This is a mod I've done on a few bikes now and replaces the standard OEM thyristor based shunt regulator rectifier with a newer technology MOSFET shunt regulator rectifier.
Why upgrade
The OEM thyristor based units can get extremely hot and have a shorter lifetime as a result commonly failing in a couple of ways.
The first failure mode causes them to undercharge and, over time, this causes the battery to fail due to it being insufficiently charged long term.
The second failure mode causes them to stop shunting the excess current and the charging voltage goes through the roof. This can start to pop bulbs, kill instruments and has been known to cause ECU failure (although I haven't heard of that happening on a KTM).
A major advantage of the MOSFET unit is the stability of the charging voltage. Even at tickover with lights on and fan running, you'll still see somewhere between 13.8 and 14 volts. Just above tickover the voltage rises to somewhere in the region 14.3 volts and stays rock steady throughout the rev range.
So, upgrade if yours fails or if you want something more reliable than standard with a more stable voltage. Granted, a MOSFET unit isn't guaranteed to stay working but the failure rates seem tiny. I've only heard of two failed units. One was supplied from a breaker in a non-working condition so history unknown. The other was killed by someone connecting the +ve and -ve the wrong way round. They don't like that.
Why the Shindengen FH008
This will fit in the standard location and can be wired in salvaging the original connectors off the old regulator rectifier. A used unit can be found from a UK breaker for £60 to £80 delivered and all you need to do is chop the wires off the old unit and solder them onto the new one.
You can upgrade to waterproof connectors if you wish and if your connectors are completely corroded then you may need to but if everything is in serviceable condition and cleans up well, it's an easy upgrade.
Upgrading the regulator rectifier on my bike
My 990 had a Motobatt fitted by the previous owner around 14 months and not many miles ago. It was sluggish on the starter and the Optimate would always charge it at full rate even straight after a decent ride. Hooking up the multimeter showed why:
Checking the charging system showed it was struggling to get above 13.2 volts at best and the voltage was actually dropping off with increasing revs occasionally dropping below 13v.
So, I ordered one of these from a breaker:
Next, I removed the OEM regulator rectifer. I cut the leads off it and removed the connectors from the connector blocks. I cut the connectors off the FH008 ending up with this:
I ended up completely replacing the +ve and -ve wires and their connectors as the wires were corroded inside and the connectors had seen better days. The alternator wires and OEM 3-way connector were fine and these were just soldered on to give the same length as the OEM unit. All joints were covered with glue-lined heat shrink tubing. You should use glue-lined for covering the solder joints to keep the water out.
This is what I ended up with:
...and that just bolts on perfectly where the old one was without fouling the bash plate unlike the bigger MOSFET units:
As the saying goes, "the proof of the pudding is in the eating". Firing up the bike with the meter probes on the battery gave this rather better reading:
My work here is done.
Why upgrade
The OEM thyristor based units can get extremely hot and have a shorter lifetime as a result commonly failing in a couple of ways.
The first failure mode causes them to undercharge and, over time, this causes the battery to fail due to it being insufficiently charged long term.
The second failure mode causes them to stop shunting the excess current and the charging voltage goes through the roof. This can start to pop bulbs, kill instruments and has been known to cause ECU failure (although I haven't heard of that happening on a KTM).
A major advantage of the MOSFET unit is the stability of the charging voltage. Even at tickover with lights on and fan running, you'll still see somewhere between 13.8 and 14 volts. Just above tickover the voltage rises to somewhere in the region 14.3 volts and stays rock steady throughout the rev range.
So, upgrade if yours fails or if you want something more reliable than standard with a more stable voltage. Granted, a MOSFET unit isn't guaranteed to stay working but the failure rates seem tiny. I've only heard of two failed units. One was supplied from a breaker in a non-working condition so history unknown. The other was killed by someone connecting the +ve and -ve the wrong way round. They don't like that.
Why the Shindengen FH008
This will fit in the standard location and can be wired in salvaging the original connectors off the old regulator rectifier. A used unit can be found from a UK breaker for £60 to £80 delivered and all you need to do is chop the wires off the old unit and solder them onto the new one.
You can upgrade to waterproof connectors if you wish and if your connectors are completely corroded then you may need to but if everything is in serviceable condition and cleans up well, it's an easy upgrade.
Upgrading the regulator rectifier on my bike
My 990 had a Motobatt fitted by the previous owner around 14 months and not many miles ago. It was sluggish on the starter and the Optimate would always charge it at full rate even straight after a decent ride. Hooking up the multimeter showed why:
Checking the charging system showed it was struggling to get above 13.2 volts at best and the voltage was actually dropping off with increasing revs occasionally dropping below 13v.
So, I ordered one of these from a breaker:
Next, I removed the OEM regulator rectifer. I cut the leads off it and removed the connectors from the connector blocks. I cut the connectors off the FH008 ending up with this:
I ended up completely replacing the +ve and -ve wires and their connectors as the wires were corroded inside and the connectors had seen better days. The alternator wires and OEM 3-way connector were fine and these were just soldered on to give the same length as the OEM unit. All joints were covered with glue-lined heat shrink tubing. You should use glue-lined for covering the solder joints to keep the water out.
This is what I ended up with:
...and that just bolts on perfectly where the old one was without fouling the bash plate unlike the bigger MOSFET units:
As the saying goes, "the proof of the pudding is in the eating". Firing up the bike with the meter probes on the battery gave this rather better reading:
My work here is done.