my 604 is more or less just sitting and you are more than welcome to come over and spend a couple of hours going over it to help you with the process of doing yours i dont think there are 2 the same when it comes to the 604 /640 variant
and is often the topic of a ruck in my house you dont use it enough Bla Bla Bla
I have seen a lot of posts on carbs and jets but not to many on Dyno results
mine was putting out 70lbs of tourque at the wheel and something like 46 BHP but that is off the top of my head.
it has been set up to run in the 12-14 fuel to air ratio through the range and is returning something in the range of 45mpg this dose go up to 50 when you cruse at 60mph ish
so refuel is about 110mile range
I have a crank case with the top hats still in it so you are welcome to them i will just need to drift them out
I will say if I was to do it all again I would build a 500 version
so if anyone has the cash sitting for a concourse 604
I may well do it
you will also be able to drop your exhaust
Im not back from China until next week i will PM you my number