Author Topic: Tach Compatibility  (Read 413 times)

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Offline dubepj

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Tach Compatibility
« on: December 24, 2017, 12:48:15 PM »
I have a 1998 Dyna WideGlide.  These bike don't come with a tach.  Found a used tach off a 1985 FXR.  Do you folks know if this tach will work on my 1998 Dyna??  It has the HI-4E single fire ignition on it.  There is a brown wire that is supposed to connect ot the tach that is currently not used for anything.  Thanks for your replies and everyone out there that rides, Have a Merry Christmas and a Happy New Year.
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Online ecir50

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Re: Tach Compatibility
« Reply #1 on: December 24, 2017, 04:35:26 PM »
Sounds like that would work.

Offline JW113

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Re: Tach Compatibility
« Reply #2 on: December 24, 2017, 05:26:06 PM »
Should work fine, a tach is tach as long as it's made for a 2 cylinder HD.

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Offline Breeze

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Re: Tach Compatibility
« Reply #3 on: December 25, 2017, 05:02:20 AM »
I remember having to change something when I put a single fire ign. on my '92 Dyna. My tach read 1/2 speed as it was designed to read dual fire ignition. All I can clearly remember is "pink" is tach wire.  :scratch:
I'm starting to believe my body is gonna outlast my mind.

Online DresserDan

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Re: Tach Compatibility
« Reply #4 on: December 25, 2017, 07:50:24 AM »
I don't know about the Harley tach. It may be wired for dual fire as it was for a older style. I like and use a Auto Meter for bikes. It is made to run on either dual or single fire. You will have to find a custom made bracket for them but they work good.

Online Reddog74usa

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Re: Tach Compatibility
« Reply #5 on: December 25, 2017, 09:00:37 AM »
The tach will work on your wide glide. Check the crane site or do a search for the installation instructions for that iggy and wire accordingly. Piece of cake
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Offline JW113

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Re: Tach Compatibility
« Reply #6 on: December 25, 2017, 09:38:26 AM »
I remember having to change something when I put a single fire ign. on my '92 Dyna. My tach read 1/2 speed as it was designed to read dual fire ignition. All I can clearly remember is "pink" is tach wire.  :scratch:

An older stock tach is connected to the coil. So it gets a pulse every turn of the crank, and the tach is calibrated to that. If you put an aftermarket single fire coil on, you now have "two" coils. If you connect the tach to just one of them, yes it will read 1/2 of what it should since you only get a pulse ever other spin of the crank. I thought most aftermarket single fire ignition modules have a tach output, which gives one pulse per plug fire, mimicking the stock dual fire. If it does not have this, you would need a diode bridge to connect to both coils to the tach line.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Online Burnout

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Re: Tach Compatibility
« Reply #7 on: December 28, 2017, 06:53:26 AM »
"don't need no stinking tach!"

I know when to shift by when the pushrods start making dents in the top of the tank!   :fish:
They don't call me Ironhead Rick just because I'm "hard headed"

Online Hossamania

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Re: Tach Compatibility
« Reply #8 on: December 28, 2017, 05:37:22 PM »
"don't need no stinking tach!"

I know when to shift by when the pushrods start making dents in the top of the tank!   :fish:

That's about the same technique I use! One day that thing is going to blow shrapnel right through the side of my leg.
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Offline Bruno-Katz Fokkerpilot

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Re: Tach Compatibility
« Reply #9 on: December 31, 2017, 04:55:52 AM »
I had this very problem when i installed a Genuine Harley tach onto my `97 Fatboy which has an Accel single fire ignition. The brown wire off the single fire unit must connected to the tach. My problem was the tach seemed very sluggish on the needle.

It was if the needle refused to go above 3000, even at 85 mph it barely registered 3,100. At a standstill in neutral, i could rev it`s nuts off but tacho wouldn`t rise above 2,700.

So, i installed a tach adaptor but didn`t make any difference at all. As i own a European import bike i`m now led to believe that the gearing is different to US bikes. Maybe this is why i can`t get a true reading. I can live with it as the tickover speed registers true and really that`s all i wanted the tach for in the first place to set the engine speed at idle. Would love to know if our UK gearing is different to mainland USA ?

i`d also like to know if anyone on here has got their genuine Harley tach to register over 4,000 on the road and if so, what speed were you doing ?
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Online Hossamania

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Re: Tach Compatibility
« Reply #10 on: December 31, 2017, 08:24:14 AM »
I think it has something more to do with the single fire ignition verses the dual fire stock ignition.
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Online fbn ent

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Re: Tach Compatibility
« Reply #11 on: December 31, 2017, 08:31:51 AM »
IIRC a Crane single fire has a tach wire that makes it work correctly. Brown I think.
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Offline JW113

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Re: Tach Compatibility
« Reply #12 on: December 31, 2017, 11:22:41 AM »
Most export bikes back in the day were fitted with HDI or Harley-Davidson International gearing, which was a 61 tooth rear pulley. This gave a final drive ratio in 5th gear at 2.92:1. I have this pulley on my softail, which results in a nice round number of 75mph @ 3000rpm.

-JW
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1945 Indian Chief   1978 XL Bobber

Online Hossamania

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Re: Tach Compatibility
« Reply #13 on: December 31, 2017, 11:35:10 AM »
The fact that it is not showing proper rpms in nuetral while revving means that gearing is not the issue.
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Offline 14Frisco

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Re: Tach Compatibility
« Reply #14 on: December 31, 2017, 11:42:59 AM »
Would love to know if our UK gearing is different to mainland USA ?

According to 1997 Softail parts and service manual - no, they (OEM) are/were the same.

Offline Bruno-Katz Fokkerpilot

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Re: Tach Compatibility
« Reply #15 on: January 02, 2018, 04:39:49 AM »
JW and Frisco, that`s interesting, yes my rear pulley is 61 tooth but wondering what the front pulley is ?

Still not really the issue, as i stated previously, my tach (HD Mini ) doesn`t seem to play above 3000 rpm. Also, it seems to take it`s time sorting itself out to what the motor is actually turning in rpm. In effect, it acts very sluggish. Although it`s an electric tach, i was wondering if it has some kind of damping incorporated ?

It`s not a " twitchy " needle, it`s very steady and does not bounce about like some tachs.

I can live with it but just curious as to why it doesn`t exceed 3000 at 85 mph. Of course, i may have the wrong tach for my bike ??
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Online fbn ent

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Re: Tach Compatibility
« Reply #16 on: January 02, 2018, 06:51:21 AM »
A two cylinder tach is a two cylinder tach. It's HD too.......?  :nix:
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Offline Bruno-Katz Fokkerpilot

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Re: Tach Compatibility
« Reply #17 on: January 02, 2018, 07:29:25 AM »
Yes mate, HD Mini tach, it does state on the box that it`s for every make of softail after the year 2000. Mine is a `97 but i can`t see what the difference would be ?
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Offline JW113

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Re: Tach Compatibility
« Reply #18 on: January 02, 2018, 08:06:25 AM »
Hey Bruno, the front should be 32 tooth if it is the stock one.

As already has been said, how the tach functions is independent of the transmission or gearing. I think what you have is a broken tach!

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber