speedometer advice

[kaiser]

hi all
i am looking for a replacement speedo for my 1991 100gs and have found several on the german ebay however they have a diferrent 'w' rating of 715 whereas mine is w1148 i know this is something to do with the gearing,so the numbers must match but is this diference just due to the german one being in km/h . i alo found one on motobins for an r 80 which had a w of 1190 and was told it would not work corectly on my bike .any advice would be much aprecieted ,its all a bit confusing

 

[VAL. H.]

hi all
i am looking for a replacement speedo for my 1991 100gs and have found several on the german ebay however they have a diferrent 'w' rating of 715 whereas mine is w1148 i know this is something to do with the gearing,so the numbers must match but is this diference just due to the german one being in km/h . i alo found one on motobins for an r 80 which had a w of 1190 and was told it would not work corectly on my bike .any advice would be much aprecieted ,its all a bit confusing

Oh! This is interesting, I was going to start looking for a smaller speedo to fit with the headlight mods I'm planning.

Guess I'll whatch this for a bit.

Val.

 

[frank1200]

from what i can remember from my tachagraph fitting days, W also known as the k factor is the number of times the speedo drive in the gearbox turns over a set distance
this is affected by the size of rims and tyres and final drive ratio
if you change any of the above your speedo will be unaccurate
so to answer your question the different speedo might work but the readings could be all over the place
unless 1 W is over a km and the other over a mile them they mightr be similar

 

[mikyh]

Ditched it altogether

As all know, the speedo of GS's is shit. breaks down in 20-30 thou Km.
So I put a TrailTech thingy, 100$ plus postage.
It works realy nice, with back lighting and lots of info.

You can see mine here:
http://picasaweb.google.com/balabutiro/MikySGS#5311165287971417954

And the site:
http://www.trailtech.net/

Miky

 

[Thunder]

Frank's covered the reasons pretty well, its all down to the ratios of wheels tyres and the final speedo drives.

I changed the speedo on my 80 mono to MPH and the replacement is marked W1244 while an original km/h version is W747.

If you don't have the correct ratios it will be inaccurate.

 

[John Armstrong]

If you don't have the correct ratios it will be inaccurate.

And if you do it won't be much better

I run with my GPS on all the time so I know what an actual 30mph is

 

[Redboots]

I run with my GPS on all the time so I know what an actual 30mph is

You are a brave man if you run through a speed trap, relying on a GPS readout
Best accuracy you can get is about 5 mtrs.
All the other accuracy figures touted are for mountain top/ideal weather and 11 satellites "in view" reception.

John

 

[Trippy]

I needed a speedo for the Basic, I had the choice of £180 for new or £20 for one that was a different rating. I went for the £20 one and checked against my GPS its 6mph out. I can live with that.

 

[John Armstrong]

You are a brave man if you run through a speed trap, relying on a GPS readout
Best accuracy you can get is about 5 mtrs.
All the other accuracy figures touted are for mountain top/ideal weather and 11 satellites "in view" reception.

John

Rate of change so as long as the satellites are reasonable, then the GPS figure will be reasonably accurate

Just out of interest, what does your speedo read at a true 30mph?

 

[kaiser]

thanks for the help maybe i need to get a trailtech one then, i am just worried it willo be another temptation for an opertunist thief ! im just wondering if the w715 km one is correct as 715x1.6 (1.6=km to miles) is 1144
so this should match up maybe

 

[Redboots]

Just out of interest, what does your speedo read at a true 30mph?

Bike in bits
Bit buggered as mine is in kph, but I try it in the car and let you know.

John

 

[John Armstrong]

Mines "slightly" optomistic, but the error remains roughly constant in mph terms


And some links with some relevance to the original post:

http://www.airheads.org/content/view/222/49/

http://www.bmbikes.co.uk/specpages/R100GS.htm

 

[(RIP) pastyman]

thanks for the help maybe i need to get a trailtech one then, i am just worried it willo be another temptation for an opertunist thief ! im just wondering if the w715 km one is correct as 715x1.6 (1.6=km to miles) is 1144
so this should match up maybe

Ive also gone for a trailtech.. £78 squid, IIRC, easy to fit and can be made as accurate as you like.It can be bolted to the bike so no more vunerable than any other. gives revs, speed time dist average speed and air or engine temp.
all in all not bad at that price. depends on how much originality you want,