wiring in a tach?

[fastpakr]

Good point, I did double those numbers...

I thought you were saying that you could plug an auto tach into the neg terminal on one gs coil and get a correct reading with it on the 8 cyl mode? I was suggesting you would be 4x too high, which seems to be confirmed by that last post of meter results. I'm confused. 8O

[Anonymous]

Here is the result of my Dwell/Tach test on my GS1100.

Meter connected to the White wire of the 1-4 coil.

Engine idling at 1000 rpm indicated on mechanical tach

On 8 cyl scale = 250 rpm

On 4 cyl scale = 500 rpm

On 2 cyl scale = 1000 rpm

These readings are from an analog meter and are approximate, but in the ballpark.

The 4 cyl GS engine has 1 pulse per rpm. So you need a tach with a 2 cylinder setting.

I was quite surprised at the results. I have tried to work it out in my head and always came up with 2 pulses per rpm

Most of the inexpensive Tach's I have seen only have 8-6-4 cylinder settings.

You get one pulse per revolution. Remember we are dealing with a 4 stroke. Each cylinder fires every 2 revolutions. Thanks for the measurements, this is what I was saying.

If an automibile has 8 cylinders and one coil it fires 8 times for every two revolutions of the crank. A 4 cylinder car fires the coil (single coil) 4 times for every 2 revolutions. The GS fires each coil 2 times for every 2 revolutions or 1/2 the count for a 4 cylinder tach wired to the coil. You then get 1/2 the RPM reading on the tach.

[Anonymous]

Good point, I did double those numbers...

I thought you were saying that you could plug an auto tach into the neg terminal on one gs coil and get a correct reading with it on the 8 cyl mode? I was suggesting you would be 4x too high, which seems to be confirmed by that last post of meter results. I'm confused. 8O

In an earlier post I did. I was using the Big N Dafts pickup coil data. His tach is reading 2x what it should. At the time I assumed we were discussing his situation. I was probably wrong on that one also. A 4 cylinder car tach would probably work for him. It's a moot point, since I don't think he is using a car tach.

Too many tach and pickup coil combinations here!

[fastpakr]

Ah, now it's all becoming much less mirky! Thanks for clarifying.

[gtsg01]

I did a quick search for Tach Adapters. Autometer makes a model 9117 that splices into the positive wire and senses the current fluctuations and converts them to a tach output.

On our bikes, both coils are powered from the same wire (orange/white) so if you put the 9117 into the circuit before the splice, the adapter would sense both coils, giving a combined 2 pulses per rpm.

http://www.egauges.com/pdf/AutoMeter/561.pdf

that would allow a readily available 4 cylinder tach to be used. The 9117 is listed between $68.00 and $78.00 on the web.

[Anonymous]

I did a quick search for Tach Adapters. Autometer makes a model 9117 that splices into the positive wire and senses the current fluctuations and converts them to a tach output.

On our bikes, both coils are powered from the same wire (orange/white) so if you put the 9117 into the circuit before the splice, the adapter would sense both coils, giving a combined 2 pulses per rpm.

http://www.egauges.com/pdf/AutoMeter/561.pdf

that would allow a readily available 4 cylinder tach to be used. The 9117 is listed between $68.00 and $78.00 on the web.

Glad to have you posting.

This is interesting. I've not seen this before. If it does what it says it should do the trick. The problem with using an auto tach is that they aren't weatherproof. Does anyone have a solution for that?

[Anonymous]

Ah, now it's all becoming much less mirky! Thanks for clarifying.

I just looked back at the sequence of posts and I was wrong. Later on Big N Daft asked a question. This is all too confusing for me.

[Anonymous]

Ah, now it's all becoming much less mirky! Thanks for clarifying.

I just looked back at the sequence of posts and I was wrong. Later on Big N Daft asked a question. This is all too confusing for me.

Thats why they call me Big N Daft!

[redliner1973]

On our bikes, both coils are powered from the same wire (orange/white) so if you put the 9117 into the circuit before the splice, the adapter would sense both coils, giving a combined 2 pulses per rpm.

correct me if I am wrong, but does the orange and white wire supply the 12volts B+, NOT the impulses? if so, how could this thingy 'sense' 2 coils?

[Anonymous]

On our bikes, both coils are powered from the same wire (orange/white) so if you put the 9117 into the circuit before the splice, the adapter would sense both coils, giving a combined 2 pulses per rpm.

correct me if I am wrong, but does the orange and white wire supply the 12volts B+, NOT the impulses? if so, how could this thingy 'sense' 2 coils?

Yes, the orange and white wire is the battery.

It senses 2 coils by monitering the current in the wire. Notice that the way they have the coils wired in the example circuits. All of the coils are fed by one battery wire. The module is in series with it and can then detect any current fluctuations in ALL of the coils.

In order for this to work for you, you need the same configuration. You cannot have 2 separate wires delivering power to the coils since there is no way to monitor them both. Simply rewire the battery to the coils.

[gtsg01]

The Orange/White wire is spliit somewhere beteen the Run/Stop and the coils. I have never taken the harness apart, but my guess is that the splice is close to the coils.

It would probably be better to run a new wire for this task, just to be safe.

[Anonymous]

The Orange/White wire is spliit somewhere beteen the Run/Stop and the coils. I have never taken the harness apart, but my guess is that the splice is close to the coils.

It would probably be better to run a new wire for this task, just to be safe.

Exactly. Both coils must be fed from the same wire that is connected to the monitor. There isn't any electrical reason to run 2 wires anyway. It might have been easier to manufacture with a splice where they put it. Who knows for sure?

[Detman101]

Here is the result of my Dwell/Tach test on my GS1100.

Meter connected to the White wire of the 1-4 coil.

Engine idling at 1000 rpm indicated on mechanical tach

On 8 cyl scale = 250 rpm

On 4 cyl scale = 500 rpm

On 2 cyl scale = 1000 rpm

These readings are from an analog meter and are approximate, but in the ballpark.

The 4 cyl GS engine has 1 pulse per rpm. So you need a tach with a 2 cylinder setting.

I was quite surprised at the results. I have tried to work it out in my head and always came up with 2 pulses per rpm

Most of the inexpensive Tach's I have seen only have 8-6-4 cylinder settings.

So a 2-stroke tach would work?

Dm of confused...

[Anonymous]

Here is the result of my Dwell/Tach test on my GS1100.

Meter connected to the White wire of the 1-4 coil.

Engine idling at 1000 rpm indicated on mechanical tach

On 8 cyl scale = 250 rpm

On 4 cyl scale = 500 rpm

On 2 cyl scale = 1000 rpm

These readings are from an analog meter and are approximate, but in the ballpark.

The 4 cyl GS engine has 1 pulse per rpm. So you need a tach with a 2 cylinder setting.

I was quite surprised at the results. I have tried to work it out in my head and always came up with 2 pulses per rpm

Most of the inexpensive Tach's I have seen only have 8-6-4 cylinder settings.

So a 2-stroke tach would work?

Dm of confused...

You need a tach that reads 1 pulse on every revolution of the crank. That would be one from a single cyliner 2-stroke engine. There are lots of dirt bikes, but not many have tachs. Let us know if you find one.

[Anonymous]

Very good people...Since our bikes spark each cylinder at top dead center (combustion stroke or not) its 1 pulse per stroke.

On a four cylinder GS and a two cylinder GS there wouldnt be a difference, they both have two coils and both have 1 or 2 pistons at the opposite spot of the other.

So if you connected a 2-stroke tach to a 4- cylinders one coil it would read accurate same as if you connected a 2-stroke tach to one of the twins coils. twin is the same as a four, just two more pistons.

The reason why a cars tach wont work is because it fires the cylinders when they need it so it would appear our engines are running much faster then they really are.