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Tech Corner: Alternator Tips

Tech Tips

Iron Barrel Alternators

There are basically three alternators that were used in the Iron Barrels. From 1995 until mid 1999 they were affectionalty known as the “3 wire” alternator. It ran the entire bike from headlight to taillight. It had a two piece rectifier and regulator. It was also marginal in terms of being able to keep up with the needs of the bike. This was because all US bikes are wired with the headlight on all the time. This alternator was never intended for this type of load. It had a smaller 7 amp hour battery. The three wires of the alternator were reduced to two wires as they went to the regulator/rectifier. Alternators produced AC current and the rectifier turns it into DC. Two wires in, two wires out. The regulator’s job is to regulate the voltage so that it only charges when needed and does not overcharge the battery. These early units were plagued by weak rectifiers.

In mid 1999 the AC/DC system was introduced. This was a four wire alternator which produced more power. The alternator was split in half electrically with two of the wires providing power only to the headlight and the other two powering the bike through the regulator/rectifier. It has plenty of power to keep the lights and the bike running full time.The headlight could care less if you are pushing AC or DC through it. The headlight circuit has it’s own small voltage regulator under the seat – it looks like a flasher).  The regulator/rectifier units were upgraded from the earlier ones and rarely fail.

When the Electric starter was introduced in 2002 an even more powerful unit was required. Enter the third and final 4 wire alternator. This alternator was used with a 14 amp hour battery right up until the final production of the Iron Barrel. This unit is the “hot” setup for all Bullets. You can use them with any Bullet even the three wire units. The trick is to make sure you also get the upgraded regulator/rectifier that is matched to this alternator.

Changing an alternator and regulator/rectifier units is an easy and straightforward job. The only thing to remember is to make sure that when you tighten the stator coils up that you make sure there is at least 0.006 thousands of an inch between the rotor and stator all of the way around. It is also good practice to change the rotor with the stator as they do lose their magnetism over time.

Lean Burn Alternator

The Lean Burn uses a more powerful alternator of a different design than the old Lucas types that are found in the iron barrels. It also carries the ignition triggering unit as part of the assembly. There isn’t much to know about them and they rarely fail.

UCE Alternator

The UCE alternator is similar to the Lean-Burn with some important exceptions. It has a series of magnets around it’s circumference that tell the EFI system where the crankshaft is, what it’s rpm is and whether or not it is accelerating or decelerating. The EFI system then adjusts the timing, fuel flow etc to meet those conditions.

Enfield in Twighlight