|
|
Post by spudscossiecobra on Feb 20, 2021 17:01:28 GMT 1
Hi all just had my barrels rebored and they supplied the pistons it’s just that my barrels are 1ua and the pistons supplied say 31k is there a difference?
|
|
|
|
Post by bare on Feb 20, 2021 18:29:22 GMT 1
Don't believe so. AND .. IF there were it would only be in Genuine Yamaha pistons.
Aftermarket ones aren't mfg'd to anywhere near the same detail level.
|
|
|
|
Post by dusty350 on Feb 20, 2021 18:56:26 GMT 1
Yamaha pistons have a different part number prefix - 31k 11631 00 94, and 1ua 11631 00 94 for the standard sized piston. So some difference, but I dont know what the difference is and whether it's enough to stop you using a 31k in a 1ua ?? Dusty  |
|
|
|
Post by midlifecrisisrd on Feb 20, 2021 19:23:14 GMT 1
I've used 1ua pistons in a 31k and 31k's in 1ua's with no problem
When it comes to aftermarket pistons you only get 31k
Dimensions are the same
Pistons and rings for 1ua genuine are different which suggests a ring/groove difference only
Steve
|
|
|
|
Post by reedpete on Feb 20, 2021 20:26:16 GMT 1
Thought the crown was slightly different to complement the different head profile, but that might be my meds playing up !
|
|
|
|
Post by spudscossiecobra on Feb 20, 2021 21:13:47 GMT 1
So no difference in skirt lengths so should be ok
|
|
|
|
Post by jon on Feb 21, 2021 10:01:20 GMT 1
It would be the compression height I’d be worried about rather than the skirts (as they can be trimmed if too long). But as others have said there must be a minimal difference as 31k pistons can be used in 1UA cylinders (personal experience) so I guess the reverse is true (an backed up above by people).
If you think until recently most LC owners were using 31k pistons which do have visible differences such as ports and lack of expander rings.
Jon
|
|
|
|
Post by midlifecrisisrd on Feb 21, 2021 12:24:25 GMT 1
Thought the crown was slightly different to complement the different head profile, but that might be my meds playing up ! You probably have a point there but as the UK 1ua's had 31k heads fitted it cannot be critical as Yamaha fitted them this way Steve |
|
|
|
Post by reedpete on Feb 21, 2021 12:38:50 GMT 1
Not even sure that it’s only banshee pistons that have shallow crown.....just remember something about it....
I’m sure someone knows full sp, anyway agree not a issue as long as chamber volume and squish are correct.
|
|
