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 | Friday, August 14, 2026 |
Testing the Ignition System for Problems
This was originally written for Norton Commandos using the Tri-Spark Ignition System. I have re-written it to cover:
- Norton Commandos with a dual-fire 12 volt coil or two Lucas-type 6 volt coils.
- Triumph and BSA Twins with points off the end of the exhaust camshaft (Tri-Spark models (Tri-0005A, Tri-005B, and the current Tri-0006) with a dual-fire 12 volt coil or two Lucas-type 6 volt coils.
- Triumph and BSA Singles with points in the timing cover (Tri-Spark models Tri-0005A, Tri-005B, and the current Tri-0006) with a Lucas-type 12 volt coil.
- Any other bike where the current Tri-0006 ignition can be installed.
- If you have issues with a Triumph Trident or BSA Rocket three and the Tri-0002, that is not covered here but call or write me.
The Tri-Spark ignition system is OK for single coils from 3.0 to 5.0 ohms or two 6-volt coils connected in series that stay within that range. Below 3.0 and the Tri-Spark output transistor will be destroyed, over 5.0 it will become intermittent. When I use a dual-fire coil, I use the Drag Specialties 4 Ohm Mini Dual Fire Ignition Coil - 2102-0276. Be careful they have a lot of different identical looking coils and only the 4 phm version is acceptable and the 0.4 ohm version will instantly destroy a Tri-Spark ignition! One place to get them is https://www.denniskirk.com. In the instructions below I talk about the positive and negative terminal on the coils - the Dual Fire coils usually do not have the markings so don't worry about that for them.
These bikes came from the factory with positive ground - if you decided to change that then you need to translate everything below that talks about polarity!
There is a rampant urban legend that the Tri-Spark unit gets too hot under the points cover - that might have been true with the initial versions but has not been true as long as I've used/sold them which started in Jan 2017. The two I've had returned since then that the owner insisted had heat problems are running fine in other bikes - one 1967 Triumph 650 and one 1974 Norton Command.
If you have problems that you think are the ignition system, do these tests, in order, carefully and accurately:
- Disconnect the two wires at the Tri-Spark.
- Measure and record the voltage across the battery.
- Put your Red meter lead on one of the head fins.
- Put your Black meter lead on the Black/Yellow wire leaving the points area.
- Turn the ignition switch one click clockwise and measure the voltage. If not identical to the voltage across the battery, stop, find that problem and fix. Possible culprits are the fuse holder, master switch and wiring.
- Turn the ignition off and set your meter to the lowest ohms reading.
- Leave the Red meter lead connected to the head fin.
- Connect the Black meter lead to the Black/White wire leaving the points area. You must read between 3.0 and 5.0 ohms. The correct reading is 3.2 to 3.6 but if you're sure your meter is correct 4.4 will be OK. BTW, if you have Fluke meter that does not show exactly zero with the leads connected together, then your leads, lead connections, or Fluke calibration is wrong. Search for "Having your Fluke meter recalibrated" - the explanation is excellent. Fluke meters are quality, but they DO NOT remain calibrated - they are a compilation of electronic components who all change over time. I never use one for anything like automotive work - that is not what they are designed for! For ohms readings you are MUCH better off with a cheap meter with a rx1 scale, a mirror behind the needle, and zeroing the meter before EVERY reading.
- If you've passed all the tests above as well as the two Tri-Spark tests in the manual, I would be shocked if there was an ignition problem, but there are more things you can check that are ignition related:
- If your voltage regulator is Podtronics, it must be replaced. I recommend the Tri-Spark VR0030 (MOSFET Regulator) or even the stock Bridge and Zener.
- Look at your coil primary connections. The Black/White wire must be connected to one of the two coils minus connection. That coil's positive connection must go to the other coil's minus connection, and that coil's positive connection must go to a Red wire from the harness.
- Pull off the coil spark plug wires and measure from the coil positive connection to the coil spark plug wire connection. I don't remember the exact resistance, but it is around 12k ohms. Whatever it is, the two coils must be very close to identical.
- Measure from the coil's positive connection to the case of the coil - it must be infinite.
- Measure from the coil's spark plug lead connection to the case of the coil - it must be infinite.
- Measure end to end of the spark plug wires with them both disconnected - they must read zero.
- Remove the spark plugs and measure from the spark plug wire connection to the center electrode - it must be close to 5k ohms.
- Measure from the spark plug wire connection to the body of the plug - it must read infinity.
- If you are not using standard resistor plugs of the correct type - bad idea!
If that all passes, quit thinking about ignition!
BTW:
- I would start with overheated gas in the bowls for a problem that happens when hot.
- Failing that then you may be running too lean when the problem shows.
- For hard starting when hot, you are probably doing in wrong. If the engine has been stopped for a short time (under 5 minutes, then just kick. If longer, then a tickle is probably required. If that doesn't work then you are probably flooded so open the throttle 1/4-1/2 turn and kick.
- For Norton, I use the 1/4" heat insulators between the head and manifolds - I have no idea why Norton chose thin except for Combat engines where they specified thick - AMAL recommends thick.
- For Norton, If you ride under 3000 rpm - stop it! Nortons do not like that. If you want to tool around at 1500-2500 RPM, buy a Triumph - they will do it all day, a Norton will fail you!
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