Ignition Coils from Mikes XS

[xszgrider]

I received my new coils from Mikes XS today. I measured the primary resistance with 2 different digital meters and one read 2.4 ohms and the other 2.3 ohms.

The original system including the ballast resistor and tolerances, can very from 2.8 ohms to 3.4 ohms.

This means that an extra 1.5 amps will be going through the TCI unit using the coils from Mikes XS. This is about a 23% increase.

I am concerned about the TCI unit's ability to handle this extra current.

Has anyone actually used these coils without problems?

[Brian_D]

the power input and output from the TCI will not change - its the power to the coils that will be increased to the full 12V during the RUN cycle.

can see the diagram in this thread - the only difference for the 80G is the main switch uses 4 wires instead of 3; however, the additional wire is used in the lighting system and not the circuits shown.

[xszgrider]

Mike's XS Ignition Coils

Thanks for you reply,

I realize that with the ballast resistor removed, there will be 12 volts at the positive terminal of the ignition coils. The original circuit had a total resistance of approximately 3.1 ohms. Mike’s coils have a resistance of 2.4 ohms.

The current that flows through the coils and is switched to ground through a transistor in the TCI unit, is determined by the resistance of the circuit.

The greater the resistance, the lower the current and vice-versa.

Since, Mikes XS coils have a lower resistance, more current will pass through the coils, creating a hotter spark but causing the TCI unit to work a little harder to switch the extra current(amps).

Current in an electric circuit causes the heat. More current, more heat. More heat can lead to failures.

Since the TCI unit is over 27 years, I am concerned about damaging it. Transistors of the 1980’s are not near as efficient as those of today. Since the ballast resistor is technically bypassed during startup, maybe Yamaha designed a higher safety factor into the unit.

I haven’t heard anyone state that are using Mike’s XS ignition on a running bike.

[TopCatGr58]

Hey John,

I've put them on my bike, an 81SH, and Mason in Ca. has put them on his...a 79 IIRC, plus a few others over the last year. So far have not heard of anyone with a failing TCI. Perhaps Randy, our resident electrical GURU can chime in on the robustness of those transistors you mentioned?? He's able to repair the older 2H7 series TCI's with no problem replacing resistors, etc. as needed.

Another alternative may be to tap into a 12 volt line that is NOT routed thru the TCI, but is still switched with the key, the TCI will still be controlling the triggering of the coils thru the gray/orange leads, but the coils can get their juice from a simple line tap, ie. the rear running lights!

Fortunately, the 81 TCI was designed to work without the ballast resistor.

As for the older machines, both the 2H7 TCI's are much more plentiful, but there is also a completely different inexpensive automotive alternative IF the TCI does fry, and you/we are not able to replace the fried transistor.
T.C.

[xszgrider]

Mike's XS Ignition Coils

Top Cat
Thanks for the reply. I saw your post on the installation of the coils, but apparently you had not actually tried them out at that point.

Since several XS1100 owners are using them successfully, that is good enough for me.

Thanks again,

[mason79]

i have an f and bolted right in with no mods , took the resistor out of the loop, i did notice on ebay the stock honda cb750 coils look exactly like the mike's xs', just a thought, mike says they are rated at 35.000 plus volts, that is high output in my opinion,

btw, runs great...

[Pat Kelly]

35,000 volts is double the OEM 15,000 volts.

[pggg]

So I wonder what the story is with my dynacoils, apparently they're 30,000 volts or more, but not being a sparky, doesn't amps make the spark hotter? and they're claimed as performance coils, or is that just because fast bikes/cars use them just to be cool anyway? Volts or amps I don't know, but the dynacoils haven't burnt out my black box.....yet. That automobile ignition setup could come in handy one day

[Pat Kelly]

I have the Dyna coils on my E, 3 years now with no problems. I did notice a difference in my "seat-o-the pants" meter after installing them. Seemed like a bit more "oomph" than before.
I used the Dyna coils (advertised as 45,000 volts) and silicone wires, MSD plug boots, Bosch platinum plugs one heat range cooler.
The bike also has (installed previous to the coils) Jardine spagetti pipes and K&N in the airbox. One size up on the main jets and one notch lower on the needles.

[panshovel]

I put Mikes coils on 78 e runs great.
DO NOT solder the ends to the coil. They tend to loosen up the inside, but they still work