Electrical and Tach HELP!

[Bubber]

First let me say that I am electrically challenged ( boy that was kind!).

 

I saw a cheap tach at Harbor freight in their flyer (part # 98480) and I took a chance and bought it.

 

I have attached the instructions and I have many questions that the paperwork did not answer.

 

1) Will it work on the Venture even if only as a tool for syncing the carbs.

 

2) Do you think it is a double pulse or a single pulse. (what do I need?)

 

3) If it is a single pulse can something be put in line to make it work.

I have seen where Harleys require a electronic gizmo to put in line to make some tachs works

 

4) It can be used on a 4, 6, or 8 cylinder. Could I trick it and set it on 8 instead of 4 ????

 

Any help from you electronic Gurus would be a great help.

 

Oh Ya.... What the heck is an "electronic signal point" as stated in the NOTE ?

Remember I am electronically challenged to say the least.

 

Tell me what else I should know about this before I hurt myself.... PLEASE

 

 

Steve

aka Bubber

[MiCarl]

The "electronic signal point" is a place on the ignition module that is provided to connect a tachometer. I do not know if the module has one.

 

Here's how that tach works though - it essentially "counts" the coil firing then divides by the cylinder switch setting to get the RPM.

 

So, lets look at a 4 cylinder distributer automobile ignition:

 

The coil fires for each cylinder every other revolution. Since there are 4 cylinders that means it fires twice per revolution. So, on the 4 cylinder setting the tach will divide by 2 to count revs.

 

Your Venture does not have a distributor ignition, it has a coil for each cylinder. Each coil fires once per revolution (1 firing is wasted). So if you hook the tach to one coil and set it on 4 cylinder (lowest setting) it will count 1 firing per revolution and divide by 2. In other words it'll show you half the actual RPM.

 

To get it to read properly you'll need to hook it to 2 coils. Problem is if you just hook it up because both coils will be firing twice per rev, once at the wrong time, and the current draw will be too high which could damage the control module. You need to put a couple diodes in to isolate the triggers for the coils and still let the tach see them.

 

Probably not a "beginner" job.