I have an intermittent starting problem: when I press the starter button, the starter motor just keeps churning. Turning the ignition off does not stop it and it keeps going until it runs the battery dead. Having browsed the forum, I am wondering if this could be similar to ScottDT's starter motor problem, but here's the full description:

Latest example was yesterday. The bike started and rode fine (around a mile). After a brief stop, she restarted normally. A couple of miles later, after another brief stop the problem was back, stranding me at the roadside. After intervention by a couple of lovely local residents with a battery charger, the bike (irritatingly) started immediately and perfectly and I rode her home.

This issue comes completely out of the blue and only happens very occasionally, which makes it very hard to know whether any "fix" has actually sorted it. And it means I can't trust the bike.

My observations:

1/ The handlebar switch itself seems fine - it's springy and firm and pops back out as normal.

2/ I already replaced the starter relay a few months back.

3/ This problem only seems to happen when the bike is warm, never when starting her from cold.

4/ It is months between occurrences (previous was September last year).

5/ On this occasion, the battery seemed low ( I had recently finished fixing a wiring issue with lots of indicator testing) but on previous occasions it has been high, so that in itself doesn't seem to be the cause. I was, however, surprised that the battery was so low after several miles of ride - would this not be enough to recharge it?

6/ Because it is so long between occurrences I can't remember if on some occasions the bike has actually started but the churning continues, but my gut is saying Yes.

I would really appreciate any thoughts on this. Is it likely to be the starter clutch as in Scott DT's thread? Anything else I should check? Many thanks in advance.

Lo

Edited Saturday at 10:573 days by Lolorides
Making the model of bike clear.

First off, what bike (it might help people)?

It might be useful to pull the starter motor out of its hole and (carefully) test it. You might feel or see what's going on. It could be a bit sticky or something, or feel rough...

Sorry, it's the same bike - Yamaha SR125 - which seems to go from one problem to the next, to the next...

I've been doing a lot of online research meanwhile, and seen a theory about the starter relay. Which is: If the battery is low a big(ger) charge is needed to kick the starter over, creating sparks and a "micro-weld" between the plates in the relay when the bike is started hot, keeping the switch open and preventing the ignition switch having any effect. However when the bike cools, the contact breaks returning the starter operation to normal.

That explanation fits well with the behaviour I'm seeing (especially as battery was low on this occasion) but does it sound correct or just like nonsense?

Although I initially said it had happened when the battery was high, I've also been reading that during urban riding the bike probably doesn't get enough sustained revs to recharge the battery, so it could be lower than I think. It only does urban trips, mainly short.

Any and all ideas on the likelihood of the "micro-weld" scenario or suggestions as to what the problem could be are gratefully received.

Lo

Not a clue about that micro-weld theory, but as for the low rev charging... Yes, that's possible. I know that some vehicles don't charge much when it's sat idling.
The issue with urban riding is when people are used to cars. In a car, you get to the highest gear you can (before it strains) as quickly as you can to save fuel.
But with a bike, it's more about staying in the lowest gear (without revving the nuts off it) that you can to sustain manoeuvrability...
I work on this theory... If the speed limit is 30mph, I don't go past 3rd, 40: 4th, 50: 5th & so on... Like this, you still have the response to accelerate quickly to avoid dangers.
It does keep your revs a little higher and probably burns a little more fuel, but let's face it, it's not like continuously doing 40 in 2nd in your car..! lol