Got home, checked the oil, one quart low. Been 1200 miles since my last service. I normally run about 1/2 quart low. Put the bike on the lift, checked primary fluid level. Good. Pull the sump plug..........22 ounces of oil drained out in 15 minutes, and was still "stringing" when I put the plug back in. Sumping? Yes? No? Some other challenge(s)? Options? Courses of action?
Thanks!
Here's another of the new OD6 and oil spout. I think the new oil spout will ease my mind about the dipstick blowing out and getting oil all over the place like it has so many times before. Putting a temp gauge in place of the air temp gauge on the inner fairing.
I have a theory that I believe is worth exploring; although it does involve reading another short novel.
It is my sense that conditions resulting in an increased pressure differential across the scavenge pump’s inlet and outlet ports (lower relative inlet pressure) will also result in a reduction in the pump’s efficiency.
Under certain conditions, early Twin Cam’s provide us with a dramatic example of reduced scavenge pump efficiency. Twin Cam’s manufactured prior to ’02 were prone to purging large amounts of oil (16 to 32 ounces) through the breather in a single event. Oil pump alignment was identified as the reason for the purge, but the pump alignment always remains constant; the purge is intermittent and requires a trigger event. IMHO the trigger event is anything that causes oil to move forward to the upper front area of the oil reservoir and obstruct the vent hole. Vent hole obstruction begins with a reservoir that is well topped up or overfilled. Moving the oil forward involves deceleration, aggressive braking or something like one of those incredible downhill grades on eastbound I-70, west of Denver.
With the reservoir vent obstructed, the scavenge pump quickly pressurizes the reservoir, creating a backpressure in the scavenge pump. The pressure in the reservoir also forces oil through the vent into the camchest, contributing to the quantity of oil purged. Considering that more than 50% of the scavenge pump’s output is air, I believe that increasing the relative pressure across the pump’s outlet port results in a cavitation inside the pump. Cavitation reduces the pump’s efficiency to a point where it pumps at a fraction of its capacity; meanwhile the feed pump continues to fill the engine with oil. I haven’t confirmed this theory, but since the oil reservoir vent was relocated to the oil filler cap area, issues with purging nearly a quart of oil in a single event have simply disappeared in ‘02 and later TC’s.
According to this theory, any circumstance that results in an increased pressure differential across the scavenge pump, reduces the efficiency of the scavenge pump (to a relative degree). The S&S reed valve is designed to lower crankcase pressure while increasing pressure in the camchest and oil reservoir. If this theory is credible, then the installation of the reed valve will have a negative impact on the scavenge pump’s efficiency, increasing the oil level in the crankcase.
If you have a wetsumper, validating this theory would be relatively simple. Use a consistent and reliable method to establish a baseline for the amount of oil running in the crankcase (future post). Modify an old filler cap to accommodate a large diameter (5/8” +) vent hose. Run the test again with the oil reservoir vented through the modified filler cap. If there is no substantial difference in the amount of oil running in the crankcase, the theory is busted. If the theory is validated it will help bring some valuable focus to the search for a solution.
djkak
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Topic: Sluggish (Read 38738 times)