piston feed back

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Jul 8, 2006
Im just woundering if any ones running GPM pistons from norvil.
Im running hyperlight pistons at the monent and looking for feed back on cheaper and easier to get GPM.

thanks joe.
I was informed quite recently by a UK Norton parts supplier that the GPM manufactured pistons are now the type generally supplied as genuine parts by Andover Norton, as the company (Federal Mogul) that supplied AE Hepolite pistons (I guess you meant Hepolite Joe?) will only supply in batches of 5000 (of each size I believe?) so I would expect the GPM type to be a good quality although I haven't used any myself yet.

There are still supplies of Hepolite pistons available although I expect they could become harder to get hold of in the future.
I've used GPMs in my 750 without problem, but did find that they really need ring compressors to fit.

I've never had difficulty fitting Hepolites by hand but the GPMs have a cast oil scraper ring in place of the three-piece spring favoured by Hepolite and they can break during assembly even if you think you're being careful :oops:
I'm using GPM pistons in my 750. They came to me from Andover Norton via OldBritts. 1,000 miles on the engine now and no problems. No smoke, no oil consumption, runs good!

Those stupid oil rings did make it difficult to install the pistons into the cylinders though. Next time I'd be inclined to look for NOS Hepolites with the three-piece oil rings.

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