What are the best 850 pistons ?

Frankie17 said:

Eddie i am not the one getting snotty hi Frankie 17 ( whoever you are ) not the most diplomatic response to my post

JCC pistons are supplied by multiple vendors under many brands Cycle craft / Emgo / Hepolite / and of course JCC there may be more

most Distributors choose to supply optional brands of Rings with the pistons Grant / JCC / Heplex / Hastings / total seal / NOS many dealers have their own favourite
brand of ring set ( depending on availability ) they pair these to the JCC pistons they use in their own workshop or sell over the counter

So this question is all based personal choice and what is commercially available at the time , most traders / engine builders will always have a vested interest in supplying their own product line
and will not endorse an alternative even though it is often the same combination of piston ring at a lower cost

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Ahhh, sorry about that, I can see how that may have irked you. That’s my bad intonation. I intended to convey that you seem to be quite well informed and perhaps mildly defensive, as if you perhaps sold them as you were in the trade yourself ! If you are, and you’re confident your pistons / ring / clip sets are good, please tell us !

So it’s kinda like Kommando said, it’s pot luck as to what rings and clips you might get in the box. Sadly though, if that’s the case and you’re a layperson like me who doesn’t know what to look for in terms of good / bad rings and clips, the safest option may well be to buy known brand from a known source.

Mahle pistons are probably the best in any motor. But their catalogue is a horror.

According to Mr H, Andover pistons are Italian, and top notch, so that’s what my mate will be going with this time.

His bore was fortunately untouched, so he can stay on +.020”.

His clearance was good at .0045”. His machinist reckons the piston was badly made with insufficient taper. Maybe that’s why they’re we’re NOS... (New Old Rejects) ?!

' Cortina ' pistons . Er for sleeved 920s . Thus , ther being 1100 , 1300 , & 1600 cross flow ( all ' flat top ' )
might save a buck ,
so , as youd get two sets ( four cylinders , you could get another Norton for the spare pair .

Well. . . in olde England & maybe in U S A , Capris tec . But the goe was ' 1500 ' pistons , it was said .
As there were a million aftemarket ones , in various oversizes , maybe a bit of cunning and injunuity might sort it .
Asked if theyed had any ' Blow Ups ' Getting the N Z Speedway Sidecar Chapionship ( around 1980 ) the answer was " NO " .

" Standard Cortina 1500 Pistons " think 7.000 was the redline used. Maybe . Perhaps .

Frankie17 said:

there is no issue with the circlip`s unless you choose to follow bad forum advice and change them with a clip not designed for application
or it may be a case of a vendor supplying JCC pistons with incorrect clips ?

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I hope new Hepolites for Commandos come with better looking clips than their Triumph ones.

Nigel, I was the person who proposed the "bob weight" theory of those wire circlips. Here's a picture of the circlips I removed when I got a POP and a puff of smoke cruising along at 65mph. You can see the flat spot where the circlip on the top of the picture hit the cylinder wall for a second or two.



A few people suggested that there was nothing wrong with the circlip and that doubtlessly I did not seat them properly, or I over compressed them on installation. It's pretty hard to argue against that kind of accusation because installing a circlip is like tieing your shoelace, not very memorable. You slide it in until it seats and move on. Later in that thread, Jim Comstock commented that the circlips pictured above were maybe good enough for a lawn mower engine, but not a Norton. I felt a bit vindicated on my bob weight theory.

I wouldn't use the circlips in your picture. Jim claimed that they are known to occasionally pop out. That's all the convincing I need to use something else. Of course there are people who may have used these circlips a number of times and never had one pop out at speed. Needless to say, their experience tells them that these circlips work fine...

There's some good comments from Jim in this thread:

As i posted earlier Jcc pistons are supplied by multiple vendors under many brands and in many different forms

piston Circlips supplied in the new Hepolite boxes for Norton Commando are not wire form clips seeger OEM type clips are supplied in Hepolite brand for Norton Application

please do not purchase Ford cross flow pistons for your 920 Commando (advice as above )these are not flat top pistons , 1500 Cortina is pre cross flow pistons are flat top but gudgeon pin is 24mm diameter not 17.4mm as per Commando