revtothelimit - motorbike forum

I did 80+ miles out with the classic yobs on Sunday and the bike ran faultlessly. It was properly caned on the way home too! When I hooked it up to the optimate that evening,I notice it took over an hour to present the fully charged green light,usually the green light is on in about ten minutes.
Yesterday when I started the bike,it was only showing a max of 10.4 volts regardless of revs. Effectively not charging.

Now begins a series of testing electrical components,stator,rotor,regulator,rectifier,blah,blah. Man I hate footering about with electrics.

The like was for the ride and canning, not the leccy fault. That sounds like a pain.

Supermofo wrote: Tue May 26, 2026 9:45 am The like was for the ride and canning, not the leccy fault. That sounds like a pain.

All part of the 'oul bike' experience.I don't mind when I have a definite plan of action,but with electrical faults I'm thrashing around hoping I happen upon something to fix.

Yup, she's older than me! And I'm fucked.

I quite like elctrics (obviously not imtermittemt faults). It can be much easier than deciding whether a mechanical component is worn out or just has racing clearances!

If it’s a permanent magnet alternator, a first test might be a headlight bulb across its output leads.

Skub wrote: Tue May 26, 2026 10:09 am

Supermofo wrote: Tue May 26, 2026 9:45 am The like was for the ride and canning, not the leccy fault. That sounds like a pain.

All part of the 'oul bike' experience.I don't mind when I have a definite plan of action,but with electrical faults I'm thrashing around hoping I happen upon something to fix.

That's the definition of fixing electrics.

Stator,rotor,voltage regulator and rectifier all tested as per manual and found to be within spec. So,according to my reading of the magic meter everything is working fine and I should have 14 volts when the engine is revved.

The only problem is...I still get only 12 odd volts when blipping to 5k.

My tenuous grasp of sparkery tells me,since there is good output from the stator,then the voltage regulator maybe isn't allowing enough juice to the battery.
It's a mechanical regulator,so can be easily removed from it's case for examination. I fired up the bike with the reg casing off to see if there was any action between the little coil and the bi-metal contact. All looked good visually and I cleaned the contacts anyway,but not being entirely certain of what I should be seeing,it was all a bit inconclusive.
Eventually I bit the bullet and ordered a Mosfet solid state regulator. Plugged it in,fired up the bike and fuck my old boots I have a good 14 volts on the blip.
As an aside,during the testing process I had difficulty with my digital meter when the engine was running. There's no spark plug resistors,no suppressors and the old Mitsubishi cdi is mega electrically noisy. The digital display just fed me random,scolling numbers. Impossible to get an accurate reading.
I had a cheap analogue meter lying about,but it was cheap for a reason. It was shite. I bagged an old (1963) Avometer 8 mark 2 off the bay for not much money. It isn't a pocket model.....

That Avometer brings back some memories - right back to the Physics lab at school! A nice thing to have in your kit.

Nice avo !

Is that bakelite, cool!

KungFooBob wrote: Mon Jun 08, 2026 6:39 pm Is that bakelite, cool!

Apparently so.

Been after one for ages, just can't find the right one.

ZRX61 wrote: Mon Jun 08, 2026 9:34 pm Been after one for ages, just can't find the right one.

There are a few on the bay in the UK for not much money. I likely got lucky,as mine works great and I even managed to source a 15volt battery needed for the ohms option. Some of those battery sellers are asking more than the cost of the Avo.

Skub wrote: Wed Jun 10, 2026 9:41 am

ZRX61 wrote: Mon Jun 08, 2026 9:34 pm Been after one for ages, just can't find the right one.

There are a few on the bay in the UK for not much money. I likely got lucky,as mine works great and I even managed to source a 15volt battery needed for the ohms option. Some of those battery sellers are asking more than the cost of the Avo.

AVO's are $150-$200 here, not sure about the batteries.

ZRX61 wrote: Wed Jun 10, 2026 3:18 pm AVO's are $150-$200 here, not sure about the batteries.

I paid 30 quid inc P&P. Places like Glanford electronics are looking £12 + £11 postage for a BLR121 15v battery. You'll get one on the bay for £6 or so.