xj750 seca speedo is out

I have done a speedo swap on my 82 xj750 rj seca from the 80mph/120kph speedo to a 220kph speedo and I find that the speedo is out. When I am traveling at 110kph it is only showing about 90kph on the speedo. I had to make 1 out of two using the new used speedo in my old body , and I am still using the same speedo drive, any idea on what is causing the problem? thanks.

 

could be dirty and needs cleaning and light lube lube cable to.
what bike did the new higher kph speedo come from?

could be the magnet is weak if you put a strong magnet on it for a while it will help bring it back from what i have read on this site
Speedo and Tach dissection with pics

 

The drive unit maybe different

 

or tire size from donor bike.
do not know if the drive can be swapped out

 

I'll add that I have nothing to add.

I have the same problem. I'm waiting until the winter to tear into it

 

everything is stock ,it seems they used different speedos on different models, I don't know what years/countries but mine had a 80mph/120kph speedo that wasn't working, but after my spill which smashed the cover, I sourced a complete 220kph cluster from western Australia, but unfortunately it had some wiring cut so I used the working 220 speedo in my cluster with the new cover. I have tried looking to see if speedo drives from different years have different part no's as I am thinking that is the only thing it could be. The higher kph speed0 unit came from an 82 xj750rj same model as mine