Old as the hills question? (C90 engine fitting?)

I'm new here so forgive me for asking a Q that has no ndoubt nbeen asked before:

6V C90 engine in 1971 ST70 frame (or CF70, got 3 of those!).
Told one 1 site that 6V engine with points on head/cam will not fit but 6V 90 with points behind rotor will.
I've now read that no 6V 90cc engine will fit anything else other than a C90 6V frame.
I have such an engine and a 71 model ST' and 3 CF70's This engine not fit without some work?

No, a C90 engine is not plug and play.
The only 90cc's (88cc actually) are the Jingcheng DX90 and the Honda CD90, S90, CL90
(not 100% sure if all versions will fit perfectly).

The C90 engines are called "big harry" engines.
They are a lot wider on the clutch side, and the engine mounts are somewhat different.
http://specificdesign.com/honda.htm


Concerning your question about the cases, yes, 50's and 70's versions are almost all exactly the same.
There are some differences in the different types: CF, ST, C, z50a, z50j,..... regarding
different types of cranks, bearings, distribution,...


PS:
- Technical question removed from "sales" section.
- Please choose a clear title, to make futur searches easier
- Welcome!!!

Thanks for the reply and the welcome mate. A shame the engine will not fit though! My bike's a standard 1971 ST70 and does 40mph on a flat road, guess if I want to go faster I'll have to get one of my other bikes out !

Magic tip: tune your engine!

First of all, get your hands on an engine suited for fast ignitions: ST50 (not all), z50, cf70, ss50, c70,...
Fit a 85cc with a good cilinder head, and you'll find yourself 'flying' at 50-60mph, with a 100% original looking engine!