Modern Vespa

Hi all

I've recently setup a Koso DR-2 speedo to my scooter (better functionality than the SIP one) and also used the speedo drive convertor that bolts into the normal spot with the worm drive on the forks (I've a PX disc fork).

Some links are:

Koso DR-2 - https://kosonorthamerica.com/product/db-02r-lcd-meter-street-version/

Convertor - https://www.scooter-center.com/en/speed-sensor-digital-speedo-cable-koso-d-jis-type-a-koso-d-jis-typ-a-vespa-vba-vbb-gl150-gs150-sprint-gt-gtr-super-ts125-rally-lambretta-dl/gp-li-sx-tv-black-plug-kobf580000

I'm getting a signal though the speed seems to be displaying about 30% too high (so say 80kmh when it feels like I'm doing 60 kmh).

There doesn't seem to be a setting to say you're using this setup, just the option to enter the tire circumference and the number of triggers per revolution.

I entered 1330mm and 1.

Before I get into a bunch of testing I thought I'd check if anyone has experienced this and/or knows the values to use to get it to work?

Cheers

- Matt

I've just found a copy of the SIP speedo manual and found a reference to using the shaft drive sensor (see attached) and compensating for the worm drive gear ratio.

So it seems as I've a PX fork I'm looking for a transmission ratio of 0.75 (which feels about right).

So given my wheel circumference is 1330mm and the ratio is 0.75 I need to change the wheel circumference setting to 997.5mm (1330mm x 0.75) to correct the speed display?

Does this logic sound right?