First post for me, and its a mechanical issue !!!! Not a good start

I have read all the posts i could find re the dreaded "rectum frier" so many that i have in fact just bought an R1 one off ebay.
Anyway heres the prob : Bike has always been a good starter until now and when you hit the starter button it whirrs away without starting and then just as it sounds like the battery is about to give up it starts to fire up and then it roars into life with the usual roar through my ART cans and all is well BIG SMILE

I have checked the starter and all is well, battery seems ok, charged it and checked it as best i know how with the old leccy tester.
Plugs have been changed also but after this symptom started as a way of a potential fix.
Will be changing the rectifier for the R1 one as per forum mod instructions (thanks whoever posted that)
So to cut it short, if after i change the "rectum cooker" this persists any ideas ?
I am panicking now that it may turn out to be mechanical rather than electrical.

Any feed back will be greatly appreciated.