987cc Bore: Piston Rings??

[DogsbolloxofZ1B]

I'm doing some work on a Z1A thats got 69mm bore = 987cc. Anyone know who would have made this size piston as I would like to re-hone & fit new rings.

Ta.
Mike

[Iain marshall]

Mike if there yoshi pistons 68.7,hope you have better luck than me finding them.In the end i picked up a good set of standard barrels and piston.Was talking to Chris about the ring problem and he seemed to know of a company who could make one off ring sets,think they were going to work out too expensive

[DogsbolloxofZ1B]

Thanks for that info. The bore is 69.002 so I suspect your correct about the piston dia. I'll have a chat with Chris and maybe SERDI UK over in Cowley.

Mike

[prowlerz1]

are they any markings on the piston crowns or where the gudgeon pin sits ????

[DogsbolloxofZ1B]

ProwlerZ1,

I'll remove the barrels tomorrow and let you know. I'll have to clean the crowns too as they're covered in a very thick carbon deposit, the worst I've seen.

[Thezedsintheshed]

Not sure if this will be of any help but here goes,

I did some work on an engine years ago ( around 20 plus years back ) , that engine had the same size bore kit fitted and I seem to remember that it was either an MTC bore kit or a Henry Abe bore kit,
anyway's from memory I am 99% sure that the ring sets matched one of the standard sets supplied by Wiseco.

I have dug out this Wiseco link which might help you to match up the piston rings that you are looking for
http://www.wiseco.co.uk/_private/07/Comp-Rings.pdf

As a last resort if the rings on your pistons don't match up and the Wiseco rings are thicker then it might be an option to re machine the ring grooves in the pistons ?

cheers
Phil

[Thezedsintheshed]

Just had a look through the Wiseco site,

69mm bore is the same size as an 810cc big bore kit for a GPZ750 from 1980 - 1985 , so the ring sets should still be easy enough to get hold of

[DogsbolloxofZ1B]

Thanks for taking the time to look into this and it looks promising. Haven't had time tonight but will remove hte barrels tomorrow and check for markings etc.

Mike

[DogsbolloxofZ1B]

I'm no David Bailey,, but here are some images of these pistons.

[Iain marshall]

Will be interesting to see how the 810 ring sizes measure up with your yoshi pistons.Just a thought are the rings fitted the right way up?came across that a few times in the past.Was causing oil burning problems.

[Pigford]

Pop Yoshi pistons.. very neat

[DogsbolloxofZ1B]

I need to check the ring orientation, BUT, these pistons all have a number of marks on their OD up & down the skirt that look as though the pistons
have been in contact with the liners, little contacts 1/8" sq. I'm wandering whether boring STD 900 liners out to 69mm (1.5mm on rad) isn't at the thermal limit of the liners, therefore expansion & contraction has caused these imperfections. They don't show up on camera to well but when you measure diameter at good & bad points it varies by 0.005".

The owner wants his bike returned to stock so need to have some new liners made. Anyone had any made recently?