what is the ratio for fj1100 speedo?

[Goetz]

Id like to mount an aftermarket mechanical speedo, anyone done this or know the ratio?

[Arnie]

I've used "bicycle computers" on motorcycles before. 
These typically give speed, distance, distance since reset, and most importantly TIME. 
Some have additional readouts. Basic units can be found for $15 or less.
These have a small magnet that attaches to the wheel or brake disk and a pickup opposite on the fork leg, brake caliper.  Then you set the circumference of the wheel into the unit.
I've found them to be very accurate once set correctly.

Arnie

[Goetz]

Do you remember the make or model of comp?

[andyb]

Sigma is one that oft is reviewed well. 

Someplace on here I thought someone posted what the ratio was on a speedo.  Can't find it at the moment, though.

[Arnie]

The one on my (for sale) Cagiva Navigator is a Sigma BC800

About the only thing you need to be wary of is that some bike speedos have a top speed limit.
I don't know why. Its great to see 100kph or more on a downhill run when all tucked in on a bicycle :-)

Cheers,
Arnie

[Goetz]

www.ebay.com/itm/New-SD-548B-Bike-Bicycle-Cycling-Computer-LCD-Odometer-Speedometer-Black-and-Red-/120956032873?forcev4exp=true&forceRpt=true#ht_6747wt_1174
Just ordered this, cheap and free shipping, low risk purchase. The only issue i see is mounting the magnet. Designed to clamp onto a spoke, how will i mount it? We will see

[Goetz]

I also just ordered some slim, crazy strong neodymium magnets.