SPR is a bearing/response system where the bearing and response sit on “disks” that are inserted into the side of the yoyo. These disks can be interchanged to disks that support smaller or larger bearings.
This system was used predominately by crucial yoyos. Not many yoyos use this system today and it is quite rare. If your yoyo had a SPR system in it, you’d probably know about it.
Been having a rough time. It took me 45 minutes to have the YYE page load up earlier. My ISP has apparently fixed the issues with my connectivity. Serves me right for playing my TI-5!
Close but…Im pretty sure it was Buzz On that first offered SPR, as a kit and in their yoyos.
Crucial then offers a better version of the ‘SPR’ system and now Chico yoyos offers a ChicoAnythingKit that accomplishes the same thing but has the axle included in the setup.
My Half & Half uses an SPR system, so I bought the Crucial SPR system so I can use an A-bearing in it. The SPR kit doesn’t even fit properly. Oh, it works, but there’s a gap. Poorly done and implemented in this situation.
It seems to me that SPR kits are designed to work well in specific yoyos. I know the Buzzon SPR was designed to work with yoyos that used a metal insert bearing seat - Buzzon, Spintastic, Duncan FHZ. The SPR had a nub on the back side that fit into the space for the original bearing seat. All 3 of those brands used the same size bearing seat insert. I haven’t had the opportunity to see the newer designs.
To the OP - unless you can find an SPR kit that fits, there is no shortcut. It’s major surgery.
If you’re going from an A bearing to a C bearing, get some YYF spacers for things like the Protostar. That will at least provide you a “seat”. Just an option though, far from perfect, but has been done many times by very well skilled modders with fantastic results.