Advise needed: Electrical Faults with CBR125

I seem to have an Intermittant fault when starting, sometimes you press the starter switch but bike will not turn over, after a couple of trys there will be no response from the switch and the netual and head lights will go out showing that there is no power. Once it’s bumped / jumped and sitting at high revs for a while it is fine, turning off and starts 1st time even leaving over night and starts fine.

This has happened 3 times over 4 months (weekend rider) and it is after the bike has been used for a few hours. Checked the battery and volt meter and they seem to be fine.

Anyone got any other ideas what could be causing this and any tips for bumping a bike on your own?

Thanks in advance.


Check the battery terminals are on properly and tight. Otherwise - If the bike is charging correctly but the bike is sometimes not starting and then losing power to the headlights it is almost certainly the battery. It is very difficult to test a battery other than by putting it under load and seeing how it behavies. Yours is behaving like it is not holding charge properly and is often the first sign of faliure.

spray some wd into the control, or open it up and just clean connectors up et, also see if plugged into loom ok and spray wd in the connector too.
gets sh1tted up/wet etc this weather
just check all conections nr battery, solenoid etc etc, lol

:frowning: to hear that this happened after we all went seperate ways on sunday …you have got my number now so if you get stuck again give us a call

As said possible battery is loosing its ability to hold a sufficent charge and listening to yours starting at Newlands it did seem to have a hesitant moment which is either battery ( seems that a few cbr’s have similar issues ) or the starter motor is needing a clean and draining the battery quickly

Does the bike start if jump leads are used if it fails to start as normal ?

or possible ideas to check first

main cable connector/main fuse ( possible located on the starter solenoid ) has a loose terminal that when cold makes a sufficent contact but after a while when used it expands slightly with the heat etc and then this creates the problem of no power . if happens again and possible to do so try this … make sure bike is out of gear and bridge the two solenoid terminals with a jump lead ( or normall used is a screwdriver or spanner ) to see if the battery will operate the starter itself and turn the bikes engine over ( if so you know that the problem lies with the electrics ) if it doesnt turn over then i would suspect the battery … this can be pinpointed by attaching a seperate charged battery using jump leads and trying again using similar method and if it works now then no power is coming from your battery …

if still no work then its a cable/starter issue

Cannot see it being Kill switch or starter switch as this would not cut all power and in reality if ignition switch was playing up it would be a bit more hit a bump or play with keys etc it would falter

Ideas for bumping

Try and use natural landscape features ( hills and even drop kerb sections ) o your advantage

Make sure the area you are trying to start in is safe enough ( not high traffic) and a good surface ( not gravel/loose )

If possible turn the lights off

make sure choke is on if it is needed before you start running

start in 2nd or 3rd gear and get as much speed up as you can before you release the clutch ( put it in gear and hold clutch in before you start running/being pushed )


you can make a small set of jump leads that will allow you to get a jump start …and do not take up a lot of room to carry with you

If battery is not accessible get a lead made up with a connecter similar to an optimate connecter fitted and attact it to the bike and battery in an accessible spot and then another cable( at least a metre and a half in length ) made up with the connecting connector and two crocodile clips ( i used to use a system similar to this using 16Amp cable and thsi succesfully started either my zzr600 and various other large capacity bikes as well as smaller cc ) that allows you to connect to a suitable battery ( car/other bike etc) ( or if battery is easy to get to then just attach crocodile clips to both ends )and as the cable is small it is possible to coil it up and store it in small spaces on the bike ( under seat etc )

if jumpstarting make sure that if from a car then the car is not running when doing this

do not allow the vehicles to touch as this will result in lots of sparks and risk of damge to paintwork etc as it will cause the bodywork to act as the earth cable

if using the above cables do not operate the starter for prolonged periods ( maximum 5/6 seconds ) as they are not designed to take that much and will overheat if used for too long but they are handy for emergencies etc ) but in reality you should not operate the starter for any long period of time anyway

also if a connecter like optimate etc is fitted means you can connect a battery charger over night easier etc

Thanks for all the help guys a few things to try out. Which leads to another question head lights only have a button for high beam no switch to turn main lights off, has anyone tried to wire in a switch before? Have checked a few other bikes for the same model and year and they are the same.

Thanks again.