a modified wiring loom for the reg/rec to plug into so there’s a nice big mainline straight into the battery, not relying solely on the piddly little wires through the loom - a very well recognised mod designed to help things. And a MOSFET reg/rec because the airflow onto the reg/rec is stupidly lacking. I can bring along the standard bulbs as well, but pretty sure its not the lights causing issues.

Sounds as though you’ve done all the right things, perhaps a fresh pair of eyes might spot the problem :slight_smile:

I’ve got to that point too. General mechanics I can do. Electrics I can do up to a pretty high point, but there has to be a point at which I just go ‘wtf’, and need to bite the bullet. I think I might be there. Hopefully Saturday…