Funny tacho readings

[Petrolhead]

My tacho seems to have a life of its own, sometimes quite stable other times jumping wildly......is this a really a problem somewhere on here David Thompson said relay 30 could cause unstable connections to the CDI, hence the tacho feed voltage being interrupted/intermittent?

I have two tacho's and they both jump so they can't be both the problem or can they? I have ordered a wiring diagram from ebay.uk , failing that I am thinking of going with a mechanical driven one but its expensive.

Anyone got a source in the Uk of good aftermarket relays?

[DAVID THOMPSON]

loose wires and connections
dave

put a gps on it and know how fast its really going
and forget the tac

[Petrolhead]

Dave, I replaced the relay after finding your old posts on here, it was no problem doing it. Seems like its a vibration issue with the tacho cos if you remove it from the housing to isolate it from vibrations, then plug it in, it reads smoothly but jumps as soon as it is bolted up. I'll try a bit of silicone around the plug to hold it firm ( possibly loose tacho plug contacts) but if it doesn't work I think i'll go with the SR500 mechanical tach option , I have to have all my bikes just right

Thanks for your reply and info

[Petrolhead]

Just if anyone is experiencing this problem, I have been able to sort it out almost perfectly so the tacho reads smoothly over 98% of the rev range. I noticed that at certain engine revs 4-5k the vibration harmonics caused the whole instrument console to vibrate up and down and the tacho protested by waving its needle wildly.

Using Honda battery box rubbers and made up longer inner sleeves from 10mm heating oil pipe , the binnacle is properly isolated from engine vibes now, I also made up a small clamp to hold the tacho power signal feed plug firm to the tach, fastening it to the right hand side lower tacho mount so that the plug was not vibrating around its socket. I also used added more cushioning rubbers to the instrument to bracket joint.

That along with a new main supply relay also isolated from the frame with a rubber mount, means that the engine runs good and the tacho reads fine with only a momentary waver around the 5.5K mark.

[Nils D]

I've experienced the same problem with my tachometer.
I've had it for service a few times, I've had the electronics replaced - still it behaved in a more ore less hysterical manner. The only fix that has really worked is to have removed the bolts holding the dashboard.

[Petrolhead]

Just an update, Nils.....it read smoothly when on the side stand but after taking it for a run it was just as bad as ever. So I opted for a mechanical tacho from the SR500, using a XTZ660 drive and cable , I also transferred the needle from the MZ one to the SR500 tacho to make it look similar, the SR500 tacho has a black face and looks quite nice with the white face speedo

[DAVID THOMPSON]

looks nice
but hope you have a box of the watches in stock....
as the vibration will destroy them in short order
dave

[Petrolhead]

Yes, the very thing that makes a single have appeal does that, I'm hopeful but not too hopefull