Engine!

Hi guys, can anyone help me with some advice?
Want to get a big bore kit for my 1973 6volt st 70.
Want a good quality Japanese one, which will last, what are my options?
Spoken to monkeybike uk, they seem to make it complicated!
88 cc will be fine, but would even go of a nos Honda 70 if there is such a thing...
But I do need a new cylinder head...cheers.

My suggestion...
get a 85cc kit (51mm) wich will fit right in.
DRP makes good and affordable kits.
Quality wise: Kitaco or Takegawa,...

Same for the head or a nice (rebuilt) Honda OT70 head.

It's adviced to upgrade the oil pump as well.
Maybe a stronger clutch (or at least a renewal of the plates) can be necessary as well.

I have a very nice set here which can be sold for the right offer...
Have two of them... and 1 is enough.