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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Wossner piston ring questions
Post Info TOPIC: Wossner piston ring questions
yamalama


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Wossner piston ring questions
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Hi all,

 

I am about to fit a first oversized Wossner piston but there are no instructions with the piston rings so I have a couple of questions.

Can anyone confirm that the "chrome looking" ring is the top ring , and the dull grey ring is the second ring?

Can anyone tell me what their end gaps should be?

On the Wossner website it quotes 0.004 x bore for top ring and 0.005 for the middle ring, but it doesn't say if that is only for water cooled engines.

I thought air cooled engines needed bigger gaps than water cooled.

If this is correct, and the bore is 2.87 inches, then it gives:

Top ring = 11.5 thou

Second ring 14.3 thou

For the standard Yamaha parts the workshop manual quotes 8 to 14 thou for both to and middle ring,

Your thoughts much appreciated,

 

Lama



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JOHNYBOY


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rule of thumb 4 thou per inch gap chrome ring top there will be a mark top on each ring so you dont get them upside down

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yamalama


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Thanks for your reply Johnyboy,

 

So no difference between air cooled and water cooled engines then?



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mossproof


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Regarding the colours, I think you're right it's chrome = top, but they are different thinknesses anyway, at least they are on the 350 pistons...
The maths looks ok to me. I would go with the Yam numbers. What gaps have you got?

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yamalama


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Hi Simon,

My top ring end gap started as 6 thou, but after two files made no difference to the gap, my third file overdid it massively and is now 22 thou and Steve at Totally TTRs is trying to source another set of rings for me!

How I wish I could wind the clock back.

Second ring end gap measured as 14 thou, so no adjustment necessary.

Lama



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JOHNYBOY


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why are you having to file so much on rings with perfect bore & hone should be somewhere near

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