To be fair the speedo dont seem that far out, use a sat nav to get true speed, at 50 speedo is showing apx 55, but the needle is all over the place anyway....
Take off the speedo cable, pull out the inner drive cable, spray some WD-40 into the top end of the outer to wash it a little, shake off the excess, wipe and wash with WD-40 the inner drive clean, apply a little engine oil or similar (NOT TOO MUCH!), and refit it. 99% sure to cause speedo to run steady.
Any diagrams floating about on timing etc?
See my posts today about doing timing!
CharlesY