Rev and speedo needles going up and down

[Slaninar]

Took the bike for the sea last few weeks. Lots of nice twistyes. No problems at all, except occasionally speed and revs "needles" would drop down to zero, simultaneously. Stay down for a second-two. Then go back to where they should be. Such things happened when I was holding steady throttle usually, or slowing down just slightly. It would usually happen twice, then not appear for a while. Is it some speedo breakdown, electrical problem, or an malfunction code?

The bike is 2001 FZS600. KN air filter, open end can, dyno jet kit.

[AdieR]

Has the bike had work done recently?

FWIW, I'd check the wiring first for chafing / rust / loose connections / water ingress in any connectors (as both gauges are affected, I'd look at earth points first).

[Slaninar]

No work. Just oil, filters etc. Brakes as well. OK, I washed it once this spring. But it's been 30 + C, hot, sunny, no rain riding. Voltage seems fine, on the battery. 13 volts on idle, 14,5 on 4k plus revs.

[red98]

that sounds like a loose/corroded connection,have a look at all the connections make sure there clean and secure 

[Slaninar]

that sounds like a loose/corroded connection,have a look at all the connections make sure there clean and secure 

I checked them just this morning. Plus (red) wire on the battery was a bit loose. I screwed it in tighter. I also checked all the cable connections and fuses. They looked clean and tight, so I just put some WD40 and connected them back.

Will take it for a test ride and see what happens.

Anyway, since it is happening occasionally, it should not be a mechanical problem with speedo on the wheel, right? :/    I did open, clean, put some lithium grease on that, but I couldn't have broken it, it would have just stopped working at all?

[AdieR]

The fact it happens occasionally sounds to me like an electrical problem, and the fact 2 gauges are affected is a giveaway (if it was a failed speedo sensor, why would it affect your rev counter?)

The fact it's intermittent makes it hard work to track down (temperature / humidity / mechanical movement and all sorts of factors can have an influence), but it can be done.

As silly as it may sound, does it happens with steering action? ie, could a wire be getting trapped / pulled with the bars? Or could a chafed wire be coming into contact with the forks as they move? (Plugs / sockets may be clean and tight but its worthless if the wiring is damaged in between. Bear in mind manufacturers can be a bit tight with wire lengths (cost) and don't always leave much "slack" on wiring looms.

If the wiring to the dash is ok, then its a case of following the wiring back to the ECU and any sensors (throttle position sensor and speed sensor wiring esp, on the later FZ6 there is wiring relating to both sensors), (I'm not familiar with the setup on the FZS bikes and haven't got diagrams for it either) and making sure they're clean and tight as well (bear in mind engine-mounted sensors and wiring get exposed to temperature fluctuations).

My guess is you've got either a loose wire (vibration / heat), or corrosion (traffic film from the road) on an earth point somewhere (earth points are almost always the weak link in the chain).

IMO a faulty sensor is unlikely (see above), and a battery / fuse fault is unlikely (different symptoms).

[YamFazMan]

Hi
Just a thought
https://dl.dropbox.com/u/70564722/img025.jpg
ATB YFM

[His Dudeness]

does it happen when you have your indicators on?

[Slaninar]

It used to happen when engine was warm, after some half an hour ride. From what I noticed, it was more like 1 or 2 seconds to zero, then back to... hmmm I'm sure it was back to where it was orignaly right away. But maybe 4000. 3000 no way, that's too low, sure it wasn't.

I put wd 40 on all the contacts, made sure they're nice and tight. Took it for a test ride yesterday and it seamed fine. Will test it a bit longer tommorrow. See if it happens again.

It doesn't happen when indicators are on. Only when going at a steady speed after some hard cornering. Maybe it happened during cornering as well, but my eyes  were on the road, lorries and hot chicks throwing their bras on me.

[Dead Eye]

What was a lorry doing wearing a bra!  :eek

Sorry, couldn't resist

[bikemad62]

Don't know if this is of use but still. The rev counter jumping up and down could be speedo speak for the tps (throttle position sensor ) is dead. It usuall goes up to about 3k on the clock. as for the speedo check things like the lugs on the spinning magnet at the wheel and the routing of the wire. I very successfully managed to cut the cable with the new shiney wavy disks i had put on. but it didn't go straight away. the speedo went up for a while then would jump around. Then read 70 when i was sitting still then no more speedo. The smoke from the clocks was impressive. Scared the hell out of me :rolleyes  I realise the problem may not be related but i thought the info may help with a diagnosis.

[Lazarus]

That happened to me (and probably contributed to me getting a ticket!!!!)

i thought it was battery (changed it and hasnt happened since)

what i did find was that when the needles dropped (and stuck at 0) pressing the brake brought them back to life.

After speaking to a mechanic he told me he had heard of this scenario and pointed to electrical contacts (probably ones hidden under the cowl)

[oldmotherfoccer]

i think its called the speedo drive dog

[oldmotherfoccer]

OK Deefer666 says that depending on where the needles point it is one of 3 things

1) TPS Faulty and the rev counter needle will give the fault code
2) The magnetic tips breaking up from the ceramic drive dog (very common if the front wheel has been removed by an unexperienced mechanic)
3) The speedo sensor wire wearing through on the brake discs due to being incorrectly routed

[darrsi]

17,699 posts!!!!


Jeez.......you should know the inner workings of everything.......why are you receiving advice?  :lol

[Deefer666]

OMF is my other half and has been on here from the very early days, cos I dont get a chance to get on here much she normally asks me the question and she types in the answer & seeing as though I have worked on more fazers than I can remember, yeah I pretty know them inside and out

[darrsi]

Cool...... 

[Slaninar]

After checking wires, tightening contacts and some WD40 on them, the problem has not yet appeared. However, today I will have time for a longer ride, to really warm the bike up and see if it happens again.

Taking wheel off by an unexperienced mechanic? HEY, that's me! 
Though I've done it several times before without any problems.

Cable routing: no, doesn't touch the disc.

[Dead Eye]

Typical, when I was first reading this thread I was thinking "I'm glad mine doesn't play up..."

I jynxed it

It had been under cover for 10 days so didn't see any real bad weather and hadn't even moved an inch yet I started it up to go out yesterday and on my journey the speedo has magically decided to fly up and down the gauge at its own discretion. I think it may have had a tantrum because I left it alone for too long Time to go see if I can fix it / break it more...

[Slaninar]

Still no problems. Tightenet loose plus contact on the battery and put wd 40 on all the connectors beneath the fuel tank, made sure they connect nice and tight. Guess it did the trick.