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Tacho running at half speed
Posted: Mon Apr 08, 2013 11:31 am
by Keenaz
Hey guys new to the forum. I have a VFR400 track bike but the tacho runs at half speed i.e. 7000rpm is about redline! The guy who sold it to me bought it like that and is not sure on how to fix.
Any thoughts?
Re: Tacho running at half speed
Posted: Mon Apr 08, 2013 11:39 am
by magg
More detail, surely not an oem tacho?
Re: Tacho running at half speed
Posted: Mon Apr 08, 2013 11:47 am
by CMSMJ1
You'll be needing a VFR tacho - yours will be an RVF one.
The bikes run totally different pickups..
Re: Tacho running at half speed
Posted: Mon Apr 08, 2013 9:58 pm
by Keenaz
Cheers guys. No its not an OEM, its a track bike thats been down the road more times than can be counted haha.
I can take a photo if that helps? I think the whole setup is OEM so not sure if I can just replace it without replacing everything else hmmm.
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 12:39 am
by Cammo
Pics would help.
Both rvf and vfr tachos can be removed no problems from the dash.
They look different and aren't interchangeable between bikes/electrics.
VFR tacho:
RVF tacho - rev range starts at 6 o'clock position:
Hope that helps.
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 1:57 am
by Morespeedvicar
Try changing its timings if its an after market one, theres prob a dip switch on it somewere to set it to the right number of cylinders.
Cheers
Ian
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 7:25 am
by thunderace
Not always that easy Ian due to the firing order being 360*. Some tachos just won't work on a V4 360*.
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 7:54 am
by Cammo
NC30 coils also run wasted spark (spark on exhaust stroke also) so if it's an aftermarket tacho it further confuses things.
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 10:55 am
by Neosophist
thunderace wrote:Not always that easy Ian due to the firing order being 360*. Some tachos just won't work on a V4 360*.
I think thats backwards...
The V4 360 (ala NC30 /NC35) runs a wasted spark system like most standard inline 4s do (zxr cbr etc etc) so setting the rpm is the same.
The V4 180 (ala NC24 / VFR750) runs 4 separate coils so you often dont end up with the right multiplier (x4) as opposed to x 2 needed for NC30.
Re: Tacho running at half speed
Posted: Tue Apr 09, 2013 4:05 pm
by Morespeedvicar
Yeah thats wat i thought, they run the same as a inline four, each pair of plugs (one coil) fires every 360 dregrees, but with 90 dregree separation between the two pickups rather than 180 that inlines run, 180 degree v4 are a hole world apart tho! But i would think each single coil would still spark every 360 degrees so pulse wise if signal was taken from one coil input it wouldnt make any differance.
Cheers
Ian