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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Piston ring advice needed
Post Info TOPIC: Piston ring advice needed
dlee22


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Piston ring advice needed
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Hi there,

I've got a ttr thats burning oil and got the piston off and would like bit of confirmation of the size. I assume as there is no plus 1mm marker im safe to assume that its standard size.

 

Any advice would be appreciated and if anyone could recommend parts that might be worth replacing whilst in there that would be really helpful.

 

Thanks for your time etc.

 

Dan



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Daniel Lee
TTRfan


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It's almost certainly a Wiseco piston but I can't see it in their current catalogue. Standard is 72.95mm and the oversizes usually go up in 0.50mm steps. What is the bore diameter of your barrel? That will give you the answer. My guess is that as it's not a standard Yamaha piston you probably are into an oversize.

Usually a good time to thoroughly check everything in there but, whilst apart, it's worth fitting new valve stem oil seals after cleaning up the head and valves and lapping the valves in. Also check the timing chain and replace if suspect.

Brian



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dlee22


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Hi Brian,

Thanks for the help, ill measure it tonight!

Dan

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dlee22


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Hi Brian,

The barrel on it measures 75.54 mm which makes wonder if it could be for the 325cc kit wiseco?
I dont suppose you know the bore size of one?
The bike was from a previous member on here who used to enduro it so a larger piston would have suited his needs.

Thanks

Dan





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Daniel Lee
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The 325 kit has a bore of nearly 82mm so it's not a 325 kit.

The Wossner pistons are:

PistonOversizesPiston Kit
Size(mm)Part No.
(mm)  
72.95Standard8646DA
73.45+0.58646D050
73.95+1.08646D100
74.45+1.58646D150
74.95+2.08646D200

So it's at least 2.5mm oversize. Maybe Wiseco did a bigger oversize piston than Wossner?

Anyone else throw any light on this apparent oddity?

Maybe contact Wiseco with the reference number and ask what it is or make contact with the previous owner?

Brian

 



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dlee22


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Hi Brian,

Ive taken a look at it myself now and the internal dia was actual 75.94 so it must be a +3.0mm piston. I do have a std barrel and piston i could use but im not convinced which one to put on. I'm going to try to find an email address shortly.

Thanks again

Dan

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Daniel Lee
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Would that give 270cc?

 



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dlee22


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Not sure, I've just ordered standard rings for the standard barrel and piston for now and may put the larger ones on at somepoint once i need a bit more power and can find new rings.

Thanks for your help!

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Daniel Lee
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Email, or preferably ring, Wiseco - they should be able to give you a reference for new rings and a part number.



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dlee22


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Hi Brian,

I think ive found out what the number corresponds too.... a 76mm Kawasaki zx9r 1998-1999 oversized piston!

I may have measured it wrong when i got 75.94mm then or i guess would the rings would compress slightly 

 

Dan



-- Edited by dlee22 on Tuesday 20th of December 2016 09:21:10 AM

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Daniel Lee
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I found that but dismissed it as being wrong! What are the chances that the gudgeon pin, crown height etc would match confuse

At least you can buy a set of rings for it now biggrin

I thought that boring out to +2.00mm left the sleeve wall a bit thin. What is the width of yours please?

Brian 



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