Hi everyone,

So I just bought this K100RS1 and everything is going smoothly but for the battery that has issues for the first 4-5 minutes of driving.

The bike start easily but if I let it idle for too long, the battery indicator lights up and the bike will power off. Same for when I am riding, if I arrive at a red light, the bike would switch off while I activate the clutch. I need then to restart it, it works but it is not very convenient.

I bought a new battery, that I charged fully with a charger and the issue was solved for 2 days. Then, it started doing it again. As soon as the bike as been riding for 4 or 5 minutes, all is good, the idle is good, no more battery light on the dashboard.

Did anyone experienced the same issue or has any advices to give? It is something that drains the battery while the bike is parked?
Thank you for your help !
Léo

The only thing lurking is the clock, but with a good battery it takes more than 4 weeks to notice the voltage going down.
When bike is running, at 1500RPM, the voltage on the battery should be around 14.4V.
If less than 14, time for a new regulator.

Is the bike stock?  Or have there been modifications done to the motorcycle, such as cafe-ing it, adding aftermarket electronics, etc.?

Does the headlight come on when you turn the ignition key to start position and turn off when cranking the engine?

Hi Leo,
Do you mean the engine is stalling when you stop at traffic lights when the engine is still cold, but the problem doesn't occur when the engine is warm?
What RPM does the engine idle at when cold?
Richard.

As Arlina says the clock is always on, but it is digital and should not really pose a problem. There isn't an anti theft system fitted?. I would use a battery tender, Ctek make some good kit, it will give you more life from your battery.
Cheers
Mike

What about the spark plugs and HT wires? Poor sparks might explain your problem when engine is cold.

Which type of spark plugs do you use? Resistive or not resistive? (with a R in the code?).

How old the HT wires?

I would be inclined to fit an AMP METER in order to have a LIVE reading of this problem.You can then 
have a true indication of whats happening,or if you have a spare alternator fit it and see if this works 
better.

Those symptoms sound like a dirty starter, perhaps you don't know but the starter is used as a pathway for the motor when not doing start duties. Engine issues just like you describe are mentioned in here many times in the past. Clean the commutator and brushes and you may find it fixed. If you start in on it replace the earth strap to the gearbox with a larger one also for good measure. Just the things done in the past.

moriarti wrote:I would be inclined to fit an AMP METER in order to have a LIVE reading of this problem.You can then 
have a true indication of whats happening, or if you have a spare alternator fit it and see if this works 
better.

That won't help to solve the problem.  Leakage currents that cause battery drain are measured in milliamperes and a normal ammeter measures amps.  It won't be sensitive enough.  Furthermore, you'd have to fit any current measuring device in the path of the leakage and he doesn't know where that leakage is occurring; so how does he know where to place the meter?  

If the OP wants to track down a leakage, he'll have to do the following:
1. Remove all of the fuses from the fuse block and any auxillary fuses that may be part of aftermarket equipment installed on the motorcycle.  Set the ignition off and remove the ignition key.

2.Insert a multimeter in series with the ground lead of the motorcycle.  Put the multimeter in current reading mode and on a sensitive scale like 200mA.

WARNING:  At no time should you try and start the motorcycle, or turn on any circuit on the motorcycle.  You will destroy your multimeter.

3. read the residual current being drawn from the battery.  Is should only amount to 20mA or so as this is the current that is drawn by the clock.  If the reading is higher than this, the problem is a leak somewhere in the non-switched circuitry of the motorcycle

4. if the reading is OK, insert one fuse at a time and measure the current.  if it suddenly jumps, the cause of the leakage is in that circuitry downstream of the fuse that just got inserted.

ABS if fitted can come up with faults that drain the battery. It took me a long time to find the problem because as soon as I disconnected the battery to check for parasitic current the fault went away until the ABS was reset.

OP's k100 is an 1983 vintage. No ABS installed.

Thank you guys for all your answers, I've had no time to ride the bike lately but will be back at it. I've orderned a new fuel filter to instal as well, I've read on the forum that could be the issue. The bike was running around 800rpm at idle when cold but then as the bike would warm up, the issue would disapear and it will run on a normal idle speed.

I guess that I've been in the wrong direction with the battery.

Thank again for the help, it is much appreciated !

Bike should run at 950/1000 idle warm.