+30" Jubilee pistons

Have you considered getting your old pistons ceramic or similar coated on the skirt to restore them. As long as your ring slots and gudgeon pin holes as good then it should be possible to clean up the OD and get the coating to bring it back to size.

Norton supplier on big twins

https://jsmotorsport.com/product/piston-skirt-coating/

.. to match them with alternatives eg from JP pistons? They don't list the Jubilee but they have a catalogue that you may be able to search for something suitable.

https://www.norndaautomotive.com.au/jp-pistons.html

Or how about a Honda C77/CS77 on this list? Correct bore.....

https://4-stroke.net/library/honda-piston-size-chart

If you could go to 61 mm (.040 overbore) there are loads on the list to sort through.....

JP pistons process is to make a larger range of pistons from as few blanks as possible, most end up a lot heavier than the originals. Add in their useless rings which may never bed in and their habit of leaving off a machining operation, they are best used as an absolute last resort.

... may well be true but (a) I was suggesting finding another piston that may fit - not necessarily from JP - and (b) better a bad pair of pistons than a useless ornament in the garage.

I was only referencing JP from bitter experience of finding all the noted faults twice thankfully not on my rebuilds but where I was asked to sort the issues out. I made no mention of your other suggestions so not sure why you thought I dissed any suggestion other than JP.

Here’s one to get you started! 

https://www.ebay.com/itm/265426747736?ff3=2&toolid=10044&campid=5338249078&customid=hepolite+pistons+Norton&lgeo=1&vectorid=229508&item=265426747736&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&ufes_redirect=true

Hi Kev,

It's surprising how difficult it is to get some parts for Norton Lightweights. Not long ago everyone re-bored their bike almost as routine whenever the barrels were off. Good for Hepworth and Grandage in Bradford and all the Norton dealers. I can confirm that Hepworth and Grandage are now levelled (Morrisons I think) and the Hepolite piston supply  is well and truly turned off. When the pipeline runs out.......... just as you found out.

Truly, how much are you going to ride this bike? If it slaps a bit when cold are you going to notice above the rest of the noises? If it burns a bit of oil, do you really mind?

Did you get the piston on e-bay spotted by Dan?

I've searched all over on your behalf and can't find another.

I hope it's obvious which way to go. Like it or not.

Peter

Sorry, Kev - public apology....

We did talk about this at Norton Day - but sadly I have been a bit involved in a house selling/buying nightmare. Don't let anyone tell you that this the most stressful thing you will do in your life. They are all wrong - its more than twice as stressful as that! Esp when your Solicitor goes missing on Completion day..........

I do not think I have +30 Jubilee pistons after all.

If you have existing pistons, you could/should try cleaning them up. Better a bit of piston slap when cold, then seizing when hot. Back in the day, engineering companies discovered that Jubilees re-bored as per the book could very easily seize up, due to the deeply spigotted barrels and poor heat dissipation. So an experienced engineering shop would add a thou or two to the dimensions, giving that bit of extra piston to cylinder clearance.

... the light use that most older bikes are subject to I always have rebores a couple of thou bigger than the book value. It saves all (or most of) that tedious running in, and piston slap with that much clearance won't be too bad. Edgar Franks suggested a rebore on my ES2 when the wear was more than .007".....

You could advertise for a SH + 30 piston   and fit with new rings  etc.

My ES2 with a bore about .002" bigger than standard doesn't actually make an appreciable noise and burns no oil whatsoever. It does however run like a top and accelerates in a very satisfying way. But you are of course entitled to do whatever you wish. I'd rather have a running bike than an ornament in the garage however "correct".

https://www.youtube.com/watch?v=y6IMRXgZE8k

https://www.youtube.com/watch?v=31FqpkF2PK0

Nice looking bike, Kev.

Unusual to see Roadholder forks on a Jubilee.

The great advantage of a Jubilee is that the barrels can be removed individually.

You can run with one new piston and one older piston.

Then, when the next new + 030 piston turns up, pop it in.

Better make a written note of which side you put the new piston. It may be a while.

Peter

Hope to see you on this bike next year. Cut your own trail at your own speed. If the rest find it a bit slow - they need to learn respect.

Yuk !  Slotted pistons  ,one with easily detachable top.   Know a good man  at alloy welding?  

Those additional slots are to help with oil cooling and when the tops come adrift you get air cooling as an extra for free.

Kevin.......Checkout BSA, Hampton, Heinkel, Honda & Jaguar who all used 60mm pistons in their vehicles and appear to be available in other sizes via JP Pistons. You might need to donate an arm and both legs.

As a far fetched alternative .....dial into AliExpress who can connect you with suppliers of 60mm, 61mm & 62mm bore pistons for 4 stroke bike engines. The prices are very low, bordering on silly but I guess you might get what you pay for.

Are the numbers below reasonably close?

Norton - 249cc OHV (Jubilee 250) Year: 1959-66,

compression ratio 8.75:1 (bore 60mm)   (in your case a bit more for +30" pistons) 

compression height 1 11/16,

piston length 2  1/2 -  (flat top with valve pockets)

Pin diameter  11/16.

Get Anna to weld up the slots !!.

Robert,

Perhaps a slot was intended and seen as an improvement. More oil on the bores?

My Jubilee piston, with AE logo (Associated Engineering who owned Hepworth and Grandage in the 50's and 60's) has a slot too. Photos attached.

Definitely a story to come from our Lightweight expert on piston lubrication problems for Jubilee. I confirm from first hand experience the Navigator piston crown can separate from the rest of the piston with sufficient abuse.

And the Electra piston design is completely different and much sounder.

Peter

 I was in jest , however  in the absense of  any acceptable replacements ??.  My 99 pistons survived a seize up  with slots , but I was more than happy to fit non slotted 650 pistons . I once heard of someone selling a running bike  with a pot patch on the piston crown ,and wood pistons have appeared !.   Early 250 pistons cracked from the slots to the pins.  As Phil said there must be a solution out there.