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Greetings!

Just finishing a bobber build with my 1994 R100 RT, which includes an Acewell 4553 speedo/tach combo gauge.

The engine won't start, fuel is ok, but no spark.

I'm in the process of learning the ignition system from top to bottom, and hoping that someone has had experience with a similar setup who can help me sort out what's wrong quickly.

I have power on the switched 12v+ on the Green/Blue wire to the left-side coil terminal, and have also patched the Green/Blue switched 12v+ from the original instrument cluster connector to the Acewell switched power supply. Power to the Acewell speedo is good.

There are no volts at the right side coil low-voltage Black wires when they're disconnected, but have 12v+ across both terminals on the coil when the switched Green/Blue wires are plugged in. Measuring the voltage while cranking the engine, there is no interruption to the primary coils on either low-voltage terminal, so there is a constant 12v+ when the engine is turning, suggesting that there's an issue with the trigger/timing system or wiring.

During the build I didn't have the front cover off, so I'm not suspecting any physical damage up there. I didn't add any other electrical components other than LED turn signals and a flasher relay to make them work properly. I did remove the evaporative emission system and the 2 corresponding solenoids, as well as the grip heat. Connectors for those have been isolated.

The tach impulse input to the Acewell is the solid back wire from the original instrument cluster, which as far as I can tell is the same as the second side of the coil low-volt terminal.

Not sure if the updated wiring is incorrect for the timing/ignition system, or if a system component was damaged during the build. Bike ran great prior to teardown.

Any advice is appreciated!

Stock ignition and coil?

Try disconnecting the tach, preferably at the coil.

Thanks for the suggestion. I did disconnect the tach line to the speedo, but not at the coil. Will give it a shot.

Stock ignition system as far as I can tell.

Take the plugs out and rest them against the head. Disconnect the black wires from the coil. use a length of wire to momentarily short the right terminal to ground, you should get a spark. If not replace the coil.

If you do get the spark, disconnect the Acewell wires from the coil but leave the wire from the loom connected. spin the engine.

Spark... there is a problem with the Acewell unit or wiring. Don't know the 'Acewell' setup so I can'r comment further.

No spark... there is a problem with the presumably stock ignition. Go to the three terminal connector uder the front cover and disconnect it and use a jumper to momentarily short the centre wire on the plug to ground several times in quick succession. You should see a spark at the plugs with each touch except the first.

Spark... the problem is likely to be with the hall effect switch in the 'bean can' or the wiring to it.

No spark... the problem will be with the ignition control unit.

If the ICU is faulty, don't reconnect the Acewell until you've checked the wiring and the function of the unit. If either is defective and causing a direct short from battery voltage to the output of the ICU, there's a good chance that reconnecting it will just destroy the replacement ICU.

Rob

Really appreciate the advice Rob.

Tested today with step one of your suggestions by grounding the primary coil manually, and I'm getting a high voltage spark at the point where that terminal is being grounded. Thinking that there's a short between the primary and secondary coils internally. Will be replacing the coil as soon as I can find one.

Update after further testing, 0 ohms across the 12v+ and trigger coil terminals, no reading/infinite across both the 12v+ and trigger terminals to the high volt terminals.

Yes, it very much sounds as though the coil has failed. A replacement coil is the only way forward... but... just a word of advice. When you connect the replacement coil be careful and be ready to switch off quickly. It's not unknown for a faulty ECU to actually cause coil failure.

My advice, assuming your meter has a 10 or 20 amp range, would be to connect it in series with the ECU before you switch on. Assuming a stock ECU (or one of the functionally identical alternatives), when power is switched on, you may get a reading of around 3 to 5 amps for 1 to 2 seconds followed by a fall to a very low reading as the ECU goes in to protection mode (i.e. switches itself of to protect the power transistor and the coil) or you may just get the lower reading (dependant on the position of the sensor in the bean can. If you get a higher reading or the high reading doesn't drop, switch off the ignition ASAP.

Rob

Thanks again Rob!

Will definitely check the ICU output before I put everything back together and attempt to start it.



CC