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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Piston Ring Order
Post Info TOPIC: Piston Ring Order
TTR2501966


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Piston Ring Order
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Hi all,

I'm looking for clarification please. I've read in a few posts in here that the top piston ring is the ring with the marking. As I see it the only ring that will have a certain orientation, and thus require marking, is the scraper ring - because it's important what way the taper faces.However the TTR spec on page 31/2-7 states the scraper ring is the 2nd ring. Also the picture on page 162/4-56 shows the 2nd ring to be the ring with marking. You would expect the compression ring(without marking)to be on top as it will stop the hot gas reaching the scraper ring.

Perhaps the confusion is the picture on page 162/4-56 looks, at first glace, as though it is pointing to the top ring. Or perhaps I'm the one that is confused. Can anybody confirm?

I'm surprised that the Japanese would have 2 rings and their grooves the same thickness in the first place as it allows for confusion and mix up. The Japanese normally avoid this at all costs - they call it 'Poke Yoke'.

Thanks

Tony



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mossproof


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I agree with your findings re the scraper ring being the second one down and the only one with an asymmetrical profile requiring a marker to show which way up (mark uppermost)


The picture shows the joint of the second ring down circled and enlarged to show the presence of the marker, confirming that as the asymmetric ring.

The Wossner pistons we are using for the 350 big bore also have symmetrical (on the outer edge) top ring, asymmetric second ring, although they are helpfully coloured differently and both marked on one side.


Unless anyone pipes up soon with info to the contrary, I'd go with that although it does seem a bit counterintuitive!



-- Edited by mossproof on Tuesday 16th of July 2019 09:24:05 PM

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TTRfan


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It's a long time since I have rebuilt an engine Tony and, when I did, it wouldn't have been with a genuine Yamaha piston.

Also, I am pretty sure that I haven't got a new Yamaha piston and rings to go look at hence me not replying to your question.

I do however recall the instructions in the manual not making sense or the rings not being as described but my memory isn't good enough to recall what action I took - sorry disbelief

In the circumstances go with what you think best and I would trust Simon's opinion as he has rebuilt more engines than me wink

Brian



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TTR2501966


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Thank you both for your replies. Much appreciated. I done some more internet searches and it appears the tapered/angled ring is the second ring pretty much all of the time.



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TTRfan


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Hi Tony. Good to hear you got it sussed biggrin

I am worried that I may have given wrong advice at some time in the past. If you can recall which threads are involved, could you PM me the links please?

Cheers

Brian



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TTR2501966


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Hi Brian,

Sorry for the delay. Can't remember the threads. Think I just searched 'piston rings'. If I get a chance I'll take a look.

Cheers

Tony



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TTRfan


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Thank you Tony. I need to get it right!

Brian



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