Mr Tyler!!!!!
....that is why the 470 is known as the ratfuck engine........you just about gold leaf plated the term there all on your own!
not quite sure I've ever heard the term "I've blown it up twice in a week" before. maybe we're a little loose with the 'actualitae' there but I like your style...got a tale to tell; so tell it!
the problem is, nobody knows which piston is in them. a photo of the crown would help, I can tell by the codes printed in them.
as for 'just' rings, what happened to this bike? you shouldn't ever need 'just rings' because the piston always goes before the rings do. forget what your father teaches you..... fact is, that with todays modern short skirt pistons in short-stroke engines; the piston only has to show 0.02mm of wear, the piston rocks, the rings can't seal and the bike becomes a smoke machine.
if it needs re-lining it needs a piston. if it needs a piston, you have a chance to change the shape of the piston and (I suggest) LOWER the compression while getting the squish band right. you would have the same power but the engine will feel softer and last longer.
before stripping, its vital that you measure the gap between the piston and the head at TDC with the HG fitted. a bit of plasticine is all you need and inpregnate it with 1mm solder wire looped like an ampisand "&" and placed at 3 and 9 o clock - so over the "wrist" (real name gudgeon) pin ends - and smeared in a little oil. rock it over TDC, take out the solder, measure with a very-near caliper and then the next piston can be selected.
Taffy
