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Baron Custom Handlebar-mount TACHOMETER Install
I’ve researched tachometers for the M109R, and concluded that the Baron Custom Accessories tachometer is the most practical.
While there are some cool looking tachs out there, such as AutoMeter and ProCycle, some are not suitable for outside weather conditions, and often don’t include a gauge cup (enclosure), nor convenient handlebar mounting. Vendors try to defer handlebar mounting configurations to 3rd parties, which makes it either hard to find, or very expensive. In addition, some tachs are meant for automotive applications only, and don't support connection to engines with 2 cylinders.
For the M109R, I found that the Baron tachometers are probably as close to ready-to-mount as you can get, plus they’re one of the most reasonable. By the time you've bought another tach, and sourced a separate guage cup and appropriate mount, it's usually more expensive.
A benefit of a handlebar-mounted tach is that you can wire it up to the bike without having to disconnect, or tamper with the M109’s Stock LCD tachometer -- and more importantly, the engine status lights and indicators. The Baron tach can work in conjuction with the existing LCD tach. You’d be able to transfer the Baron tach to another bike later, and not have to ‘restore’ the M109R original LCD tach wiring.
The stock handlebar on the M109R has an average diameter of 1.25 inches (1-1/4”) starting at the center risers, and moving outwards towards the bar ends. As the handlebar gets close to the the handgrips, it tapers down to 1” diameter.
So if you order a Baron tach for the M109R, the 1.25” diameter handlebar mount is ideal.
A Baron tachometer with 1.25” mount and ‘Black’ dial face is Part Number BA-7577U, and sells for about $190
A Baron tachometer with 1.25” mount and ‘White’ dial face is Part Number BA-7571U, and sells for about $220
Typically, when you buy a tachometer to use on a motorcycle, you might be asked to specify if you want one for a ‘Dual-Fire’ ignition system, or a ‘Single-Fire’ ignition system.
In a Dual-Fire ignition system, the coil generates a high voltage electrical pulse to the spark plugs on every revolution of the engine crankshaft – once during the Compression stroke, and once during the Exhaust stroke.
For proper combustion, the spark plug needs to fire during the Compression stroke*, but in order to simplify circuitry, motorcycles with Dual-Fire ignitions have the spark plugs fire on the Exhaust stroke as well. Since there's no real benefit in trying to ignite spent exhaust gases, the second spark is effectively ‘wasted’.
A Dual-Fire Coil is recognized by having two spark plug leads. Older Harley’s, for example, use this type. It’s a single coil unit with two spark plug leads: one lead goes to the front cylinder, and the other lead goes to the rear cylinder.
Single-Fire ignition systems are a little more sophisticated, and were designed to improve on the ‘wasted-spark' method. In a Single-Fire ignition system, the coil generates a high-voltage electrical pulse to the spark plugs only when the piston nears the top of the cylinder on the Combustion stroke. That means it fires after every second revolution of the engine crankshaft.
A Single-Fire Coil is identified by having only one spark plug lead. This is the type that the M109R uses.
Actually, the M109R has two coils, which are mounted underneath the front end of the gas tank, and just above the radiator. One coil has a spark plug lead that goes to the front cylinder. The other coil has a spark plug lead that goes to the rear cylinder.
(To access the coils, you need to remove the side covers, gas tank, and front fairings)
Off the shelf, the Baron tachometer, like many other brands, are configured for ‘Dual-Fire’ ignition systems.
If you try to hook it up ‘as is’ to a Single-Fire ignition system, then the tachometer will only receive half the number of number of trigger pulses that it expects. You’d end up having the tachometer display engine rpm’s at 1/2 of the actual value. (For example, if your engine was running at 4,000 rpm, the tach would only display 2,000 rpm).
There’s a workaround to the problem though.
You can purchase a 'Wiring Adapter’. The adapter takes the pulses generated by both coils, and combines them onto a single Y-shaped wire to the tachometer. This tricks the tach into thinking that it’s connected to a Dual-Fire ignition system.
The Single-Fire Wiring Adapter (Part Number BA-7315-50) sells for an additional $30.
For anyone that works with electronics, the adapter is really just some wire with connectors, and a couple of Diodes and Resistors. There’s an excellent website that explains how to make your own Wiring Adapter, if you’re so inclined.
If so, you can make one for about $5.00
On the M109R, besides the spark plug lead, each coil has two electrical connections: a Positive terminal, and a Negative terminal.
The Positive terminals on both coils use a 'common' wire color (Orange w/White Stripe), whereas the Negative terminals on both coils have unique / independent colors (NEG coil wire for Front cylinder is Green, NEG coil wire for Rear cylinder is Yellow).
The Baron tach has 4 wires sticking out of it:
- The Green wire connects to the Negative terminals of both coils on the M109R, via the Y-shaped Single-Fire Wiring Adapter.
- The Black wire connects to Chassis Ground.
- The Red wire connects to the Positive terminal of one coil (or any other ‘switched’ 12V source).
- The Blue wire connects to the Positive terminal of the other coil (or any other ‘switched’ 12V source).
(The reason there are two Positive wires, is that one 12V wire supplies power to the tach gauge, and the other 12V wire supplies power for the light inside the tach)
Some common complaints about the Baron tach is that the needle ‘jumps around a little bit’, and that condensation sometimes forms on the inside of the gauge glass, but that goes away after a few days of warm weather.
Otherwise, the chrome finish is excellent, and the tach is both attractive, and reliable.
Last edited by asviewedfrommars; 05-19-2012 at 03:02 AM.
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You may want to add a link showing a Baron tachometer.