Differences
This shows you the differences between two versions of the page.
| Next revision | Previous revision | ||
| techtalk:ih:engmech07l [2020/09/19 00:23] – created hippysmack | techtalk:ih:engmech07l [2023/12/27 02:01] (current) – [Dr Dick on the slinger and oil loss] hippysmack | ||
|---|---|---|---|
| Line 2: | Line 2: | ||
| ====== IH: Engine Mechanicals - Sub-07L ====== | ====== IH: Engine Mechanicals - Sub-07L ====== | ||
| ====== Dr Dick on the slinger and oil loss ====== | ====== Dr Dick on the slinger and oil loss ====== | ||
| + | Article by Dr Dick of the XLFORUM ((https:// | ||
| + | |||
| + | 1952-1962 used the old 'daisy wheel' gear that physically sealed to a spring loaded top hat in the cover. \\ | ||
| + | These had great oil control but are pretty restrictive to air flow. Bad air flow can rob hi RPM horsepower. \\ | ||
| + | Race bikes used big breather passages, fittings, hoses and pass lots more oil. \\ | ||
| + | |||
| + | Bikes 1952-1976 work different than 1977>. \\ | ||
| + | 1977> don't have as much oil flying around in cam chest and the 1977-1978 one way foo foo keeps air flow volume to atmosphere low. \\ | ||
| + | These bikes tend to drip from the tube after a ride. Oil gets trapped in the nook and crannys of the foo foo, then leaks out. \\ | ||
| + | |||
| + | 1976< is a totally different dynamic. \\ | ||
| + | The crankcase volume under pistons is much smaller than 1977> and air flow to the cam chest is much more restricted. \\ | ||
| + | The 1977> cam chest can act as a air reservoir for crankcase volume and the foo keeps the amount air in the cases low. \\ | ||
| + | Less air equals less pumping losses. Used oil gets picked up in the crankcase itself (not in the camchest). \\ So the slinger has an easier task in 1977>. | ||
| + | |||
| + | Not so for 1976<. \\ | ||
| + | Oil collecting in the crankcase needs to be blown into the camchest to be picked up by the return pump. \\ | ||
| + | High air flow from the crankcase thru the timed breather to the camchest evacuates the crankcase oil good. \\ | ||
| + | That same high flow ' | ||
| + | As you allow free air flow thru the motor, you also allow free oil flow too. So far, so good, right? \\ | ||
| + | |||
| + | The down side: As air flows in and out of the camchest vent (puke tube), so does the well suspended oil. \\ | ||
| + | Race bikes can pass a lot of oil to atmosphere way more than acceptable for a street ride. \\ | ||
| + | So to separate oil from air, a slinger is used. It functions by forcing air thru a small passage that has a spinning disc. \\ | ||
| + | The disc sets up centripetal force in air passing thru passage. \\ | ||
| + | The smaller the passage, the better the oil control and the smaller amount of air that can freely pass. Bad for power-good for oil control. \\ | ||
| + | Reducing the slinger clearance (to a degree) is like putting mufflers on a race bike. \\ | ||
| + | The MoCo is more interested in happy customers than the efficiency of a single sub-system. \\ | ||
| + | |||
| + | Everyone seems concerned about oil loss. Not a word about the other side of the coin - the cost in performance of good oil control. \\ | ||
| + | The factory knew their customers wants and it will cater to that market. Good business sense. \\ | ||
| + | In the boardroom, the question was: \\ | ||
| + | How do we free up more power while keeping oil loss at a level that the customers are accustomed to? \\ | ||
| + | From past experience, they knew that oil evacuation was more important than air evacuation. \\ | ||
| + | And they learned that keeping air speed in the camchest low allowed oil in the cam chest to 'rain down' to the return pump. \\ | ||
| + | (instead of staying in suspension and relying on a restrictive slinger to keep flow thru puke tube and to the underside of bike acceptable. \\ | ||
| + | |||
| + | So if they could concentrate the crankcase oil in a trap, then blow that oil into the camchest with a small amount of air; \\ | ||
| + | They get the most power with the least chance of oil loss. \\ | ||
| + | A look at the shape of the transfer passage between the crankcase and the breather valve shows the result of that line of thinking. \\ | ||
| + | So in mid 1962, they reduced oil pump capacity but increased the return to feed ratio. Less oil in means less oil to move and less drag. \\ | ||
| + | More return over pump helped more yet. \\ | ||
| + | The small pump dried the camchest well enough that the slinger could be opened up = more air flow. \\ | ||
| + | Good-bye power robbing daisy wheel - hello fender washer. \\ | ||
| + | |||
| + | The 1962-1971 oil pump has a smaller feed side than the 1961<. Compared to the 1961<, the return is bigger in the -62 pump. Less feed, more return. ((https:// | ||
| + | The 1972 pump feeds and returns more than any of the previous. | ||
| + | |||
| + | |||
| \\ | \\ | ||
