How accurate or otherwise are the std speedos on VTR's ?

LotusSevenMan · Post by **LotusSevenMan** » Sat Mar 10, 2007 10:33 pm

Reason I ask is I have a 15t front sprocket instead of the 16t one. Wondered how far out it is to start with before this mod was done.
I have a Sigma push bike speedo in the shed but am yet to fit it.

I had an indicated 140mph with more to come before I decided that the M20, err sorry, private test track was not the place to be doing this sort of 'testing'.

I can say that at a steady 102mph indicated it was reading 5,500rpm.
Is there a miles per hour per thousand RPM figure anywhere?

rst steve · Post by **rst steve** » Sat Mar 10, 2007 10:47 pm

Just been out on mine on my "private test track"and 100 is about 5500rpm on standard gearing if this helps

LotusSevenMan · Post by **LotusSevenMan** » Sat Mar 10, 2007 10:51 pm

My maths is probably adrift, but if the speedo is 'accurate' at 140 normally then the sprocket mod makes this 131mph??????

Given a 10% speedo error on the 140 = 126mph. With sprocket change = 122/3mph?

Anyone know the correct percentage error on a Honda VTR speedo (rather than my guessed 10%)?

LotusSevenMan · Post by **LotusSevenMan** » Sat Mar 10, 2007 10:55 pm

RST Steve.

Is that a 16t front and 41t rear then? This is the std supplied-from-Honda set-up!
I saw you see from a previous posting on 6th March that you were changing to the M & P Stealth sprockets.

Bondy · Post by **Bondy** » Sun Mar 11, 2007 8:31 am

I've just put a push bike speedo on mine so as soon as i get it set up ill let you know how far out the standard item is.

LotusSevenMan · Post by **LotusSevenMan** » Sun Mar 11, 2007 9:02 am

FSM.
You should try 'darn sarf' as we have more cameras than Jessops, Currys and Dixons put together.

My bike speedo is a Sigma BC1600 so I'll go read the instructions yet again and see if I can understand them. I mean, it's so unfair as the instructions are far too complicated for me; they are written for an eight year old to set it up!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Kitch · Post by **Kitch** » Sun Mar 11, 2007 11:28 am

I'm on a 15t front too.

Error seems to be ~10% factory and maybe another ~10% for the sprocket.

My little sigma type thing showed me a true 30 was reading 36 on the speedo and a true 80 was 92.

Judging from that, best guess suggests that 140 indicated is around a true 125.

LotusSevenMan · Post by **LotusSevenMan** » Sun Mar 11, 2007 12:12 pm

Thanks Kitch.
Just had another VTR mate around (I was resetting his carb balance) and he set the Sigma up as the rolling distance was 1,870mm etc.
I'll try and fit it all soon then (ie. today!!).

Yesterday when I was out I forgot to say that I was following a few cars through a well known Scamera set @ 50mph. I had 56mph showing on my speedo and was pacing the cars accurately (and have to assume they had their speedos showing 50mph too including their speedo errors). That seems to follow approximately what your speedo readings were.

Fireman on a Storm · Post by **Fireman on a Storm** » Sun Mar 11, 2007 2:55 pm

rst steve wrote:Just been out on mine on my "private test track"and 100 is about 5500rpm on standard gearing if this helps

It would be the same number of revs to speed on a 15t or 16t because the speedo pick up is on the gear box before you get to the gearing on the sprockets!!!!

rst steve · Post by **rst steve** » Sun Mar 11, 2007 4:25 pm

LotusSevenMan wrote:RST Steve.

Is that a 16t front and 41t rear then? This is the std supplied-from-Honda set-up!
I saw you see from a previous posting on 6th March that you were changing to the M & P Stealth sprockets.

Yea that is 16t front and 41t rear. Was thinking of changing the gearing on mine but think i am going to leave it standard now as i do quite a bit of motorway riding so like my top end speed also dont want the speedo to be out as there is loads of speed cameras round here

Fireman on a Storm · Post by **Fireman on a Storm** » Sun Mar 11, 2007 5:05 pm

rst steve wrote:
LotusSevenMan wrote:RST Steve.

Is that a 16t front and 41t rear then? This is the std supplied-from-Honda set-up!
I saw you see from a previous posting on 6th March that you were changing to the M & P Stealth sprockets.
Yea that is 16t front and 41t rear. Was thinking of changing the gearing on mine but think i am going to leave it standard now as i do quite a bit of motorway riding so like my top end speed also dont want the speedo to be out as there is loads of speed cameras round here

If you change the gearing to a 15t front your speedo will be on the side of safety..

On my cousin's TLs his speedo was 7% out at 100mph. The speedo showed 107mph.

At 30mph true speed you speedo would show 32.1mph

Seeker 77 · Post by **Seeker 77** » Sun Mar 11, 2007 5:14 pm

Use a gps?

beckster · Post by **beckster** » Sun Mar 11, 2007 5:23 pm

Hi all,i fitted a 15t on mine then installed a speedo healer.I used my gps from the car taped to the tank,and took the two readings,one from the gps and one from the 'storm speedo.According to the speedo healer calibrating program the 'storm speedo was out by 11% using a 15t front and standard rear.

Hope that clears up the debate

LotusSevenMan · Post by **LotusSevenMan** » Sun Mar 11, 2007 5:54 pm

Well I got the bike computer fitted today and found the performance was brilliant. It has added loads more HP or something 'cos I was able to reach a bike speedo indication of 199.9mph. That was just cruisin' too. Mind you, all the cars were staying with me as well.

OK, OK! So I (actually my mate!!!) got it wrong. Forgot to do the KPH to MPH division of 1.61.

Now sorted!!!
A steady 50mph indicated is an actual 44.5 and at an indicated 90mph it is actually showing 82 on the Sigma bike computer.

Just about 9% error (ie. 100 is a real 91)

This means my indicated 140mph yesterday is actually 128mph; no, wait.
Err, sorry officer that is with error correction actually a speed of 70mph; spot on!!!!!!

Post by **sirch345** » Tue Mar 13, 2007 10:13 am

LotusSevenMan wrote: I was able to reach a bike speedo indication of 199.9mph.

I must do that airbox mod