GPz550 Big Bore Pistons and Cylinders - Kawasaki GPz550 Ep02

In the second installment of the Kawasaki Gpz550 refresh we are diving into the motor, removing the stock pistons and replacing them with a Wiseco big bore kit which bumps the capacity up 62cc to 615cc total.
Installing a big bore kit requires the cylinders to be machined to accept the larger pistons. In this instance the bore has increased by 3mm. Installing pistons in small displacement four cylinder bikes can be tricky in the best circumstances, but because of our large overbore the majority of the cylinder's chamfer has been removed. This chamfer aids in installing the pistons by helping compress the rings on install so we have only made this install more difficult for ourselves. Mistakes are pretty easy to make, as you'll soon see, but they're not too difficult to rectify.
Make sure to subscribe if you'd like to see this bike finished. In the next installment, we will be installing the freshly rebuilt cylinder head.
Want to see more of the Custom BMW R90/6 Project? Check out the playlist here:
• BMW R90/6 Custom build
I'm on Instagram @roodlum / roodlum
Parts made right here in Rochester, NY are available here:
shop.themotoworks.com/

[@malandro2023]

Finding this video has put a huge smile on my face. I've a GPz550 A1 that I want to throw a Wiseco kit onto, and an AHP 200x as well. Man, this is sweet!

[@HypnoticPattern]

watching the years of grime that accumulated in the engine crevasses and the pistons dropping in is a special kind of satisfying. I can't wait to hear this thing rip. It was the original 600cc class sport bike before we had such a concept. Couple guys here talk about how they would pick up one at the dealership, ride to Willow Springs or Laguna Seca, and race, win and ride home. Then everyone wised up that these were the right bikes to win on and everyone had one and you didn't have an unfair advantage anymore.

[@deanadams3099]

Hipster bike bingo finalist.

[@gordonhutchison9647]

Mines now a 670 cc from 550

[@MarkDLongo]

Is that a custom job? I haven't seen 670cc kits. Would love to learn more...I'm about to rebuild my 550 (it's a zr550 but basically the same engine as the gpz550). I was planning to go with the Wiseco 615 kit...

[@ps3shakes123]

Interesting how the bore and cc numbers parallel each other..

[@roodlum]

an interesting coincidence for sure

[@TeamVeroBeach]

Curious what did you tap the rings at?

[@roodlum]

I tried looking for my notes on this but I don't think I kept them. The kit came with a formula for calculating ring gap based on the cylinder diameter and I just went with that.