Rev counter not reading correctly

[Madderz]

Hello again guys, think this is in the right place this time. I've searched everything to do with rev counter and rpm and can't find anything in the forum.

Another fault to add to my list on the new bike. The rev counter seems to be reading incorrectly!! When sat idling i can tell by the engine note that it is idling just above 1k ish which to me is fine but my rev counter is saying its idling at 4K!! When i bought the bike and rode it home the rev counter was spot on but i noticed the other day when i was giving it some welly that the rev counter was actually off the scale (past 16k).

I took it for a quick blast one day and it seemed to jump back down to the right place but then ever since then its now sat too high? I know it's definitely too high as the limiter is set at 14.5k (if i'm not mistaken and it flies well over that before it kicks in).

WTF is going on? I thought the rev count worked off the speedo cable or similarly off the gearbox. My speedo seems correct going by other traffic, engine note and my experience going at 30?

How do they work? Has it "jumped a tooth" or so to speak on its internals? Has the needled popped of what it sits on?

[cargo]

The rev counter gets it's signal from the CDI box................it is defo not connected to the speedo drive or gearbox


Low battery voltage can cause it to behave strangely

I have also seen my rev counter read exactly double what the revs actually are...............it seems to happen only on wet days or sometimes the day after a wet race.................I've always just assume it was water getting in somewhere and the fault goes away again soon after.

One of the many electrics experts on here will be along to explain it soon I'm sure

[JamieNeve]

Mine has also done it in the past a couple of times, I give it a day or two and it normally corrects itself.

[CaNsA]

My rev counter hasnt worked for about 8months.
It moves about 2mm and thats it.

I'll fix it one day.

[Madderz]

Ahhhh so seems they are a bit funny anyway
it hasn't really come into contact with water since I've had it, been super sunny here in Bournemouth! I'll leave it for a bit see if it settles down. If not I'll dig deeper. Just a bit concerned as after I've balanced carbs I'd like to set the idle nicely and make sure all is good through the Rev range. If its bust then I'll just tell people rev counters are for girls. Lol

[banner001]

get your bike up to 30mph in 3rd, tacho should be reading around 4200-4300 rpm.

ditto on the bad battery, mine was causing the rev needle to "float" around at 8k, if i held it at 70-75mph in top gear the rev needle would jump up and down from 6-9k rpm, new battery and its not been an issue since.

[Madderz]

get your bike up to 30mph in 3rd, tacho should be reading around 4200-4300 rpm.

ditto on the bad battery, mine was causing the rev needle to "float" around at 8k, if i held it at 70-75mph in top gear the rev needle would jump up and down from 6-9k rpm, new battery and its not been an issue since.

Ok I just span it round the block. 30 in 3rd reads around 8.2k, idle is a little higher than normal as I was messing with it sound like it's idling right but reading 4k?

Maybe it's done the double trick on me? Weak battery you say? Starts fine everytime even after I've flooded it, still loads of oomph with the starter.