hi , new to the forums and new to ducati....just recently got a 2000 900ss and I. Having tach issues from the gate.. so when I start the bike the needle goes to 4K rpms and never goes any higher .....as I ride it never moves, but occasionally at around 80 to 100 mph it will bounce between 0 and 4K rpms....never ever going higher......I just wanna know where the computer gets its tach information in the gear box/engine...and if I can rule that out and either decide to pull the tach apart very carefully or just get a used one on eBay for 80$? A little advice is all I need, how would I go about using a process of elimination to find the problem ? Thanks !
Tacho on these bikes is electronic, getting it's signal from the ECU. You should check your charging voltage. One of the first signs of a low charging voltage is a low or no revcounter reading.
Ok I haven't checked the voltages but I was assuming it was mechanical because of the way the needle won't move past 4K rpm and isn't effected at all by the rpms. . Where is the sensor that the ecu uses to read rpms?
I take it that you have ruled out something as simple as the needle tip touching the gauge face (and jamming) or similar?
Nit well no , the way it's acting is like the needle wants to go past 4K but gets stuck. Even my local Ducati dealership said it seems like that ...engine runs well ,though it feels like I only have one piston firing at idle . So if the sensor was bad the next I would have other issues with the bike right ?
symptoms are the same - it probably isn't this but you need to examine needle carefully to confirm it's not jamming on face so you can rule it out. I only mentioned it because i've seen it with my own eyes on both car tacho and speedometer.
Ok cool, well I’m gonna get to dig into the problem on my day off this week, but till then I have a wierd observation...... When I start the bike the tach goes to 3.5 k...if I give it throttle it goes to 4K and never goes beyond, but when I go over I go over 80mph it goes backwards ...as I give throttle the tach DROPS DOWN with the more throttle I give it ! Like it’s backwards, and if I let off the throttle it goes back to 4K.....the more throttle I give it the LOWER it goes....like down to 1k....it’s acting backwards once I go over a certain speed, or maybe it’s the gear I’m in ...not sure which butthey go hand and hand ? Anyone ever seen this? Could a wrong wiring or bad contacts do this?
From extra symptoms you’ve added you can almost certainly rule out my suggestion now, It sounds far more complex.
Yes, it's almost certainly an electrical issue. FYI, there is a crank position sensor which supplies the ECU with a signal that it uses to determine the engine speed, spark timing and injection timing and as long as this signal is present (i.e. the engine is turning over) it will keep the fuel pump relay energised this providing power to the fuel pump, coils and injectors. If the crank position sensor was faulty, believe me, the bike would be suffering from far worse problems than a faulty revcounter. The symptoms are often those reported prior to the failure of the voltage rectifier/regulator.
Awesome, thank you,I wanted to rule out the sensor ..so are you saying the symptoms I’m seeing can be the asign of a oncoming voltage reg/rev failure?
I'd put my money on the rev counter simply being knackered. Had similar problem with the one on our Monster.
To note did my charge put put. It's 13.5 v max when I rev. Did a leakage test. It was .7 mamps and it said it should not exceed .1 Ma. Saying maybe I have a short. I think it's the tach throwing it off
It might be cheaply fixable , but this is a long shot .... 10 years back , the tacho on my ST4 started acting up .... can't remember exactly what it was showing , but nonsensical readings anyway . The root of the problem turned out to be the small white connector on the rear of the tacho unit . Its fiddly and flimsy , and it has the usual " click in " retainer / tab / thingy to lock it . The female half of that connection ( the part inside the tacho ) is soldered on to a thin cheapo bit of circuit board , and there's nothing supporting it apart from the solder , and that's were the bad contacts were . The printed circuit tracks on that board had lifted and broken loose . That tacho lead is going to vibrate , and so will the clocks ( at certain revs ) and that mechanical load is getting dumped on to that pitiful runty socket, and a bit of circuit board ! I can give details of my fix ( or bodge ) if anyone is interested ..... ... it was a bit gory , but it was cheap , and it has lasted over 10 years and many thousands of miles ...... and it's not visible . I don't know what a new tacho unit costs .... ?
I think any guide helps someone eventually, but it’s looking more and more that I’m going to have to pull the tach apart.....you can get certified used ones for $80 on eBay but I’ll try fixing it first.....
OK - All from memory , no photos available Completely remove the tacho unit from it's holder after disconnecting the stupid white connector and removing the lamp . You should have just the glass dial with the plastic body behind it and they are sealed together . I "dremmed" it open about half way along the body so that I could remove the back portion , but a junior hacksaw should work ...... keeping a close watch on the depth of the cut . Then I soldered my own wires directly onto the circuit board and fed them out through the same hole that the white plug goes in . To make good , I used epoxy to repair where I had cut the body in two , but first I made a couple of holes in the back portion , to thread a cable tie and anchor my new wires . After that , you can just make a new connection back to the original wiring. Use a male/female pair of 3 pole connectors if you want an easy disconnect in future . I went the lazy way and just soldered the wires together , with shrink tubing to finish . It could be good topic for a new thread ? " Post your best bodge ... or any kind of cheapo fix ! "
Lucky it isn't the mechanical tacho that was fitted to carb models.......when the worm and pinion drive fails it isn't a cheap or an easy fix unless you switch to an electronic tacho. You would need the drive gear, an oil seal and two camshaft bearings, plus rocker gaskets and the silly camshaft nut.
