Solve your battery charging woes – fast!
Does your battery keep draining? It’s time to find the fault, and fix it
Test the voltage
If your bike has a charging issue there are two common culprits: a faulty rectifier or blown stator. Using a multimeter set in the 20V (volt) range, check the battery voltage with the engine running. Typically with 3000rpm on the tacho the voltage at the battery terminals should be over 13 volts; a faulty charging system will be showing lower than 12.6 volts.
Check the resistance
Unplug the reg/rec from the main loom and test its resistance using the multimeter – the specific values will be in your bike’s workshop manual. Bridge the probes between the pins in the connector one at a time, looking for the values of each. A healthy resistance reading will fall between the upper and lower values stated in the manual.
Recce the reg/rec
Locate your bike’s regulator/rectifier, undo the connectors that clip into it and inspect the condition of the contacts – they need to be clean and free from corrosion and show no evidence of overheating. If it looks like it has been getting hot then there is a chance that there may be too many accessories running at the same time.
The real deal
Buying a genuine replacement reg/rec ensures there won’t be a problem with compatibility. Pattern options can be cheaper but it’s often a bit of a lottery with regard to fitment and they can cause further damage if they’re not the correct spec. If you decide to use a pattern part, get advice from your local dealer as to what they can supply or recommend.
Replace and refit
Before you install the new regulator make sure it is the same size and type as the old one. Remove the body of the reg/rec from its mounting point on the bike, often they are simply retained by two 6mm bolts. Refit the unit and clip together the connector. Repeat the running voltage test from step one.
Access the stator
To reach the stator you will need to remove the cover that it sits behind. Undo all of the bolts and make sure you have a tray underneath to catch oil. The cover will have a bit of resistance as you try to pull it off because of the magnetism on the rotor. As you remove it make sure any location dowels have remained in place and not fallen into the tray.
Don’t blow a gasket
Fit the new stator and, as specified by the workshop manual, install the bolts to the correct torque. Refit the cover using a new gasket; always place the gasket onto the crankcases first, slipping it over the dowels and using a dab of grease on other areas to prevent it flopping over. Fit the cover and tighten all the bolts lightly first then torque up to spec with a wrench.
The state of the stator
If your rectifier checked out OK, assuming the wiring is in good condition you need to check the stator. The typical layout of a threephase stator/alternator uses a three-pin plug with wires of the same colour. Measure the voltage at idle speed – it should be around 25 volts for each phase.
Any obvious damage?
Check the condition of the old stator as sometimes there is a visible indication of damage, such as burned out coils. Undo the bolts that retain the stator and then give the cover a thorough clean inside and out. Then take time to clean off the old gasket material from the cover and crankcases using a plastic scraper or other suitable tool.
Tighten up and test
Once you have the cover fitted, don’t bolt the panels back on just yet. Do another voltage check with the engine running as in step one. With the new stator fitted there should now be the correct voltage reading of over 13 volts. Warm the bike up and check that the stator engine cover is oil tight, then replace any body panels.