I wish to replace the coil on my newly rebuilt ES2. The coil that came with the bike is a Bosch TJ12/1, O22, 0222003091 6.
The ES2 should have a 6V system, but has been fitted with 12 v battery and bulbs and doesn't show a charge until high revs. I think the alternator is 6v and only just puts any charge into the battery at high revs with all lights off. It has a very healthy spark.
Does anyone know if the coil with the above identification is intended for 6v or 12 v?
The Bosch website doesn't have this information.
Hopefully Al Osborne will…
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Poor Charge/output 6V/12V
Correction yet again-there is no such thing as a 6V Lucas alternator, a 3 wire alternator (NOT 3 PHASE) can be 12V or 6V. The traditional 6V machines using Lucas 3 wire alternators relied on the switching (PRS8) of the alternator output to (try to) maintain the battery charge ie they increased the alternator output when the head light was on. On converting to 12V one changed battery and bulbs and ignition coil (if relevant) and increased the alternator output by using the Hi output on a permanent basis. THEN to STOP overcharging you fitted a Zener diode. (A Zener diode does NOT give you 12V)
As DC says perhaps you have a smaller rotor? Have you checked the alternator for output and shorting to earth? Have you checked the wiring of your lighting switch? Have you checked the rectifier? Also as DC says why change the coil if you have a good spark BUT if it was a 6V coil then perhaps that would be why you have a good spark-using it on 12V! If the coil gets very warm then it could be 6V then change it, if not go with it, but again you have plenty to check out before blaming the 6V/12V option. Do you have a Zener diode?
I think Richard will be busy at the week end!
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Hopefully Al Osborne will pop up soon. But why change the coil if the spark is good?
The alternator should be OK for 12v. Do you know what size rotor is it? One possible reason for poor charging is if the incorrect small rotor is set inside the standard size stator, giving too much clearance.