Ariel Owners Motorcycle Club

Alloy cylinders expand rather more than iron so less clearance is required, about .001" per inch of bore.
"it is a great aid to assembly to make gudgeon pins an easy hand-push fit when cold. ... In any case a 3/4" pin will have about .002" clearance at running temperature, another 1/2 thou will make very little difference" Phil Irving in Tuning for Speed 2nd ed.
I have always found that hard to believe but have never done the calculations to ascertain the truth.

Pistons for Ariels?
For VH/VG singles Club pistons (specially commissioned from IMD) have been available for a while now, available to Club members only (see the magazine). (Should probably have put in an update about these before now - see also other Forum topics....)
Weight (for a +020)(with rings, no pin or circlips) 359g, pin (internal taper) 99g

Also, JP seem to be updating their catalogue fairly frequently (the website is on their 'international product information email list' ). Currently it's possible to find their Ariel range on their website (enter Ariel in the search box):
https://www.norndaautomotive.com.au/jp-pistons.html

There is differing comment about how the JP pistons actually perform; the manufacturing process might have been amended for the VH pistons but unfortunately there is no information that I can find on how to recognise one of the 'new type' from one of the 'old type'. However, JP are currently listing a much wider range of Ariel pistons than just the VH/VG pattern.

SG

The New ones resemble the earlier ones only remotely. I've seen them and they look equal to the Best with an accuratetely dimensioned steel 3 Piece die used giving strength and Minimum weight . The A$ is only 48 UK Pence and they will build to your spec so worth visiting the site. They will also machine finish to suit your bore Individual size so avoids boring out more metal than absolutely necessary. . Nev