hiya just wonderd if i changed the front sprocket would my speedo still be right ?
No, it’ll be slightly out, reading faster than you’re really going. But it’s only by a very small amount, a friend and I have checked whilst riding side-by-side, it’s hardly noticable.
At Seastar superbike the technician told me that if you have -1+1 on your bike it will give you a difference of 7 to 10% less than the real speed on your clock 
. Meaning if you read 100mph it will be 90mph.
Went -1 up front on mine and it was 10% out, but buying a speedo healer will sort that
i think thats the way to go then …cheers guys