Spider speedo question...

[Alfa Romeo Search and Rescue Society <alfabill@domain.elided>]

Ok gurus, here's an easy one for you.

I rescued a Spider, 86 model, and the Speedo, after replacing the cable
with oem, will only register to 40 mph.

New owner would like it to go higher, and pressing the gas doesn't help
;o)

Any ideas what would cause / cure this? 

Thanks 
AlfaBill

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