The standard, seperate regulator and rectifier units on the later model Royal Enfield Bullet are not noted for their reliability. Aftermarket replacements are available but can be expensive.
This instructable will show you how to fit one of the widely available, more reliable and less expensive integrated regulator rectifier units off a modern Japanese motorcycle in place of the standard unit.
Step 1: Can I do this to my bike?
This guide only covers Indian made 350cc and 500cc Royal Enfield Bullets fitted with the 12 volt AC/DC charging system. Given it's long production run, there are a large number of variants of these models. It is not suitable for all of them.
A few checks will tell you if this modification is suitable for your bike. You need to be able to answer YES to the following questions:
Do you have a 12 Volt battery? This modification is NOT suitable for 6 Volt systems.
Does the engine need to be running to turn the main headlight on? If you can turn the main headlight on when the engine is off, you have a different charging system and should proceed no further.
Are there four wires leading from the alternator? Follow the bundle of wires emerging from the top of the primary chaincase (see red arrow on picture). It should contain a total of four wires. Any more or less and you should stop here.