Roelof, i hope this doesnt turn out weird or sound strange, but every time you mention putting solder in to check the head clearance, for some reason I have a giggle about it! Not in the way that I think it's silly or a dumb idea, but just a funny feeling - I don't know, just thought I'd let you know
Originally Posted by
beebone
Yes, those are same stroke, both using R7 conrod.
For sure I will use Kangaroo crank (14mm) because the conrod pin on crank worn out, so the glow plug on F 21 burnt always. So give it a try to move the 9 ports P/S to Kangaroo.
It doesn't matter what length the rod is, the stroke won't change. If the crank has a larger rotation path, then the stroke will change (not sure if that makes sense) What Im trying to say is if the distance from the crank pin to the center of the crank (on the Flash) is further than what it is on the Kangaroo, the stroke will change, and with that it will perform differently. I dont think this will happen, as according to the Novarossi site (comparing the Flash 21 Special, and the Syd Kangaroo) they have the same stroke.
Just like Roelof said, see if the piston sits (at its lowest point) right on the bottom of the exhaust port. If it doesnt sit exactly flush, it's not a real problem, but it will perform differently (could be better than stock) and you should check the head clearance as well.