My NH 350 Piston

[SyeButts]

Good evening all I was wondering if any of you know the make of my piston and if they are any good? I stripped my engine as I have only just bought the bits (wasn't a complete bike but plenty to be getting on with) to see what sort of state the internals were in and when I removed the piston it was nothing like I had ever seen before. I used to be the manager of a famous classic scooter shop dealing in Lambrettas and Vespas which had been fitted with every 2T piston imaginable (especially when it came to later Indian imports straight off the streets) But I have never seen one with big slits on the skirts like that. None of my 4T bikes had them so I was wondering what make they could be and because it is in such good nick are they any good to use or is it old tech that has now been improved. The piston has the STD stamp so not oversized and it seems a shame to not just get some new rings for it and re use. I hope all that made sense. Any help would be greatly appreciated. Thanks

[will_curry]

Welcome to the forum.

I wouldn't expect the piston from an NH to look anything like the piston from a two-stroke and the
slots you describe sound like those of the split-skirt pistons fitted to some NHs.

It would help if you could post a picture of your piston.

viewtopic.php?t=193 is the topic on this forum to guide you
in how to post images.

[Roger Gwynn]

What markings are inside the piston, it is unusual to not find a makers name or reference. I suspect, as Will says that it is a split skirt piston.

[SyeButts]

Cheers Roger and Will for the reply I will have a look for makers mark later and see if I can upload a pic.

[nevhunter]

I used to know the Bloke who made all the ACL pistons here in Aus and from all he told me, I reckon those slotted pistons are weaker and only suit water cooled motors where the cylinder never get that Hot Hepolite made that type as well but they were sold as a touring piston (whatever that is) The crown and rings run very hot in that type and the are known to crack as distortion is part of the deal. I prefer the full.skirt solid type used in the W/NG with a suitable clearance and not a lot of ovality. More heat gets out of that type than a slipper or very oval piston. Nev

[SyeButts]

Thanks for that bit of info Nev. No pics yet but i can tell you the piston is a Heplex the pat number is 616 820, has AM 413 and 12745 in the inside of the skirt, std stamped on domed crown and a dimple above the half moon each side. It looks in quite good nick for the age. Hope that helps. Thanks again all

[SyeButts]

Found it now its one of these https://draganfly.co.uk/shop/56842/pist ... #12745/STD so what do you Gents think new rings or whole new kit?

[charles.bulloch]

Have you checked the ring gap, it may not need new rings?

[SyeButts]

Have you checked the ring gap, it may not need new rings?

Not yet I am giving the barrel and bore a clean today then I will.

[nevhunter]

Sye, that's the type I don't like. If your current piston is OK and the top ring groove is not worn and no ridge at the top of the bore consider just re ringing it. Nev