Issue link: https://read.dmtmag.com/i/738714
29 www.thunderpress.net THUNDER PRESS nNovember 2016n … since it has been moved to the oil pump body. The thing with the oil pump is, even though oil pressure is the same, the oil-cooled models of the M-8 get larger displacement feed rotors to ensure the fl ow of massive volumes of lubricant being pumped through the heads. Which is a subtle reminder that oil pumps these days not only lubricate, they cool. Here's how: The oil return lines deliver head cooling oil to the (bigger capacity) oil tank (under the transmission) where it passes through the separator plate (reducing agitation in the case) then gets picked up by the oil pump feed circuit, goes through the engine's critical bits, then through the oil cooler in front of the engine cases and back to the heads to repeat the cycle. Oil-cooled heads on Milwaukee-Eights have passages which are precision drilled in the heads to route oil between the exhaust valve seats for increased "pinpoint" cooling. Since it also moves faster, that oil also cools better. Whereas the twin-cooled versions pump coolant to their heads via a more familiar-looking approach. Notice that this cast-in coolant passage is also wrapped closely around each of the two exhaust valves for precision temperature control and surpassing effectiveness. This is the coolant pump for M-8s so equipped, and a damn trick device it is! First of all, it's larger than previous pumps with more capacity. But the main innovation is its ECM- controlled variable speed! Eliminates the need for a thermostat, which is nice, though far more importantly it means the pump will run harder and do more cooling when and where and as needed. The ECM reads the need, based on sensor input, then tells the pump to speed up or slow down, as required, to maintain optimal operating temperatures. Underneath the new, narrower primary cover (introduced last year on "Low" models and used on all 2017 Touring models) is a new "assist/slip" clutch. Using either nine or 10 plates (depending on model and application) this setup uses built-in ramps which increase pressure on the plates, thereby improving grip during acceleration, yet decreasing all that to let it slip when you back off sharply and/or downshift. Eases the pain for tires and drive- line… not to mention rider nerves… when negotiating treacherous roads. See "Milwaukee-Eight," page 30, column 1