Cranks fine cold, acts like flat battery when warm.

My Bandit has developed and issue in the past week. 

8 month old battery,

1st time it had a issue,  spins over fine when cold, after a 10+ km ride to work I get a slow crank then click, click, click
An hour and a half later, fires up fine.

Cold battery has 12.8V, drops to 12.1V cranking, charges at 14.2V

Clean all terminals and all good for about 4 to 5 days of travel, bike sits for 6 days, 4 degree morning, starts fine, same issue hot, click click, click etc
Battery voltage hot, 12.4V, still charging at 14.2V

Next morning, 0.2 degrees, click click, click etc, battery is at 12.2V but drops to 8V under load, I blame the battery, get a new one, spins over fine, go for a 5 km ride and try a restart, slow crank then click, click, click. Still sitting at around 12V when trying to crank.

It has a auxiliary plug to a charger port (must have been a Peter Stevens thing, I haven't sen one on another Bandit from new) and a lighter style accessory plug, I've removed both of them to isolate anything, no change.

Any ideas? 

- Starter relay not coping with warmth?

It could be a starter relay, if you get a click but no load on the battery then that's the problem I was having on the VStrom. I suppose slow cranking could be caused by bad contact/arcing in the starter relay contacts. When it happens, if the relay is easily accessible like it is on the VStrom, you could bridge the starter contacts. Just be warned that I did a fair amount of damage to my long-nose pliers this way.

BTW Since members here had, had good results with knock-off fuel pumps I bought a copy starter relay off EBay. Second or third start stuck in the on-position.  

Luckily, I was still in the shed with all the tools to disconnect the battery. I tried it again with the same result, I'm glad this didn't happen on the side of the road. I've since fitted a second hand genuine unit with better results.

Murphy's Law will tell you that the problem will be in the most inaccessible part of the bike.

Before spending on starter relays etc. I reckon you need to consider a component that is subject to temperature change so my first place I would look is the lug at the crankcase end of the negative cable from the battery. Maybe even the lugs actual crimp onto the cable. This lug is probably more susceptible to corrosion and temperature change than most other points on the start circuit.

You probably need a second person to assist but measuring point to point around the start circuit with a multimeter (while the engine is hot) should reveal a voltage drop. I don't know the exact figure but I reckon the starter motor would probably fail to spin at around 10 volts so a 2 volt drop would be an issue.

Just my thoughts!!

When hot does it crank fine with a different battery? My wifes Jetta battery was only about that age and it totally failed, to the point that a jump start pack couldn't even fire it into life. Luckily 40 month guarantee meant new battery.

reddog wrote:When hot does it crank fine with a different battery? My wifes Jetta battery was only about that age and it totally failed, to the point that a jump start pack couldn't even fire it into life. Luckily 40 month guarantee meant new battery.

Between shift work, a back yard overhaul that I have to have done before my daughter's 21'st and the fact I've got access to our 2nd car for 10 days while my daughter is doing exams I bit the bullet and dropped it off to the dealer, I didn't have time to do it myself and I need it back on the road by Wednesday next week or it'll be a $35x2 taxi ride to and from work each day it's not back on the road.

To answer your question, changing batteries made no difference at all, every time it started it seemed to struggle more and more, even cold it was getting real slow and just starting, all the voltage / charge checks came up ok

It's the starter motor, 2 of the magnets have started to lift off, they haven't quite let go yet, the dealer says they haven't seen one this late build have a magnet issue, they have taken pity and are supplying the starter trade price, if I had time on my side I'd get an aftermarket one. 

On the positive side, I'm just thankful it didn't happen while Baz and I were in Tasmania

All sorted ?

paul wrote:All sorted ?

Yeh, all sorted.

It was well overdue for a major service so between that, gear position switch and the starter motor it was a expensive exercise.

Runs better than a new one ATM.

I've got the old starter and when  time permits I'm going to strip it and make sure the loose magnets aren't cracked, all going well I'll try a reglue for a spare