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Post by panzermatt on Nov 2, 2018 18:14:20 GMT 1
Having just recieved a pair of piston rings in't post from herr Panzer owner norbo, i have a question.
does anyone use the expansion ring? i thought i saw stan stephens (praise be upon him) saying ditch them. what is their purpose anyway?
thanks in advance.
matt
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Post by stusco on Nov 2, 2018 18:17:09 GMT 1
Can o worms
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Post by midlifecrisisrd on Nov 2, 2018 18:29:07 GMT 1
I'll start
I usually always fit them, especially genuine
Had to take them out on a ypvs build as they were too tight in the bore with them in. Was new rings in used pistons/bores so suspect the pistons were of a wierd make
Steve
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Post by jon on Nov 2, 2018 18:30:46 GMT 1
This is one of those topics that divides opinion.
A bit like the YPVS piston tang in an LC, wider tyres on standard rims, oil, etc.
This is just my opinion, and I’m almost sure others will disagree. BUT-and this is the important part, how many have measured the depth of the piston ring groove then the ring and expander?
Yamaha San, obviously thought they were a good idea as they feature on the standard rings.
Measure the piston ring depth on the piston. Then the ring itself and the expander ring. If it all adds looks like the tolerances are OK then fit them. Do a ring gap measurement too. The last engine I build had good top rings, but the lowers on both pistons needed the ring gap filing. The expander is on the lower ring so ring gap and groove thickness are vital.
Leave them out and you won’t have a problem, just a sloppy fit.
Jon
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Post by mikee on Nov 2, 2018 19:53:29 GMT 1
Leave them out
Were originally to deal with a wide range of oils , but modern stuff negates the requirement
Mike
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Post by earthman on Nov 2, 2018 21:29:57 GMT 1
"i thought i saw stan stephens (praise be upon him) saying ditch them" Correct, I saw that in the article too. |
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Post by mellow on Nov 2, 2018 23:18:45 GMT 1
I thought i read recently that the genuine lower rings were not as deep hence the ring expander. But if not genuine rings and the lower ring is as deep as top one no need for expander  |
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Post by jon on Nov 3, 2018 8:41:11 GMT 1
I thought i read recently that the genuine lower rings were not as deep hence the ring expander. But if not genuine rings and the lower ring is as deep as top one no need for expander Yes Mick I heard this too. Therefore if a ring has been made narrow enough for an expander and comes with it, I’d fit it and check; otherwise it will be loose in the groove allowing piston slap. Jon |
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Post by cb250g5 on Nov 3, 2018 8:56:01 GMT 1
Well I don't fit them.
Stripped a few engines over the years, to find the odd one broken & a few bits missing.
I believe their purpose is to keep piston slap a bit quieter, until the motor warms up, so no real downside in leaving them out.
You'll not get a consensus on here though...
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Post by oldelsieboy on Nov 3, 2018 9:39:16 GMT 1
LC pistons do not have the expander ring fitted.
OEB
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Post by midlifecrisisrd on Nov 3, 2018 11:57:17 GMT 1
LC pistons do not have the expander ring fitted. OEB AFAIK either do banshee Steve |
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antos
Drag-strip hero
Posts: 298 
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Post by antos on Nov 11, 2018 20:23:08 GMT 1
Fitted them in my rebored f2 , year and a half ago , Makita pistons and rings no problems👍
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Post by Denzil on Nov 15, 2018 8:25:03 GMT 1
I always buy Mitaka pistons and rings, they come with the expander ring and I always fit it, the bottom groove is slightly deeper so I fit them as they are supplied. Never had a problem. I get PJME to do the reboring and supply the pistons.
My thinking behind this is, it costs a lot to produce the pistons etc and if the feedback from customers etc says they are not used, then Mitaka would not bother to produce them along with the pistons rings.
This is just my opionion. Some of the hardend engine builders will be along soon to advise on what they do.
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Post by earthman on Nov 15, 2018 8:38:16 GMT 1
This subject looks to be another 'can of worms'just like the gearbox oil.
I'm surprised that there isn't a concrete answer especially when it comes to such an internal engine component.
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Post by jon on Nov 15, 2018 19:21:12 GMT 1
I always buy Mitaka pistons and rings, they come with the expander ring and I always fit it, the bottom groove is slightly deeper so I fit them as they are supplied. Never had a problem. I get PJME to do the reboring and supply the pistons. My thinking behind this is, it costs a lot to produce the pistons etc and if the feedback from customers etc says they are not used, then Mitaka would not bother to produce them along with the pistons rings. This is just my opionion. Some of the hardend engine builders will be along soon to advise on what they do. +1 If the groove has been made deeper during manufacture to accommodate the expander I would fit it. Even if it did split I can’t see how it could escape the ring? I’ve never seen a split one and have seen close to a double figure number of engines with them in. Who knows we’re the paranoia came from? And more importantly was that on a engine that hadn’t been abused in some way or put together incorrectly? Jon |
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