A couple of things caused the 90's 250/400 greybike Honda's to blow reg/rec's

the o.e. part isn't very good.
lots of UK bikes tend to run H4 bulbs with 55w headlights instead of the 35w Jap o.e. bulbs and run the headlights all the time.

the Tyga tail just exasperates the problem by mounting the reg/rec badly and stopping cool air getting to it..
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