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998cc Piston Rings Yoshi / Z1000j

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johny brando
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998cc Piston Rings Yoshi / Z1000j

#1 PostAuthor: johny brando » Sun Oct 07, 2018 6:35 am

Bit of a curly one here ... I'm assembling what to me was and is an unknown basket case motor this is going to be just a spare 900 engine it was running a Yoshi 998cc kit = 69.4mm pistons which all appear to be in good shape . I'm considering re-ringing it....although there appears to be no real need to ( as theres no visible blow by & all measures up good ) .Thought i'd ask if any one has tried Z1000J rings on Yoshi Pistons in a 998 (69.40mm ) bore as they are apparently the same bore of 69.4mm too...... I'm thinking maybe I'd get NPR set kits for Z1000j as I have NPR rings in my 900 at the moment & they are quite good & reasonably priced too. Thing is..... I don't know about the Ring sectional sizes on Z1000j rings ????? I can't find any data on that ! The Yoshi rings themselves are Top = Chrome & 1.48mm thick ( likely was 1.5 ) . Middle = black- Cast ? 1.50mm thick . Oil control= 3 Piece overall combined thickness 2.50mm with Close step corrugation 3mm C/C expander. Doe's anyone know how those dimensions might compare with Z1000j rings ?? Cheers, Johny B.

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z1bman
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Re: 998cc Piston Rings Yoshi / Z1000j

#2 PostAuthor: z1bman » Sun Oct 07, 2018 10:37 am

i am certain z1000j rings are 1.2mm standard

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Al
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Re: 998cc Piston Rings Yoshi / Z1000j

#3 PostAuthor: Al » Sun Oct 07, 2018 11:05 am

Just measured some standard J piston rings on an existing (worn) piston.
69.4 mm (these particular ones at 1.00mm oversize)
Top ring (very worn) 1.00mm dead but quite loose fitting
Middle ring 1.2mm
Bottom oil control assembly 2.35mm measured outside to outside of hard rings.
You'll be aware of the oil control problems of the J models and the finger was pointed at, variously; bore treatment, pistons and/or rings at different times.
If youve got a set of pistons showing no signs of blow-by and a good set of rings with no scores, gauges or slots i would stick with what you have.
When mine was still 998 i tried several new sets of rings on what had been fitted which was late type oversize J3 pistons and nothing seemed to stop it smoking.

AL
1981 J1

johny brando
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Location: australia

Re: 998cc Piston Rings Yoshi / Z1000j

#4 PostAuthor: johny brando » Mon Oct 08, 2018 3:48 am

z1bman wrote:i am certain z1000j rings are 1.2mm standard


Thanks very much for that sound info. All the best.

johny brando
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Posts: 246
Joined: 3rd Aug 2013
Location: australia

Re: 998cc Piston Rings Yoshi / Z1000j

#5 PostAuthor: johny brando » Mon Oct 08, 2018 3:54 am

Al wrote:Just measured some standard J piston rings on an existing (worn) piston.
69.4 mm (these particular ones at 1.00mm oversize)
Top ring (very worn) 1.00mm dead but quite loose fitting
Middle ring 1.2mm
Bottom oil control assembly 2.35mm measured outside to outside of hard rings.
You'll be aware of the oil control problems of the J models and the finger was pointed at, variously; bore treatment, pistons and/or rings at different times.
If youve got a set of pistons showing no signs of blow-by and a good set of rings with no scores, gauges or slots i would stick with what you have.
When mine was still 998 i tried several new sets of rings on what had been fitted which was late type oversize J3 pistons and nothing seemed to stop it smoking.

AL

Thanks for that good info ...& yeh , I remember the J1's blowing like Billy-O ...but i thought they changed the rings on the J2's & sorted that oil issue out ! appears NOT !!!! We'll thanks to your input it seems that they would not fit any way & thats just as well now -aye !!! haha . Thanks again for your help. Cheers Lee.


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