In the quest for lighter rotating weight from a race engine, many engine builders choose to run a "total-loss" electrical system. This system removes the existing charging system from production vehicles, or eliminates it from the design altogether, and runs off the battery of the vehicle. For short sprint races, this has been an acceptable practice as batteries can generally run longer than the sprint race. The benefits are less rotating mass of the engine to rotate, as well as electromagnetic drag from the generator as it is operational. These forms of resistance can absorb a lot of energy that could otherwise be put straight to the tire(s).
With the introduction of modern electronics and fuel injection, battery voltage is critical in how an engine performs. Therefore the need to retain the charging system to keep a constant voltage to the electronics is imperative. With our conversion to fuel injection on the Gen 5.2 EFI, we have been searching for the lightest solution to this possible.
We found the charging system from the 2005 GSX-R1000 had a significantly lighter Alternator Rotor than any other motorcycle engine we had seen. In exploring this option, we found the tapered snout on both the Honda and the Suzuki were identical at 5 degrees. The rotor, however, was cupped away from the engine to meet a cover-mounted Stator. The Honda had the Rotor cupped towards the engine to meet a case-mounted Stator.
In some trail CAD mock-ups, we found that we could pull this off with some creative adaptations. Everything would be fairly straight forward with the exception of an adapter plate to be mounted on the cover to accept the Stator of the GSX-R1000, and a bracket needs to be devised to keep the Stator wires from being rubbed by the spinning Alternator.
Seen here is the adapter plate that will be machined and fastened solidly to the Generator Cover of the engine. We will machine this from aluminum, replacing the stock sound dampener that is currently mounted in the case. The base retains the "D" shape of the damper to fit snugly in the case. The center will have the stock GSX-R1000 Stator mounting hub shape machined out of it for simple installation.
The final hurdle will be to fabricate a retaining plate to hold the wires from contacting the spinning Rotor and grinding off the wire shielding. This will be done once the rest of the modification is performed. The end result will be a Generator with 2/3 less rotating mass to increase the throttle response and deliver more horsepower to the rear tire. All while retaining a constant voltage to the electrical system to support the Pectel ECU, Ignition and EFI system for reliable and steady use.
The 1st Article arrived. We needed to make a few minor alterations to the part so it would fit nicely, but they will be easy to incorporate to the run of final parts. The Boss Adapter drops into the recess of the Generator Cover that originally housed the sound damper assembly. There is a threaded boss and mounting pin in the cover that protrude outward. The Stator Boss Adaptor plate locates on those protrusions, using the threaded boss as one of the mounting points.
The Stator then mounts to the Adaptor as it would to the standard GSXR cover. However, the top bolt (10mm head at 12 o'clock) passes through the Adaptor and threads to the existing threaded boss in the Generator Cover of the NC. This is the first of three mounting points for a secure installation. The other two mounting points come from the backside, through the cover.
I located the hole positions from the inside using a center punch through the lower two Stator mounting holes. I drilled from the inside and found the holes landed between the ribs on the outside face of the cover. I chose to remove the entire ribs on this cover. In future installations, I might only remove enough rib to neatly fit the bolts without interferance.
The through holes in the cover will most likely leak unless proper care is taken to seal the hole. Here you see an aluminum crush washer under the head of the bolt. Since the cover is not flat here (it has a slight curvature to the surface) the sealing washer may not be enough. A slight counterbore to the cover at this point will help, or you can apply sealant to the area to help with the uneven surface.
This is the stock wire stay bracket for the GSXR. In an effort to reduce machine costs, we chose to modify this bracket to work for our needs. We flattened the tab at the upper right of the photo, which had a 90 degree bend originally. Once we did this, the bracket was perfect for keeping the Stator Wires from dragging on the Rotor.
Drilling a small hole for a 5mm screw, we ounted the bracket at the top of the cover in the wire plug location. This standoff was just something we had laying around, but we will have some custom machined to the exact size we require. With this length standoff, there is just enough clearance from the screw head to the rotor, and a snug fit for the wires to stay in place.
We mocked up the set-up with the cut-away cover. You can see the bracket keeps the wires away from the Rotor perfectly. This solution should be quick, easy and inexpensive for anyone to do themselves. Any of the alternatives seemed to add significant cost to the conversion.
Once the wires get to the junction of the cover and cases, they need to pass through the opening in the cases intended for this. The rubber wire plug that comes on the GSXR Stator would not fit correctly. So, we carefully cut the bottom plug from the NC Stator with slits to each wire. The GSXR wires are heavier gage wires, so they splay the plug out a bit. To prevent oil leaks at the slits, we will add sealant at assembly.
Here is the final assembly in the cut away cover. The edge of the Stator Boss Adaptor is in red. We used the red dye to identify intereference when assembling these parts. We were able to identify incorrect fit where the dye was removed. The alterations were minor, so the final parts will work great. Considering we have flipped the assembly the other direction from stock, everything fit as if it were origionally designed to use this set-up. The final alteration is to convert the connector to fit the Honda wire Harness. Our harness on the Gen5.2EFI is for a CBR1000RR, so it requires a different plug than the NCs.