Electrical

[racer48j]

I have a question about the hookup of the green wire on the tachometer on a Legends car.  With both the ProForm tach that was in the car when I bought it (used) and the replacement ProForm tach (purchased in the off season) I am only able to get the thing to read 1/2 the actual RPM.  (i.e. If the engine is turning 10,000 RPM my tach reads 5,000)  I currently have the green wire hooked to the orange wire coming from the coil closest to the front of the car.  I have tried different combinations of connecting or not connecting the wires on the tach that normally set it for 4/6/8 cylinder operation.  No Luck!
Should I be connected to one of the terminals on the black box, the other coil?  Any help on this would be most appreciated.

[Tom Cole]

I don't know exactly the answer to your question, but I may be able to give you some insight.   I have a Digatron digital tach that I use on my son's kart.  It uses an induction lead that clamps to the plug wire.  The kart ignition fires on EVERY rotation because it has a magneto style ignition.  I wanted to learn a little more about the Legends ignition and get a more accurate RPM reading so I installed it in the Legends car. (By the way, that is not INEX Legal, so it is only used during practice) I put the tach lead on cylinder #1's plug wire and it gave me correct RPM readings without reprogramming the tach.  That means that each spark plug on the legends car is firing on every rotation, just like the kart engine.

So if your tach has a single cylinder engine setting, maybe give that a try?  Like I said, I don't know, but it may be something to consider.

[racer48j]

Thank you for that info.  Maybe I will try contacting ProForm (tach manufacturer) and see if they have any suggestions for a situation like that.

[racer2146]

On autometer brand tachs they have wire loops that get cut to determine the number of cyls on the engine it is reading.  On the back of an autometer tach where  the wires come out there are tiny loops of wire that go out maybe 1/4" then go right back in.  When one of these loops is cut it can be used for a 6cyl engine, when the other is cut, a 4cyl engine.  I don't know what a profor tach is but maybe they use similar wiring so the tach is rather universal to be used with 8, 6 and 4 cyl engines.

[racer48j]

ProForm tach has the same two wires that can be cut or not depending on the number of cylinders.  I have tried all the different combinations in an effort to get the tach to read correctly.  I have posed the question at the ProForm website technical feedback section but so far they have not answered.  I have seen adapters available for the AutoMeter and a few other brands that would leave me to believe something along that line might be required.  When and if I find a solution I will post it here.  Thanks for the feedback.

[elimn8u_43]

The Green wire from your tach will need to connect to your ignition box. On my car using a black box there is a seperate green wire that breaks from the harness this is the one to connect to. Also make sure that the tach is setup for 4 cylinder operation. Hope this helps.

Geoff

[racer48j]

Just curious, is the green wire from your tach making a connection at the black box on one of the wires leading to the coils?  If so, that is the way we have been hooked up since I got the car.
 I couldn't get a response from ProForm on my question about possible fixes.  I don't think I will be buying any more tachs from them.   In reality I probably don't need to worry about a tach much anyway.  With the black box you kind of have a built in governor because they only let you run up to about 10,400 to 10,500 before the ignition starts to flutter.  At least it works that way on ours.

[elimn8u_43]

No, it is not connected to the wires that go to the coils. There is a seperate wire from the box that is a tach output signal wire. I will have a look and see if I can determin what color and pin it is at the box.

Geoff

[DARK AGE 53]

 I have a Digatron digital tach that I use on my son's kart.  It uses an induction lead that clamps to the plug wire. 

Tom, Can you give me a link to this type of tach.

Thanks,
Al

[Tom Cole]

www.digatronusa.com

ARC Racing sells them

[racer48j]

That would be great Geoff, thank you.

[elimn8u_43]

I have 2 cars and both are wired different. One car uses the 600 wiring harness for the black box and the tach wire connects to the black wire on the rear coil. On the other car it uses the factroy harness for the motorcycle and it has an extra wire which goes to the tach. Looking at the plug from the side where the wires go into the connector the colours are as follows ->   Green                        Black (to tach green wire)
                                                      White/Red             White/Green  (both these wires go to the pickup)
                                                       Green                       Red
                                                        Yellow                     Black

Hope that this helps.

Geoff

[racer48j]

Thanks for the info Geoff.  We appreciate the help.

[BATZ]

My tach is also reading half the rpms...I have an autometer, and it is connected to the factory wire harness.(green wire)  I was reading the post above...is the extra black wire in addition to the green?  And if so, where does that extra wire come from?

[knuclebuster]

Hey Batz,
  I also have an Autometer tach that only reads 1/2 rpms.  I am 99.9% positive that I have mine installed and wired correctly.  I called Autometer and they told me that I would have to send it in to have it recalibrated to be used with the Yamaha motorcycle engine.  My tach was manufactured for an automobile not motorcycle, so the pulse count is not correct no matter how you wire it up or clip the two loops.  Call Autometer, tell them the tach # you have and they will tell you whether you will have to have it recalibrated.

This may not be the case with yours, but this is what I found with my Autometer tach.

KB