Author Topic: Speedo Problems  (Read 2124 times)

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Offline 50Panhead

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Speedo Problems
« on: Wednesday, May 13, 2009. 09:52:27 AM. »
I' bringing this from the Evo Board to the General Board to see in anyone here has any better idea.

I’m still having problems with the Speedo on a 1995  Dyna Convertible reading 20 to 25 MPH fast.
I have a 1997 FXD that I removed the speedometer sender unite from the transmission and temporary installed on the 95 Dyna Convertible. That gave the same results Speedo reading faster.  I had a Speedo Part Number 71014-95 off a FXDL that I picked up from a swap meet and installed it, same thing readings 20 mph fast. I have checked the wiring its all according to the manual. I have checked the battery voltage, with the motorcycle running and at a fast idle the voltage is 14.4 volts. That sounds a little high, but I had been starting and stopping the bike several times and never gave it a chance for the battery to recharge. Also The Transmission sprocket has 32 teeth and the wheel sprocket has 71 teeth.

Hippo sent me a some information.  I have went through all that.
And I have contacted 'hd-buellservice. They sent me the Service Bulletin for the conversion and the conversion checks out correct.
I have been back in contact with HD-Service and they can’t tell me anything other than go see my dealer.

I borrowed a Squair Wave Generator and tested the Speedo's on the bench at 20, 40, 60, and 80 MPH. by inputing a signal into the speedometer.
from what I can tell they both are working as they should.

At this point I’m at a total loss as to what the problem is.

I'm open for any suggestions. Other than tell the owner to trade in the bike.

50Pan

 

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Offline PC_Hater

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Re: Speedo Problems
« Reply #1 on: Wednesday, May 13, 2009. 11:00:51 AM. »
I had a read through the full thread on the EVO board.
That's an interesting problem isn't it?

So, you have a tried a known good sender and a known good speedo. It still reads fast.
Did you try both together? Known good speedo with known good sender?

Has that speedo ever worked right on that bike? It hasn't has it?

Did the original speedo ever read right?

I'm coming around to two possibilities.
One is that you are getting a lot of spikes on the voltage somewhere and they make the speedo think the bike is travelling faster.
Can you power the speedo from a seperate battery and run all the wires externally?

Two is that someone has messed with the ratios in the primary drive.
Does the bike feel as though it is revving too fast for the speed it is going?

1942 WLA45 chop, 1999 FLTRI, 2000 1200S

Offline 50Panhead

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Re: Speedo Problems
« Reply #2 on: Wednesday, May 13, 2009. 11:28:01 AM. »
Did you try both together? Known good speedo with known good sender?  No I have not.

Did the original speedo ever read right.   According to the owner it has never worked right.  He bought it used and it had already been converted by someone somewhere. HD has no record of the conversion.

Two is that someone has messed with the ratios in the primary drive?  I would have thought they would maybe changed either the tranny or wheel sprocket if they did. Thats why I posted the number of teeth on each.

Can you power the speedo from a seperate battery and run all the wires externally?
Good Suggestion. I'll try it.

50Pan
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Offline FSG

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Re: Speedo Problems
« Reply #3 on: Wednesday, May 13, 2009. 03:17:25 PM. »
I'm a long way from home at the moment so cant do much research, forget the primary, when the speed signal comes from the trannie there's nothing in the primary that will effect it's accuracy.

Are the ratios in the trannie stock? Is it a stock gearset?  The speed sensor is looking at the 4th cog, if the ratios have been changed then it may be counting more teeth for one complete revolution, i.e. reading fast.

What is the diameter of the rear wheel?


Offline 50Panhead

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Re: Speedo Problems
« Reply #4 on: Wednesday, May 13, 2009. 04:25:51 PM. »
Riding the bike it don't feel any different than my stock 97 FXD.
Rear tire is a 404 130/90-16.
I have not been into the transmission. I don't think the owner will want me going that far.
Anyway why in the world would anyone gear down a transmission that far unless you were on the drag strip. Most would want to gear it up for higher speed.

But again riding it feels like riding my stock FXD.

What would be the odds of getting two speedometers that give the same incorrect readings when hooked up to a square wave generator?

50Pan
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Offline MMOCGuy

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Re: Speedo Problems
« Reply #5 on: Wednesday, May 13, 2009. 04:45:48 PM. »
50.

Of course there is always the possibility of getting two speedos that are the same amount off but, in my experience with electronics in the old days (When I was a technician), I'd say the odds are that one of the two, if not both, are OK.

First: Be sure that the signal you are getting from the signal generator is the same as the speedos are set for at a given speed. That is going to require that you find out how many pulses per second those speedos require at a given speed (Say 25MPH or 50MPH). Once you know that, you can set the signal generator accordingly and you can then tell with certainty if the speedos are accurate or not.

Second: If the above checks out OK and the speedos are accurate, then the problem has to be in the sensor in the trans. I'm not sure about the Harley setup because I have never studied it, but in many cases, the pickup unit can be adjusted in or out (Closer or further from the gear it is reading). If that is the case with the Harley trans, the sensor should be set right as too far in or too far out could throw it off.

Third: If number's 1 & 2 above check out, then the only other thing I can think of is the problem is an incorrect sensor, gear or combination of the sensor & gear.

It is not likely that random pulses are the culprit nor that 14.4 volts could cause the speedo to read fast. If you were getting random pulses from somewhere, they would be exactly that - "Random" and, at worse, would only cause the speedo to "Jump" whenever it saw that pulse.

I hope this helps.

Norm.

Offline FSG

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Re: Speedo Problems
« Reply #6 on: Wednesday, May 13, 2009. 04:46:32 PM. »
Quote
What would be the odds of getting two speedometers that give the same incorrect readings when hooked up to a square wave generator?

pretty slim

can you temporarily cluge your '97 speedo onto it (gaffer tape, etc) to see if it also reads low?

perhaps a bit painful but pull the speed sensor use some whiteout to mark a tooth have another rotate the rear wheel and count the teeth on 4th gear to see if it's stock

Offline Evo160K

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Re: Speedo Problems
« Reply #7 on: Wednesday, May 13, 2009. 05:36:10 PM. »
50Panhead,
If the transmission drive sprocket had been changed, say to a 30T or 34T, would that have a bearing on the speedo reading?  I'm too tired at the moment to think that through.

Offline 50Panhead

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Re: Speedo Problems
« Reply #8 on: Wednesday, May 13, 2009. 06:55:36 PM. »
"If the transmission drive sprocket had been changed, say to a 30T or 34T, would that have a bearing on the speedo reading?  I'm too tired at the moment to think that through."


As I posted I have a Transmission sprocket with 32 teeth.
What is the Stock Transmission sprocket?

I have little other choice than to install the speedo out of my FXD for testing. It it reads fast it has to be in the gearing there will be nothing else left to check.
If I had a good O-Scope that I could hook up to the sender unite I could check the transmission gears that way. But I don't have one.

I have got more time in this than I want. I can't charge the guy for someting I can't fix.

Thanks everyone.

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Offline Evo160K

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Re: Speedo Problems
« Reply #9 on: Wednesday, May 13, 2009. 08:18:00 PM. »
32T is stock for all models according to the 1995 parts book.

I didn't see a speedo with the number 71014-95 in that book or the 1997 parts book.  Don't have a 96 book.  Zanotti doesn't show a listing for it either.  I'm not sure what that means however, if anything.

Offline FSG

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Re: Speedo Problems
« Reply #10 on: Wednesday, May 13, 2009. 10:09:06 PM. »
Stock is 32T Front, 70T Rear

For a '95 FXD:  67025-95C SPEEDO KIT

For a '96 FXD:  67025-96C SPEEDO KIT

At the moment I don't know the difference but I'll check.

What is this modification that you have done?  Changed from a cable speedo drive to a VSS from the Trannie?

That 71014-95 is invalid.

Offline Evo160K

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Re: Speedo Problems
« Reply #11 on: Wednesday, May 13, 2009. 10:26:26 PM. »
50,
If your customer just wants the speedo to read correctly, can you just add one of the Dakota Digital calibrators between the pickup and the speedo and adjust the pulses so it does.  Mine cost about $100 and has been trouble free for 2-3 years now.  I converted from a mechanical to an electronic speedo.

Offline FSG

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Re: Speedo Problems
« Reply #12 on: Wednesday, May 13, 2009. 10:42:40 PM. »
50,
If your customer just wants the speedo to read correctly, can you just add one of the Dakota Digital calibrators between the pickup and the speedo and adjust the pulses so it does.  Mine cost about $100 and has been trouble free for 2-3 years now.  I converted from a mechanical to an electronic speedo.

 :up:  yep easy fix

Offline Princess Butt

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Re: Speedo Problems
« Reply #13 on: Thursday, May 14, 2009. 02:11:40 AM. »
Back in '97, when I bought my Road King, the dealership said they were having problems with people changing out their plug wires and it screws up the speedometer readings. However, my understanding was it was a random event (would cause the needle to jump, mess with the odometer display, etc.).

Is the mileage off as well? Take a measured course of exactly 10 known miles, ride it with a vehicle with a good working odometer and speedometer. Then take the same exact course with the bike. Does the odometer read the same number of miles? You can also do this with a GPS unit which records where you have been and indicates speed.

When I was a kid, we had a Ford station wagon where the speedometer always read low. They never could get it working right. It was off by 15 mph at 60 (reads 60 when you were going 75).

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