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Author Topic: Spin-on oil filter  (Read 969 times)


  • Grand Gearhead
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Spin-on oil filter
« on: July 21, 2012, 04:09:15 am »
I have a spin-on filter on my 1977 350.  Mounted with some clear hosing connecting from and to the rocker feed.

Flow of oil, both in and out of filter, as seen while bike is running in neutral is not constant...sometimes dribs and drabs, sometimes nothing, sometimes a series of separate blobs, sometimes a constant stream of fluid.   RPMs help; the fluid moves faster, but it never settles to a constant.  Can't tell very well while riding, but seems generally reassuringly brown in the lines when I glance down.  No problems with the engine so far in 160 initial miles.

One factor may be the wider inner diameter of the vinyl tubing compared to the feed lines.  I thought it'd be self-regulating once oil had fully circulated through the system and primed (both) filter cavities.  Am I wrong?

Am I killing my engine, starving it for oil?  Do I need a high-output pump if I'm going to run this thing?  I'm getting a bit nervous and thinking about ditching the filter and slapping on a standard rocker feed line.



  • Grand Gearhead
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Re: Spin-on oil filter
« Reply #1 on: July 21, 2012, 07:34:17 am »
I would probably run a cooler before I ran a spin on filter. Do you still use the stock filter? I think you are supposed to. The filter needs to be changed at more frequent intervals because of the nature of the engine design. I have found that using synthetic oil lengthens the interval quite a bit but then again I don't use my Bullet on a daily basis as my main mode of transportation. I think the rule of thumb is to change your oil about 1000/1200 miles and the filter every time or every other time depending on how bad it looks.

If you are worried about your oil flow I would start the bike then crack open the banjo bolt on the head and see what kind of flow you are getting. It will not shoot across the room but will dribble out at a steady flow when cracked open. Check both sides. You can also crack the quill bolt while running and check the flow there. That year of bike uses a cork for the quill seal. I would make sure it is in good condition. I think those are supposed to be replaced every oil change. I read a post from one member who keeps a handfull of corks soaked in oil just for that reason.
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  • Grand Gearhead
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Re: Spin-on oil filter
« Reply #2 on: July 21, 2012, 04:24:41 pm »
Don't worry about the intermittent oil flow.

The oil that is going to the rocker arms is being pumped by the scavenge pump from the main crankcase and it only picks up oil when a sufficient amount has accumulated there.

I don't know why the British use this method but it is also used on the old BSA's and Triumphs too.
The only difference is the scavenge pump in those bikes are pumping the oil to the oil tank and some of it is diverted from the oil tank return to the rocker arms.

I'm guessing it is a carry over from the days when the upper rockers were exposed and didn't get any oil at all unless the owner squirted them with an oil can?
Even occasional scavenge oil delivered by a pump that often didn't have anything to suck was a mighty leap ahead in technology over those days.
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