Viper - Erratic speedo and tach

Viper Bush

Viper Bush

New member
Joined
Dec 15, 2012
Messages
29
Age
39
Location
MN
Needs some help diagnosing the issue with my speedometer and tachometer on my stock 02 Yamaha Viper. They both bounce around erratically. From what I've ready, the tach is electronic and the speedo runs of of a pick-up sensor next to the drive shaft under the clutch. So it sounds like I have two separate issues...I have an electronic issue with the tach and a mechanical issue with the speedo? True? Could it just be a bad speedo sensor? How does the sled read RPM and send it to the cluster?

The sled has 2600 miles on it. The drive shaft bearing on the clutch side looks good upon inspection. There is a gear on the end of the drive shaft and an electronic pick-up sensor mounted near it. (Seems to work similar to an ABS sensor on a car). Everything looks the way it should, as far as I can see. I checked for loose, worn wires and couldn't seem to find anything. I'm at a loss. I need to get this sorted out before we get more snow! First 3 inches today finally and carbs are clean and sled is ready to go...except for this issue...HELP!


http://www.youtube.com/watch?v=G4mZRsLjgWE



 
does it do anything differnt if you switch the headlights from low beam to high beam while running?

is this a er model with elc. start and reverse?
 
This is a non ER Viper. No electric start, no reverse.
I Just ran out to the garage and tried...doesn't seem to make any difference with hi beams vs. low beams. Any other ideas?

I should also note that the tach issue seems to be somewhat intermittent...sometimes it works just fine. I just noticed the tach start acting up after the last ride, last year. The speedo has never worked properly since I've owned the sled.
 
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well its either the wire harness rubbed thru or the guage is funky.

if you know someone else with a viper to just plug in thier unit see if it does the same thing.

the speedo is pulsed by the sensor down under the sec clutch, thats likely bad, seen those go bad before a few times.

tach is just a voltage tach so thats why i said could be wire harness chaffed. youd know in 30 seconds by trying a another known unit. I possibly have one you could try if you dont know someone closer by..
 
Unfortunately, I don't know anyone near me with the same sled. Would you recommend replacing the speed sensor first, as I figure that's cheaper than buying a new/used working cluster? But now that I think of it, the sensor would only fix the speedo issue (if that's what's wrong) and the tach would be messed up still. Could it just be a bad cluster? Got any laying around? What does a good, working used speed sensor and cluster sell for these days?
 
Viper Bush said:
Unfortunately, I don't know anyone near me with the same sled. Would you recommend replacing the speed sensor first, as I figure that's cheaper than buying a new/used working cluster? But now that I think of it, the sensor would only fix the speedo issue (if that's what's wrong) and the tach would be messed up still. Could it just be a bad cluster? Got any laying around? What does a good, working used speed sensor and cluster sell for these days?
Click to expand...

Also, not sure if it's normal, but my whole cluster blinks (lights go out, gauges go out) for a split second when I switch from hi beam to low beam and visa versa. I just assumed this was normal?
 
Well, I pulled the harness back out from under the motor and found a couple bare wires, as suspected. I taped it back up, put everything back together and gave it a shot...now the tach is working fine, not fluctuating/bouncing around anymore. The speedo still seems to be an issue. It now constantly stays at 0. It no longer bounces around though.

Could it just be a bad speed sensor? Any way to test the speed sensor to see if it's bad?
 
Viper Bush said:
Well, I pulled the harness back out from under the motor and found a couple bare wires, as suspected. I taped it back up, put everything back together and gave it a shot...now the tach is working fine, not fluctuating/bouncing around anymore. The speedo still seems to be an issue. It now constantly stays at 0. It no longer bounces around though.

Could it just be a bad speed sensor? Any way to test the speed sensor to see if it's bad?
Click to expand...

good, glad you fixed the 1 problem.

for the speedo sensor have you checked it with a multi meter to see if its open or shorted? How many ohms do you get for it?
 
I have not tested the speed sensor yet, no. I suppose that would be the next step. I'm not even sure where it plugs into the harness, but I'll figure it out once I get in there. What should I see while testing the sensor? ...I don't have a service manual.
 
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In addition to fixing the harness rub through, as I mentioned previously, I replaced the speed sensor with a working used one and now everything is working as expected. Happy sledding!!!
 
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