Piston 1st oversize 80-82

[JCW]

Looking for an 80-82 xs11/xj11 1st oversize +0.25mm oem piston and ring set.

Thanks

Tried ebay and some of the vintage parts places without luck.

[D0wn5h1ft]

Just the piston:

http://www.ebay.com/itm/YAMAHA-NOS-P...f1c0be&vxp=mtr


Piston with Ring:
http://www.ebay.com/itm/YAMAHA-NOS-P...f184d3&vxp=mtr

[JCW]

thanks for looking but I really wanted the higher domed pistons from 80-82.

but beggars cant be choosers...

[D0wn5h1ft]

thanks for looking but I really wanted the higher domed pistons from 80-82.

but beggars cant be choosers...

You should specify which bike you're buying for in the future. It helps people track stuff down for you. Also, I'd make sure you're replacing it with pistons that match the ones you already have in. A mismatch and I can't even imagine what would happen, best case scenario stumbling that can't be fixed. Worst case scenario, bent crank.

[JCW]

You should specify which bike you're buying for in the future. It helps people track stuff down for you. Also, I'd make sure you're replacing it with pistons that match the ones you already have in. A mismatch and I can't even imagine what would happen, best case scenario stumbling that can't be fixed. Worst case scenario, bent crank.

I thought I was being pretty specific in my first post.
And I have two just need one more.
You're reading way more into this than you need to...

[D0wn5h1ft]

I thought I was being pretty specific in my first post.
And I have two just need one more.
You're reading way more into this than you need to...

Missed that 80-82 part. That's my bad. What are you trying to do with your engine? Full bore and hone or replacing pistons and rings to try and gain compression?

[JCW]

short story- the second one. more compression on an early head.

long story- i feel the early head is choked at the current displacement above 8000rpm. going with larger pistons will just make this worse.

plan on opening intake throat to 90% valve diameter (shooting for 31mm+ at the throat), cams with increased lift and good valve job.

i calculate a mach index of 0.57 bone stock at 8000 rpm.

The mach index for maximum volumetric efficiency is .5
When Mach Index = .55 to .60 the combination is CHOKED at that RPM.

with the mid level megacycle cam i gain lift to .380 and drop the mach index to 0.52
may even spec out a slightly higher lift of .390 for a mach index closer to 0.5.

Plan on just using another stock intake cam on the exhaust side to save some $$$.

[JCW]

found one

Thanks for looking