nc24 tach reading wrong, any suggestions?

[suzbug]

Hi guys.
Got the bike running ok and now have an m.o.t, but the tacho shows about 3000rpm at tickover.
When riding the bike it red lines in first at 30mph but just feels to be coming alive as the needle goes off clock.
I thought an nc24 should do 60mph in first?
Is there any way of checking or fault finding?

Thanks in advance
suzbug

[Neosophist]

NC24 won't do 60mph in first gear, your confusing it with an NC30.

Maybe it's idling too high? i.e. 3000rpm?

It should idle at 1250.. turn the idle screw down.

You have a rev limiter built into the bike.. rev it in first till it wont rev anymore, your needle should be in the red when you feel the ignitionbox cutting the revs out.

If this happens sounds like your tacho is ok, tbh they either usually work or dont, in which case your bike is probably idling way too high!

[suzbug]

Thanks neo.
How fast should I be going in first when it redlines?

The engine really doesn't sound to be idling at 3k, infact my m.o.t tester even commented that the tacho was wrong and said it sounded to be idling right. If I lower the idle speed it stalls. It really doesn't sound to be running at 3k.
I gave it some gas on way home and the needle went into and out of the redline without any noticeable restriction.
is it possible to be displaying double the actual engine speed?
If anybody can post some speeds in first gear at say 10k rpm and I can check that against mine tomorrow.
At least I will be able to compare against another bike.
I can't think of another way to determin if its out and by how much.

Thanks
Suzbug

[suzbug]

hi guys
right, its definatley the tacho reading wrong, i came into work on it this morning and on the M1 i was doing about 65mph in 6th gear and the tacho was reading 10k rpm!
surely this isnt right!??

Im hoping the tacho is reading double what it should, which would make sense as the engine is only just comming alive when it gets to 12k on the tacho..

any suggestions??

Suzbug

[Neosophist]

Did you hit the rev limiter?

It does sound out though.. either that or your speedo it out (more common)

Do you have a speedo convertor on it? Or has the needle been messed with? do you have anyone that can drive along side you and confirm what speed your going is actually what it says on the speedo?

105km/h (65mph) should be aobut 7000rpm ish in 6th if I recall.

[suzbug]

hi ne.
no i didnt attempt the rev limiter, it was my first real trip on the bike since passing my test, (did 2 miles yesterday to M.O.T station) and i was cautious with new tyres, brakes and engine cold etc..
i definatley wasnt doing 130!
it was along a dual carriageway and i was following a corsa, so i think the speedo is about right, about 65mph (yes, i have a converter from wemoto, not the sticker type.)

if anyone can give me specific mph for certain rpm in different gears i will be ale to figure out how much it is our by..
i dont want to push the bike by revving too hard, but deosnt really want to brighten up until it displays 9000rpm.

I have bought a replacement tacho from fleebay so will try connecting that up when it arrives... its really odd though..
like you said neo, they would normally just work or fail... just wondered if anybody else has had this or what could cause it??
has a previous owner dicked about??

Suzbug

[Neosophist]

you'll hit the rev limiter in any gear, 6th will be a bit of a struggle.. so you can hit it in first gear by not changing gear until it wont go anymore.

it should hit the rev limiter when its somewhere in the red, 13,500rpm ish?

If your tacho is reading over that it's out.

Don't see how it'd be out though unless somebodys messed with the wiring or theres a bad earth?

Is it an NC24 tacho?

[suzbug]

yeah, its an nc24 tacho.
i bought an nc21 tacho a while ago to try because i thought it might have the wrong one on but the wiring connector is different and redlines earlier so i didnt fit it.

i will check the earths on the bike. it is definatley reading high, i will bet my V5 on it. very odd though..

where do the tachos get the information from?? how do they get the information??

[CMSMJ1]

They count pulses and work out the revs from that. The CDI tells the tacho what goes on and the tacho shows it..but if the CDI has the wrong info then what can it do?

Can you hit the rev limter in 1st or 2nd? into the red and out so the engine cuts cylinders?

EDIT - see you have just passed test etc - hitting the limiter is not a natural thing to do so I understand your reticence to just cane the bike and smack the limter.. It also goes against any mechanical sympathy you might have. You easiest way is to get a clear enough road, leave it in first and just keep it pinned. You'll hear and feel it hit the limiter (which is a soft limit - nothing mechanical is going to smash into each other..the CDI just will say, whoa boy!! )

Obviously..with you having issues with this...it might not hit a limter..so it might be useful to find out what the limit should be from someone else as if the osft limit is missing and it allows you to over rev then you can be looking at big damage...and we don't want that!!

So my advice...don't go revving it til someone tells you the soft limit and then go and rev to that - you can hit the limit and not blow the engine then

[suzbug]

thanks!

i did give it some revs this morning and the needle went into and out of the red, ie, it went straight through and off the clock with no hesitation so no signs of a limiter there! which it wont be if the engine is in fact only doing half, so 8k..
i dont mind looking for a limiter, but my first journey on the bike was in rush hour M1 traffic this morning so wasnt really appropriate or safe to ring its little neck!
when i get home tonight i plan on dropping off the bag and going for a pleasure ride to get a feel for the bike.

can the rev limiter be taken off?? has a previous owner dicked with this do you think??

Thanks
Suzbug