DR350 Oil Check Valve....

Discussion in 'Thumpers' started by Sigean, Nov 18, 2020.

  1. Sigean

    Sigean Adventurer

    Joined:
    Apr 23, 2016
    Oddometer:
    40
    Location:
    Devon UK
    Hi,

    New to this Forum, but have shared a few threads on other bikes over the years. I have just finished renovating a 1994 DR 350 and am about to put it on the road (in Devon, in the UK). But I have a problem with the oil circulation - having filled the engine with about 2l of oil I cannot see it being circulated round the engine, viewing through the oil filler. The engine runs well, and the couple of hundred metre rides up and down the local road has revealed no problems, but I have seen a few threads on the oil check valve and its role in the engine's oil system, and somehow this has worried me. I recall taking this valve out and returning it to the engine during the rebuild, but are there any installation issues others might be aware of? What is the ball diameter (a PO might have fitted a wrong size)? Should the assembly be changed as a matter of course? It looked fine to me when I examined it, but hadn't seen one before.... Any comments welcome, before I take the bike for my first ride!

    Kind regards,

    Sigean
    #1
  2. XDragRacer

    XDragRacer Long timer Supporter

    Joined:
    Mar 25, 2009
    Oddometer:
    5,272
    DISCLAIMER: I'm totally unfamiliar with the DR350.

    On other motorcycles, the oil filter bypass valve comes into play ONLY when the oil filter becomes clogged. Unless, perhaps, your oil filter bypass valve has been installed backwards, no obvious problem surfaces, given I'm ignorant of DR350s.

    A knowledgeable inmate doubtless will respond with some useful information for you; maybe found on the DR350 thread; last page here:

    https://advrider.com/f/threads/dr350-thread.230695/page-3164
    #2
  3. Sigean

    Sigean Adventurer

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    Apr 23, 2016
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    40
    Location:
    Devon UK
    many thanks for this, but I am talking obout the "Check Valve", not the bypass valve for the filter. two different things - the check valve is a non-return valve sited at the bottom of the LH crancase half, covered by the clutch cover. But many thanks for the thought and I will look at the link you suggest.

    Kind regards,

    Sigean
    #3
  4. NJ-Brett

    NJ-Brett Brett

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    Location:
    Southern New Jersey
    If all the oil does not run into the motor after a ride, the check valve is working.
    You should make sure oil is flowing in and out to the tank, by looking or other method.
    With a cold motor on a cold start, oil level should drop a bit as oil gets pumped into the motor and takes a bit to drain and get pumped out.
    On most bikes you can see the return oil flowing into the tank...
    #4
  5. Beezer

    Beezer Long timer Supporter

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    so... you do not see oil returning when the engine runs? that could be because of where the return pipe is...

    [​IMG]

    as mentioned, the check valve is to keep oil from draining into the engine when not running. if the bike sits long enough, it will drain back anyway. that is called "wet sumping" and is a problem on all "dry sump" engines. normal procedure is to fill the oil & run the engine. when you shut down, check the oil level and adjust if required. if you check a few days later, it will be lower... do not add more oil! its all still there, just down in the engine sump area. start the engine and it will come back to normal. thats why we always check oil just after a run.

    and as stated, if the oil is full, and "scavenged" (not drained back to the sump" you will see a drop in quantity when the engine starts. an oil level check is only valid right after shutdown. if you add more thinking it's low, it will blow overboard
    #5
    plugeye likes this.
  6. Sigean

    Sigean Adventurer

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    Apr 23, 2016
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    Devon UK
    Many thanks for this and I checked the return today, and saw the oil flowing. Not the flow I see from the return from my Rotax engine in my MT350 (like Niagara Falls....), but a good stream. Many thanks for the information, and drawing, very helpful.

    Kind regards,

    Sigean
    #6
    Beezer likes this.
  7. MrPulldown

    MrPulldown Long timer

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    A few more things about the oil and changing. There is a screen between the flex oil line and the frame at the front of the engine. This needs to be checked and cleaned out. I think the manual states with every oil change but. I use to do it every time, but after the first few I noticed that there wasn't any debris in the screen so I stopped. Also some aftermarket oil filters are too thick. This has causes come oil filter covers to crack on installation. Check your new filter thickness with the oil before installing. Not all aftermarket filters are bad.
    #7
    spacely likes this.