Webike Japan
CB750 Member
The second this oversized, CNC-machined A7075 billet oil pump assembly for the CB750F hit the shop bench, my wrenching instincts took over. I immediately started tearing down an old factory unit to do a side-by-side micrometer comparison. Let's be real—the unforgivable weaknesses of OEM parts, especially that original 80s cast aluminum pump, lie in the terrifying rotor deflection and high-RPM cavitation. It's a complete joke when you're pushing the redline.
But this new piece? The millimeter-level precision on the internal trochoid gears is pure engineering ecstasy. They’ve totally eradicated the sloppy factory casing clearances, utilizing extreme material rigidity to ensure zero housing flex under maximum hydraulic load. I threw the feeler gauges at it, and the rotor-to-housing gap is flawlessly uniform, making the entire lubrication system absolutely bulletproof.
However, pushing this much oil volume with relentlessly tight tolerances brings up a whole new demon: the terror of thermal drift. When that air-cooled DOHC mill starts to bake and experiences massive heat soak, the differing expansion rates between the billet pump internals and the engine crankcase can dramatically alter the flow dynamics and bypass valve thresholds.
So, I’ve got a question for you hardcore air-cooled lubrication geeks: when you're dialing in a hyper-efficient, tight-tolerance billet pump like this, how are you perfectly managing the pressure relief spring rates to compensate for extreme oil heat soak and thermal drift during sustained track abuse?
https://japan.webike.net/magazine/c.../?utm_forum&utm_medium=648&utm_campaign=46100
But this new piece? The millimeter-level precision on the internal trochoid gears is pure engineering ecstasy. They’ve totally eradicated the sloppy factory casing clearances, utilizing extreme material rigidity to ensure zero housing flex under maximum hydraulic load. I threw the feeler gauges at it, and the rotor-to-housing gap is flawlessly uniform, making the entire lubrication system absolutely bulletproof.
However, pushing this much oil volume with relentlessly tight tolerances brings up a whole new demon: the terror of thermal drift. When that air-cooled DOHC mill starts to bake and experiences massive heat soak, the differing expansion rates between the billet pump internals and the engine crankcase can dramatically alter the flow dynamics and bypass valve thresholds.
So, I’ve got a question for you hardcore air-cooled lubrication geeks: when you're dialing in a hyper-efficient, tight-tolerance billet pump like this, how are you perfectly managing the pressure relief spring rates to compensate for extreme oil heat soak and thermal drift during sustained track abuse?
https://japan.webike.net/magazine/c.../?utm_forum&utm_medium=648&utm_campaign=46100