It Could be Your Battery

Hi All.

In recent weeks my SV650 K3 S has been running pretty rough. I thought it might be the leads/coils breaking down. Anyway the battery gave up the ghost the week before last. £49 for a Bosch battery from Halfrauds which I didn't think was too bad. Since then the bike has been running a lot smoother.

I put this down to low battery voltage from the old battery. My guess is that the small coils on bikes need a decent battery voltage to produce a high enough plug voltage, especially in cold weather.

Tim.

[Sid Squid]

Agree essentially, any coil under voltage will produce poor sparks, but it goes deeper than that I think; all FI stuff runs less well with low system voltage. Of course the charging system should keep the voltage up to acceptable levels, but it doesn't always work out like that.

[ophic]

Gf's GZ125 barely runs at all with a flat battery - weird cos its about the simplest engine you can imagine.

Originally Posted by Sid Squid

Agree essentially, any coil under voltage will produce poor sparks, but it goes deeper than that I think; all FI stuff runs less well with low system voltage. Of course the charging system should keep the voltage up to acceptable levels, but it doesn't always work out like that.

I agree but I'm also begining to suspect more and more that many of the issues you see on FI bikes/cars aren't down to components failing. There is a lot associated with poor earthing and the modern electonics are suseptable (sp) to slight changes from the design specification

[embee]

Going back a few years, in early days of fuel injection on cars, it was quite common to get all sorts of running problems when the battery was on its last legs. This was down to rather primitive voltage compensation characteristics in the ECU (e.g. injector on-time is increased slightly when voltage is low to compensate for slower opening times, similarly ignition coil charge cycle).

A very common problem was after-start stalling. A tired battery would drop volts during cranking and then not recover very quickly, and as soon as the cranking enrichment ramped off after a few seconds the voltage compensation was insufficient and it went lean and stalled. A new battery often cured the problem.

Although we've moved on a lot with car electronics, bikes are still pretty primitive so may well suffer from some of these issues.

Many years ago, car ignition coils were changed to work at 10 volts instead of 12. The feed wire was fitted with a resistor to cut the voltage during normal running but was bypassed during starting. This was in the days before electronic ignition. Shows how old I'm getting!

I remember asking any mechanic of the day: What was the primary function of the condenser in the ignition system that bridges the contact breakers in the distributor. Every single person got the answer wrong.

Most people today would say: What are contact breakers?

I got a new battery a month or so ago after my dad tested mine (because i was having problems with the heated grips) and it had a low efficiency. Since getting a new one, it starts really well in the cold weather, heated grips work, lights dont flicker or anything like that at idle (least, not as much).

[yorkie_chris]

Originally Posted by I'm_a_Newbie

I remember asking any mechanic of the day: What was the primary function of the condenser in the ignition system that bridges the contact breakers in the distributor. Every single person got the answer wrong.

Go on then?

[Biker Biggles]

Is it to gather together the bits of leccy and condense them into one big naff off bit of leccy to make a big spark?

Its a condensor, makes all that vapourous electricity into liquid electricity which you can then collect. I assume is pure electricity thats been distilled off from crude electricity?