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  1. #1

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    OS 4 Stroke Cam Timming ?

    Does any one know how to set the cam timming on an OS 40 4-stroke. I am selling it on ebay and would like to at least have the cam timing set for the new buyer. I looked at my Enya 1.20 4 stroke and it is not even close. But that ones is complete and also on ebay.

  2. #2
    \"The weather is here, wish you were beautiful.\"
    J. Buffett

  3. #3
    Moderator Matt Kirsch's Avatar
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    OS 4 Stroke Cam Timming ?

    Since there is no ignition system, you got two shots at getting it right.

    With the piston at Top Dead Center (TDC), the mark on the cam gear should be either straight down or straight up.

    Once that's done, run it through a cycle and watch the valves:

    1. TDC: Both valves closed
    2. Down stroke #1: Both valves closed
    3. Up stroke #1: Exhaust valve opens
    4. TDC: Exhaust valve closes, intake valve opens
    5. Down stroke #2: Intake valve opens
    6. Up stroke #2: Both valves closed

  4. #4
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    OS 4 Stroke Cam Timming ?

    Sorry, the dot on the cam gear does NOT go straight up or straight down. It must be in line with the pushrods when the piston is at Top Dead Center.

    The instructions are on the O.S. Web site:

    http://www.osengines.com/faq/product-faq.html
    Bill Baxter, Manager Hobby Services/Futaba Service/North America
    3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
    Service Phone: 217 398-0007
    Email: hobbyservices@hobbico.com

  5. #5
    Moderator w8ye's Avatar
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    OS 4 Stroke Cam Timming ?

    Bax,

    There isn't anything on your web site about setting cam timing? If there is, it's not very apparent or easy to find?

    Set me straight,

    Jim
    Attended the CutFinger Institute of DirtNap University for years but never did graduate....
    Recipient, Mangledhand award August 2008
    Club Saito Member #7
    Original AMA #31261

  6. #6

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    OS 4 Stroke Cam Timming ?

    I found it about a third of the way down
    How do I set the timing on my OS single cylinder engine?
    We recommend you send your engine in for service rather than attempting to set the timing yourself.

    However, if you're REALLY comfortable working on engines, these steps will allow you to set the timing. If you are unsure how to complete any one of these steps, we caution you against disassembling your engine and recommend instead that you send it to our warranty and service center for non-warranty repair.

    The proper way to set the timing in all O.S. single-cylinder engines with the front camshaft is:

    Rotate engine so that the piston is at Top Dead Center.
    Locate the timing mark on the side of the cam gear.
    Insert the cam gear so that the timing mark is in a direct line with the center of the cam followers and the centerline of the pushrods. It is NOT at a 90 degree angle to the crankshaft. The angle will be slightly back.
    Replace the cam cover and you're ready to go!
    This should get your engine running well, if the timing was off. If it is still running poorly, be sure to send it in for service to avoid accidentally doing more damage.

  7. #7

    OS 4 Stroke Cam Timming ?

    yea...all that was in the 2nd post of this thread.
    \"The weather is here, wish you were beautiful.\"
    J. Buffett

  8. #8

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    OS Valve Timing

    Hey Guy's,

    Here is a tip you may want to try if your uncertain the cam timing mark is in the right spot? Don't quote me on numbers here. The .40 FS for example has 22 teeth on the cam gear, the crank has 11 for a 2:1 ratio. 360 degree's divided by 22 = 16.36 degree's for each tooth on the cam. The way I look at it, there is three ways of putting the cam in. One is right, two are wrong.

    Install the cam, (you have to rotate things slightly because of the helix of the gear teeth) if it's right, the mark will be slightly angled back and almost parallel to the axis of the push rods as previously suggested. Now if you remove the cam and advance it 1 tooth or 16.36 degrees, install it, you will see that it is totally out to lunch. Remove it and retard it 2 teeth (1 tooth to the other side of the correct position) and it will be totally out to lunch again. Remove it, advance it 1 tooth, install, and your back in business.

    Another suggestion, before you tear the engine apart, make a primitive degree wheel. Time it with TDC on the compression stroke & the mark on engine case. Rotate the crank through it's valve cycles placing marks for the opening & closing of each valve.

    Now after you do your thing with the engine and reassemble it, you have a reference to check your valve timing. If your out 1 tooth with the valve timing you should easily notice it. Before you start your engine that is. Good luck with rebuilds.

    Pat.
    \"The Lord Listens, but Money Talks.\"

  9. #9

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    OS 4 Stroke Cam Timming ?

    LOL I wonder if my Crane degree wheel will work? Just kidding. I build race engines for people on the side in drag cars. anything from mild to wild. My Chevelle was almost 1000 hp.

  10. #10

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    OS 4 Stroke Cam Timming ?

    DTK,

    Maybe you would like to use my 2 cent degree wheel to dial in your next RAT motor, guaranteed 100 horse improvement. I'll send it down,but you have to pay the Custom's Brokerage and postage. lol. Pat.
    \"The Lord Listens, but Money Talks.\"

  11. #11

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    OS 4 Stroke Cam Timming ?

    Dude this is not Canada. We don't worry about stuff like that I am from Toronto myself. And boy it sure is nice not paying
    exchange
    duty
    excise tax
    brokerage fees
    extra shipping
    pst
    gst
    Need I go on

  12. #12
    Moderator Matt Kirsch's Avatar
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    OS 4 Stroke Cam Timming ?

    Bax,

    I'm sorry, but when the gears are meshed, the timing dot ends up pointed straight up or straight down with the piston at TDC. I just rebuilt one.

  13. #13

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    Timing Mark ?

    mkirsh,

    Hold the engine at almost arm's length in front of you. You need a keen eye (just one). Now visualize a parallel line along the same axis as the push rods on through the center of the cam & timing mark to the root of the tooth the mark represents, it should come into perspective for you. If you just line up the mark with the root of the tooth it will appear to be perpendicular, or Straight up & down. The only other thing I can think of is rig-up the GP laser level if ya got one?

    Pat.



    DTK,

    No need Brother, No need..... I Can sum it up in three words...

    DEEP, HARD & REPEATED..........
    \"The Lord Listens, but Money Talks.\"


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