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Post by 4l04ever on Jul 16, 2019 16:39:24 GMT 1
As I was refitting one of the pistons on andrewm's engine, I noticed the bottom ring was not seating correctly. On further inspection, the expander ring was in many pieces and had moved so it was double thick in places.
That reminds me why I never fit them now.
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Post by 4l04ever on Jul 16, 2019 16:41:22 GMT 1
pic  |
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Post by steve h on Jul 16, 2019 16:46:26 GMT 1
Why did Mr Yamaha san deem they should be fitted in the first place?
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Post by 4l04ever on Jul 16, 2019 16:53:49 GMT 1
They probably never ran an engine for a few thousand miles then took the rings out, as you can't see this fault until the 2nd ring is removed.
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Post by midlifecrisisrd on Jul 16, 2019 16:53:53 GMT 1
Why did Mr Yamaha san deem they should be fitted in the first place? Cue bare's response shortly 😁 Steve |
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Post by midlifecrisisrd on Jul 16, 2019 16:56:05 GMT 1
We're the pistons/rings genuine though?
I usually fit them especially with genuine but then as my bikes do approx 0 miles per year they will be good for years to come 🤣🤣🤣
Steve
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Post by 4l04ever on Jul 16, 2019 16:58:00 GMT 1
These were on Mitaka pistons, so maybe more of an issue on these than standard pistons?
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Post by dusty350 on Jul 16, 2019 17:08:27 GMT 1
Last couple of Mitaka sets I've had didn't come with expander rings ??
Dusty
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Post by jon on Jul 16, 2019 18:24:53 GMT 1
These were on Mitaka pistons, so maybe more of an issue on these than standard pistons? What country of origin were the Mitaka’s from? Jon |
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Post by raven13 on Jul 16, 2019 18:30:17 GMT 1
I ride my rd almost daily and never use the expander ring.
I was told years ago by an old mechanic that lived down the street from me not to bother with them, but for the life of me I cant remember why he said not to,lol.
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Post by earthman on Jul 16, 2019 19:42:02 GMT 1
I'll have to search for that article by Stan Stevens, can't remember if he does or doesn't fit them.
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Post by alistair64 on Jul 16, 2019 20:00:25 GMT 1
To be honest, they're so flimsy and give such little outward force that I have never understood what they do anyway.
I get the theory, but in practice??
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Post by ianboom on Jul 16, 2019 21:35:54 GMT 1
I was told never to fit them, but that was a long time ago and I can't remember why!
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Post by 4l04ever on Jul 16, 2019 22:22:07 GMT 1
These were on Mitaka pistons, so maybe more of an issue on these than standard pistons? What country of origin were the Mitaka’s from? Jon Japan... |
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Post by oldbritguy on Jul 16, 2019 22:44:49 GMT 1
Ok. So is it worth fitting them or not? I am just about to rebuild my rebored top end with new Mitaka pistons and they have been supplied with expander rings as well.
My initial thought was to fit them anyhow but did question their effectiveness as they are very flimsy.
This thread has just confused me more.
John
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Post by 4l04ever on Jul 17, 2019 1:27:41 GMT 1
I never fit them in my own engines. Have removed them from this engine too.
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Post by reedpete on Jul 17, 2019 4:17:47 GMT 1
Guys...guys...guys...
If the rings are sized to accommodate expanders then really they should be there...
However many ring sets are designed not to use them.
If you like leaving stuff out then remember second ring is optional anyway! Provides extended ring life at the expense of marginal increase in ring friction. Back in the day None of my proddy bikes ran with second ring.
I wouldn’t advocate a one ring setup on a road bike but a second ring intended to have an expander behind it probably isn’t doing very much with the expander left out...just sits there going along for the ride !
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Post by bezzer on Jul 17, 2019 7:16:36 GMT 1
Why did Mr Yamaha san deem they should be fitted in the first place? Cue bare's response shortly 😁 Steve Good point, where is he?, must be hibernation season already 😁 |
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Post by dusty350 on Jul 17, 2019 7:20:01 GMT 1
I've had a Ypvs and an Lc set of Japanese Mitaka pistons and rings in the last couple of years, and neither set had expander rings included ?? Dusty  |
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Post by Tobyjugs on Jul 17, 2019 8:36:25 GMT 1
As I was refitting one of the pistons on andrewm's engine, I noticed the bottom ring was not seating correctly. On further inspection, the expander ring was in many pieces and had moved so it was double thick in places. That reminds me why I never fit them now. Was This new parts? |
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Post by oldelsieboy on Jul 17, 2019 8:50:31 GMT 1
I've had a Ypvs and an Lc set of Japanese Mitaka pistons and rings in the last couple of years, and neither set had expander rings included ?? Dusty LC pistons do not have expander rings. OEB |
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Post by cb250g5 on Jul 17, 2019 9:07:03 GMT 1
I don't fit them.
My TDR Mitakas came with RK rings, with expanders. Didn't fit them.
I believe their purpose is to keep the noise down on cold engines, and have no effect once warmed up.
I'll take a bit of piston slap rather than the risk of them breaking up in use.
YMMV
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Post by bernardo on Jul 17, 2019 10:07:19 GMT 1
I've never fitted them. A mechanic told me years ago that they weren't really needed. Worked ok for me so far.
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Post by liffy16 on Jul 17, 2019 13:23:12 GMT 1
Just bought a piston kit for my 250lc and the rings made by TKRJ have an expander ring,think I will leave them out after reading this
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neil
Thrash Merchant
my 125
Posts: 385
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Post by neil on Jul 17, 2019 16:53:32 GMT 1
I remember taking the barrel off my 125 and noticed most of the expander ring had gone, luckily there was no damage! Are the grooves on the piston the same depth? Could you not fit two top rings? I know you would obviously have to sacrifice two sets of rings! Neil
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Post by oldelsieboy on Jul 17, 2019 17:21:23 GMT 1
Just bought a piston kit for my 250lc and the rings made by TKRJ have an expander ring,think I will leave them out after reading this I've had a Ypvs and an Lc set of Japanese Mitaka pistons and rings in the last couple of years, and neither set had expander rings included ?? Dusty LC pistons do not have expander rings. OEB |
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Post by bare on Jul 17, 2019 18:18:38 GMT 1
As expected :-) OEM Yama expander rings serve genuine purpose ; To reduce piston slap.
Expanders are/were to help keep the piston centralised in the bores.
Riken (the major after market maker) expanders are Crap quality and IMO should not be fitted as they Do break.. with ugly results.
Real issue is, as always .. depressingly low grade Aftermarket substitutes.
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Post by 4l04ever on Jul 17, 2019 20:43:10 GMT 1
OEM rings are only available as a set, and at nearly £50, I think I will have to stick with no expander ring for now.
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antos
Drag-strip hero
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Post by antos on Jul 18, 2019 15:44:23 GMT 1
Fitted them in my f2 2 yrs ago mitaka from grampion done around 4 k now and all’s fine, 👍
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Post by mattybeckett on Jul 18, 2019 18:06:27 GMT 1
I've always binned them.
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