Is the gearing affecting my speedo?

[BluprintZ]

I posted a thread a few months ago, when fitting a new chain and sprockets to my M900.
I opted to fit the 14T engine sprocket, as opposed to the standard 15T one, due to the lumpty nature of the beast in town riding.
No probs with the performance of the bike, much smoother on take-off and first gear doodlin' in town.
A while back, i posted about me getting a pull from the plod one Sunday afternoon (no s******ing at the back please!!).
He said i was doing 92mph, although i didn't go above 80 at any time, honest guv!
Fast forward to last Sunday, i had a tootle out up the mountains of Snowdon national park, with me mate on his mid-eighties 1200 Hardly Dangerous Sportster.
When we got back to my place after the run, we had a chat about various parts of the ride and one of the bits mentioned, was when he was following me along a fairly straight bit of road, at what again i swear was 80-ish mph.
Mr Hardly said "no way", he was clocking me at 97 at that point!!
This was with the 14T sprocket on, when i got the pull by the plod (i won't tell you again), several months back, i had the 15T one on.
Any idea's what's going on?, am i really doing 30mph when the speedo says i am?
And yes, before any smarty's ask, i have had the needle over eighty, several times...well, a few times anyway!

Regards,

Concerned (potential) speeder.

[gremlin]

normally if you go down a tooth on the front, your speedo (if taken from the gearbox) will "over read", if the speedo is taken from the wheels (m600 750 ) then it wont make any difference. i dont know what a 900 has

Mr G

[Nickj]

There are two clock types, one mechanical which drives off of the front wheel and the electronic which feeds of the back wheel.
The only way you'd change the speed readings would be to increae or decrease the wheel size. To under read speed you'd need to have fitted a bigger wheel either front or back depending on the pick up type.
And before you ask, no the tyres shouldn't make a significant difference unless you have a really bizarre size fitted
...... So in either case it's the clock itself that's not right.

The mechanical ones you can get recalibrated, the electronic ones would need the dial start position set back to compensate so that 0 is actually 0 again.
In either case the speed difference ought to be linear so careful as at an indicated 40 you'll be doing nearly 45!!

[Pedro]

It may be that the speedo drive on the front wheel (assuming it's driven from the front wheel) has the wrong gearing in it - from memory there are a ouple of different ones depending on the bike - 888s have a different one to the Monsters I believe although they look identical

[BluprintZ]

It may be that the speedo drive on the front wheel (assuming it's driven from the front wheel) has the wrong gearing in it -

Cheers guys.
My speedo is driven from the front wheel, so i doubt changing the sprocket has made much difference to the problem?
The bike had 10k on it when i bought it in April, deffo a Sunday bike.
I've been through all the paperwork i got with the bike, service history, reciepts for parts, etc.
There's nothing in there that points to anything speedo or drive parts being replaced, although obviously it's quite possible that one of the other two previous owners could have had repairs done to the drive.
If so, then i expect it's not beyond the realms of possiblility that the wrong part could have been fitted?
I have been in the odd situation whilst i've owned the bike, where the dreaded "arrive alive" candid camera van has suddenly been there when coming out of a corner and i've had to jab the brakes a touch to get it down to the right speed, although as yet, i haven't had any probs with being snapped, so i suppose the speedo should be somewhere near right, otherwise i would have been serving a ban by now.
I dunno, strange one!

[singletrack]

Perhaps you could borrow a sat nav from someone. If it has a spped reading that might give you a good idea of your real speed.

Or was that guy really dreaming his Harley was doing 97?

[BluprintZ]

Perhaps you could borrow a sat nav from someone. If it has a speed reading that might give you a good idea of your real speed.
Or was that guy really dreaming his Harley was doing 97?

Now, now missus, let's not diss the more unfortunate of our Vtwin cousins!
The guy knows his stuff where engine performance is concerned, i've known him for over 20 yrs, his bike is no slouch..
The sat-nav suggestion is a good one, certainly food for thought, we'll see.

Did anyone notice the the fact that in my first post on this page, the word "s******ing" had been censored?
C`mon Ped, or whoever decided that a word for laughing (as young lads at the back of the class would do), was worthy of censorship, lets not get too pc eh?

Thanks all.

[Capo]

Now, now missus, let's not diss the more unfortunate of our Vtwin cousins!
The guy knows his stuff where engine performance is concerned, i've known him for over 20 yrs, his bike is no slouch..
The sat-nav suggestion is a good one, certainly food for thought, we'll see.

Did anyone notice the the fact that in my first post on this page, the word "s******ing" had been censored?
C`mon Ped, or whoever decided that a word for laughing (as young lads at the back of the class would do), was worthy of censorship, lets not get too pc eh?

Thanks all.

The censoring software is stupid. It operates on a text string regardless if the string is embedded within other characters (thus adopting an completly different context and meaning).
In this case I believe the sensored word has something to do with the colour of ones skin.

[sbhumphrey]

Can I ask, did you lose much off the top end with the 14t sprocket fitted?

[utopia]

...... the word "s******ing" had been censored?

I believe a certain north-east seaside town beginning with S and ending in Thorp had its name censored recently too.

My experience of those sorts of speeds on a naked monster suggests that 97mph would be verifiable by the fact that its a definite effort to resist the wind-blast at that speed, wheras 80mph is just about ok.

[BluprintZ]

Can I ask, did you lose much off the top end with the 14t sprocket fitted?

Wow, this is an old thread but in answer to your question Humphrey, yes i think it did.
It seemed to be revving it nuts off at 80mph, although it got there pretty quick and it was deffinately less lumpy in town traffic but, i couldn't handle the thought of the engine revving harder than i liked, so i replaced the 15T and it was back to cruising at 80mph.
It's all down to a matter of choice and riding styles.

G ; )

[jerry]

A few months ago I was accused by a traffic police officer of doing 138mph on my M750 which maxed out could only ever do 125mph ...turned out his radar unit was faulty. I reckon that at the time i probably was doing 90mph so his unit was over 40% out on its readings .