I’ve been thinking that I may someday want to get the Wiseco big bore kit that would punch my ZR550 out to 615cc, but I have to admit that there are some things about it that mystify me. I’m hoping you all can shed some light on it.
I suppose my big question is about longevity. Does the bigger displacement produce more heat and wear and tear on the motor and is it a mod that shortens the life of the bike? Or is that not a problem?
I gather that the engine has to be bored out and that’s no small job, but something that should be done by a reputable shop. So does anyone know a good shop in the Portland area? Or can Wiseco provide the service? Same with the dyno testing, how do I know the shop I take it to knows what they’re doing?
I guess maybe I’m just nervous about the idea. On the one hand it sounds like the best option for really getting maximum performance out of my bike. But I don’t want to risk ruining what’s already a good thing. Help?
A breeze from the west.
‘90 ZR550 Zephyr aka “Zephanie”
‘90 ZR550 Zephyr aka “Goldie Brown”
It's not much of an increase per cylinder and all you may have to do is go up a size on the main.
If the increase in bore size is within stock oversizes and compression you wouldn't need to rejet but if you have an increase in compression then you will.
Always start a few sizes larger and work down.
I have a friend offering to sell me his unused Wiseco big bore kit and an already bored and sleeved cylinder block, and I just want to make sure it will fit my bike before I buy it. We're both pretty sure it will, but just for peace of mind, here are the details.
One bit of good news is that both the base gasket and head gasket are the same between your bike and the early 550. Also, the cam chain tensioner shoes seem to be the same as well, although the tensioner assembly itself is different. You may need to get an early tensioner. Overall, it seems likely that you can make those parts work with your bike.
Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)