DIY Tachometer

[mvalenti]

So I was contemplating a DIY tachometer, because I removed mine, and now need one for diagnostics... Talking to an electrical engineer here at work about the circuit I stumbled upon a work around when asking how the circuit worked... I asked why cant I just use my multimeter to read the Hz??? We ran out to the parkinglot to try... took an old lead, stripped of the end, placed it nead plug wire 1 of my jeep and viola. it works... kind of.... need to do some math since Hz is measuring the pulses in seconds and we want minutes.... so multiply by 60... Hope this helps...

[Normk]

Another trick is to measure frequency between two stator legs. I do this frequently to set RPM on generators but works on bikes. One simply needs to consider the stator. Rather than doing the math, one can run the bike in gear and note frequency at a speed for which the RPM is known and then divide.

[Steve]

... I asked why cant I just use my multimeter to read the Hz??? ...

GREAT idea.

Will have to try that when I get home. I think both of my meters will read Hz.

Will also make it MUCH easier to see very small differences when tuning the mixture screws.

.

[mvalenti]

Didn't work so well on my mutimeter, it wasn't shielded as well as the one at work.

[TheCafeKid]

Didn't work so well on my mutimeter, it wasn't shielded as well as the one at work.

Not only that but your jeep doesn't use a wasted spark system like the GS does.
Where your jeeps number one plug only fires when it's time to fire, your number one plug on your GS fires on both the firing stroke and non firing stroke. When it's not firing, the number 4 cylinder is.

[mvalenti]

yep, that too... darn...

I have one of these, http://www.sears.com/shc/s/actron-dw...78S6078486508P and wanted to try to use it but cant figure out to hook it up on a bike.

[surviverguy]

yep, that too... darn...

I have one of these, http://www.sears.com/shc/s/actron-dw...78S6078486508P and wanted to try to use it but cant figure out to hook it up on a bike.

I've had two of those over the years/ a great tool. Try attachimg the leads to the 12 volt coil connections and set the switch to rpm's

[Steve]

Not only that but your jeep doesn't use a wasted spark system like the GS does. ...

Doesn't mean it won't work, only that it will read twice as fast as it should.

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[Dogma]

Doesn't mean it won't work, only that it will read twice as fast as it should.

.

Twice as fast as it should, which is half as fast as actual rpm without wasted spark. So for a GS, multiply Hz by 60 to get rpm. Check?

I really need this to work, since I'm one of those who can't hear the rpm changes when adjusting idle mix.

[mvalenti]

Thanks and much appreciated, Was thinking the same thing, but hoping I wouldnt have to strip the insulation back to expose the bare wire.

[mvalenti]

Twice as fast as it should, which is half as fast as actual rpm without wasted spark. So for a GS, multiply Hz by 60 to get rpm. Check?

I really need this to work, since I'm one of those who can't hear the rpm changes when adjusting idle mix.

WHEW! I thought I was the only one!!!