Originally Posted by JMo

That's a comprehensive report, thanks Ray (I had my tank up the other day too, it's a bit of a fiddle as you say - I can see the price to check/adjust the valves being pretty high labour wise...)

As a thought - Presumably the speedo reads off the gearbox output shaft? - hence the smaller front sprocket spinning faster shows a higher top speed right?

Now correct me if I'm wrong (I'm no mathematician) but you kept the 15T front and you put a larger rear sprocket on instead (say 47 teeth), the rear wheel is now effectively turning slower for the same engine revolutions? - would than not correct the speedo over-reading?

If so, perhaps this is the problem - that the bike actually ought to be running slightly lower gearing (that is using a larger rear sprocket), but they put on a 45 tooth in an effort to keep the revs down at speed and improving MPG?

I'm going to try it next time I fit a new chain and sprockets...

xxx