Hi
PhilI am no Villiers carby expert.
I wish I had an answer.

i dont know if its a 70cc or 98cc
is there an easy way to pick the difference
There is an easy trick I have learnt - provided we have cylinder evidence...
70cc engines have cylinder cooling fins at 90 degree around the spark plug.
98cc engines do not.
Please keep us informed as to progress.
I feel you are assisting folks in a similar situation.
Cheers--------------------
Jack