Speedo accuracy

[petemillis]

Right, when I drove the RX7 back from the docks on Thursday the speedo needle was banging off the end of the scale at 5000 in 5th (so obviously already delimited). Fitted speedo chip today and the speedo seems accurate enought up to about 60mph  I guess but when I get to 3000rpm in 5th it says 90mph (should be about 75?) Apparently I was doing 1**mph down the A23 but I know it can\'t have been much over 90mph. It\'s definitely not a problem with the speedo converter as the distance shown on the ODO is spot on for the round trip I just did to the MOT station and back (where I\'m pleased to say it sailed through).
Are there any known problems with the speedo unit itself (you know the dial)?
Cheers

[petemillis]

Has nobody had a speedo on an RX7 that seems normal to about 70 mph then seems to vary between 90 and 100 at 3000rpm and then when you go to about 5000rpm in 5th is indicating some speed it can\'t possibly be???
I\'d just like to know if I\'m the only one with a speedo like this and what could possible be causing it. Like I said, the distances on the ODO are reading correctly (verified over a return trip that I know well). Wassup?
Cheers

[petemillis]

Sorry to boot this to the top again. Speedo working fine today till I stopped to fill up with fuel. Restarted car, sped off along the A27 and it went all queer on me again like saying 100 at 3000rpm in 5th  and 160 when I went a bit faster (5500 rpm) - oops, forgot I\'ve got reg plates on now!
As it work ok, then didn\'t, I guess this sound like a dodgy connection somewhere. I\'ve already removed and refitted the connector on back of dash panel when I fitted the speedo chip. Anyone know where the speedo sender is??? Wish I had a wiring diagram....