Oversize pistons for an 88

Probably need to measure the wear . I have re-ringed some used pistons with later better oil rings and it has worked well.

The Gandini and JP pistons are quite good as replacements. Anything new with Hepolite on the box, unless genuine New Old Stock, is likely to be a poorly manufactured copy from East Asia.
The drawback of JP and Gandini is the weight penalty they come with. These pistons often weigh up to 50g more than genuine original Hepolites. Resulting most likely in a need for a crankshaft rebalance.

I'm going through a similar experience with my 88. New to me last year and bought from auction with no history. 

ive had the same issues of oil burning and apparent heavy breathing and decided to strip the engine down. Mine was on 20 thou over and the bores were a bit glazed and had previously been honed with sandpaper over some scratches/slight gouges in the bores that you can still feel with a finger nail. It was also very clearly blowing at the head gasket in every direction. This was due to the top of the barrels being far from flat.

I decided to give the barrels a complete freshen up - tidy up the top mating surface and re bore for new pistons. I spoke to the machinist/engine builder/tuner I use and ordered the next size up pistons from Gandini (+40). 

i dropped the parts off with him over Christmas and when he looked at it he suggested fitting liners to go back to standard bore as this would allow the spigots to be removed for machining the mating surface. I pointed out that there are a number of posts and bits of info that suggest it's ok to skim the spigots off and run without them. He had a measure up and concluded that the top ring would come out of the bore slightly if this was done so it looks like new liners and standard size pistons are the right option for mine.

anyway - I think what I'm trying to say is it might pay to show the parts to the machinist/engine builder before deciding what to do (unless you do it yourself of course).

I've weighed the original pistons (20 over) and the 40 over Gandinis. The gandinis are lighter by 30g

The Hepolite name is owned by Wassel now. All the new hepolites i,ve come across and fitted are made by JCC in Taiwan and are a very good piston. In my opinion they are better than the original hepolites. Plus they are a ton cheaper than the JP or Gandini   

JCC pistons, made in Taiwan are (or have been) sold as JCC, EMGO, Hepolite, Harris and at least one other brand that I can't remember.

As Peter says, they have gained a good reputation for quality and consistency.

I had heard (internet) doubts about some of the rings and circlips that suppliers boxed these pistons up with, but not recently.  It's hard to be sure what's what, because ring problems are often caused by the fitter or the borer.

It's just occurred to me that you're looking for a decent piston to go to from the current +30 size and I probably need to change mine back to standard. I've emailed Andover to see if they will take my +40 Gandinis back (boxes have been opened) but no reply yet. Yours for 10% less than what I paid if you're interested?
weight is approx 290g including rings, pin and circlips.

I`ve been doing my 88 over the last year and was quite new and lost to the Norton engines. I had the Gandini pistons as advised by my Reborer . I did find that they needed some work to match there weight though. 

Also worth checking the valve guides. It is not uncommon for them to be loose in the head which also is a source of smoking.
Paul

Certainly worth checking valve stem clearance and possible loose valve guide.  Valve guide hole in head can be damaged if an old guide is driven out cold and/or with carbon on it.  Then oil gets sucked down the inlet...

You could go one oversize bigger and fit 650 pistons. I have done that in the past.