Hi Keith,
Did a bit of research, on suitable fan sizes that would suit the standard KE radiator, but the answer was right under my nose.
I bought my daughter a 2004 Echo last year, & I went out and measured it's radiator & fan up this morning, & it is almost perfect. It's outside frame couling/shroud, is within a cm of the KE radiator core dimensions, in both directions.
If anyone has utilised an Echo fan on a KE sucessfully, please give me a yell.
I will get hold of one, & adapt it, using a spare radiator I have in the shed, then pop it in one weekend.
On paper, it should be an easy & clean swap.
I'll post a pic on here, when it is done, after which I'll do some temperature data logging exercises, with multiple temp points, to see exactly how well it performs.
Cheers Banjo