Yet Another Prima Big Bore Installation Question

Beamster · Post by **Beamster** » Mon Apr 15, 2013 5:34 pm

Having read that some advise that there is a particular piston orientation required, I'm hoping for input from any who have personally done the installation.

The piston in our kit does not have an arrow on the piston as some suggest but the crown of the piston is inscribed with the diameter (58.5) on one side and "N1" or "NI" on the opposite side, both just inside the valve cutaways.

Can anyone clarify?

Beamster · Post by **Beamster** » Mon Apr 15, 2013 9:39 pm

Well, Well.
If NI upside down doesn't spell IN.
Put it on the table and walk to the other side.

BuddyRaton · Post by **BuddyRaton** » Mon Apr 15, 2013 10:17 pm

Beamster wrote:Well, Well.
If NI upside down doesn't spell IN.
Put it on the table and walk to the other side.

Don't ya hate that! Happens to all of us sometime! Keep us updated!

Post by **ericalm** » Mon Apr 15, 2013 10:37 pm

Beamster wrote:Well, Well.
If NI upside down doesn't spell IN.
Put it on the table and walk to the other side.

Ha, that is 100% a "me" kind of thing to miss. Which is how I messed up my new bike pedals.

ScooterTrash · Post by **ScooterTrash** » Tue Apr 16, 2013 4:26 am

You can also tell by the valve cutout size if I remember correctly

BuddyRaton · Post by **BuddyRaton** » Tue Apr 16, 2013 12:28 pm

ScooterTrash wrote:You can also tell by the valve cutout size if I remember correctly

Yup! Good tip...I had forgotten about that

Beamster · Post by **Beamster** » Sun Apr 21, 2013 4:15 am

ScooterTrash wrote:You can also tell by the valve cutout size if I remember correctly

Good tip. I noticed the different valve sizes but didn't notice the different flycuts.
I can imagine that installing a piston backwards could lead to piston/valve contact because of that.

It also didn't occur until now that it might be a good idea to check valve to piston clearance when installing the aftermarket head and big bore kit. Maybe just a few too many variables involved.