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46 Chief quick new guy sumping question

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  • 46 Chief quick new guy sumping question

    I have read some posts on the Chiefs sumping oil down into the case after they sit for a long time. So, my question is, "IF" the engine sits and now has too much oil in it, will it even out after it runs for a bit and return to a normal level? OR will it always have too much oil in the case and never go to normal oil level.
    Jim

    AMCA #6520

  • #2
    Jim, I only had mine wet sump one time so I'm by no means an expert, but it's my understanding that the pump will pull oil out of the sump ....at a very slow rate...until the level is at the pickup tube where it's supposed to be. I can guess it depends how much oil has drained into the sump because pulling those flywheels through a few inches of oil might not get you started, then there's the smoke!
    Pisten Bully is Harry Roberts in Vermont.

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    • #3
      Howdy sir,

      ironically, that oil pump on your machine is really only a pump on the scavenge side, the feed being merely a metering device through an ineffective felt seal to the timing side main shaft. Unlike the 48 and later gear pumps, 46’s with the more elaborate iron pump can wet sump over time but note nearly as quickly or thoroughly as the aluminum pumps. Your motor uses piston movement and very small crankcase volume relative to piston displacement at BDC to lube your valve train. Filling up this small crankcase volume with oil borders on hydraulicing it, stresses your rings and results in incomplete combustion of oil forced past them and carbon buildup as the oil has nowhere to go before the scavenge evacuates the sump back down to the level of the pump intake. If you are not inclined to drain off your oil tank into a dedicated storage container before a long sit then when starting a machine you know to be thoroughly wet sumped, get it started, verify return with the oil cap off and maintain revs at as low a rpm possibly till your oil tank refills to normal level. It will no doubt be a smoker during this exercise.

      i might add, there is a pickup tube for your scavenge pump that determines/maintains the “desired” level in the sump, your scavenge side will handle much more volume, so to speak, as it must deal with aerated oil volume, so yes, your pump will easily return sump levels to desired level. Back in the day, performance oriented owner/racers wanted minimal oil flailing around creating drag and retaining combustion heat. They adjusted their scraper (on pre mid 47’s) as close to the flywheels as possible and the lowered the scavenge pickup tube (pre 47 sump valve) to the floor of the case as possible. The latter believed to get the oil back in the tank quicker where it could be cooled.
      Last edited by PRG; 02-16-2021, 06:16 PM.
      Cheerio,
      Peter
      #6510
      1950 Vincent - A Red Rapide Experience

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      • #4
        Thanks guys! I was just wondering how that worked. I took it out for a spin "around the block" (about 5-6 miles) today as it was up to 46F. Jan. 7th was the last time I had it out, so it's only sat for 1 month. It started easily and ran fine with no smoke. I've only owned this since late Oct. and haven't had a lot of time on it, but I've been removing the oil cap after I start it to make sure the oil is pumping out of the return nicely. It sure is a fun bike to ride after I've been riding VLs. My Indian has the left throttle and right shift. I have no intention of reversing it. I LIKE that it's different than my VLs.
        Jim

        AMCA #6520

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