Replacement TCI Transistors

The original transistors used in our Transistor Controlled Ignition igniter boxes are Fuji made ETD41-035. They were discontinued many years ago.

ETD41-035 transistor

Various sources dedicated to old Yamaha motorcycles such as the Vision and the Virago suggest that the MJE5742 is a drop-in replacement.


TCI Repair

For many years my Police Special had a very nasty habit of dying like I had hit the kill switch.
It never sputtered first and would almost always do it within the first 1 km from my home.

Charging System

Circuit diagram

A. C. Generator

1. Checking method

a.    Connect D. C. voltmeter to the battery terminals.

b.    Start the engine.

Lighting System

Circuit diagram

Lighting system tests and checks

Sensors and Switches

Fuel sender unit

1. Inspection

a.    Remove the sender unit from the fuel tank.

b.    Use a pocket tester (with ohm x 10 scale) for this check. Connect the pocket tester leads across the green lead and the black lead of the sender unit. The meter should show the following resistance at the specified fuel level. If not replace the sender unit.

Wiring Diagram



Ignition System

Circuit diagram


Electric Starting System

Circuit diagram

Starter motor

1.      Removal

See Engine Dissassembly, Starter and Generator.

Electrical Components




Signal System

SIGNAL SYSTEM Circuit diagram

Signal system tests and checks