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Thread: Finding Top Dead Center--any tricks?

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  1. #1
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    Finding Top Dead Center--any tricks?

    ON my 2009 r1200r, finding TDC has been a challenge. That arrow that shows up so well in pictures doesn't show up so hot in real life on mine. It's there, barely visible, but it is almost a 2 person job. I tried putting a dot of paint on it, but the paint was washed off by oil. It certainly does not jump out at you.
    Two questions: are there any tricks to getting TDC, other than turn the rear wheel a little, look and feel the valves, repeat...

    and

    Can you assume the engine is TDC IF BOTH valves, exhaust and intake are loose. IOW, once any clearance is there, is the engine at TDC? It seems that they are either loose or they're not, no middle ground.

    Thanks

    John

  2. #2
    Nickname: Droid
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    It has never failed me to rely on both intake and exhause valves being loose, and timing indicator on the flywheel (or wherever) to be at TDC, to properly indicate that cylinder at TDC on the compression stroke.

  3. #3
    Cam Killer marchyman's Avatar
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    There is middle ground... the cam is smooth, not stepped. There is also a large range (don't remember the exact number of degrees) where both valves are fully closed so if you are off a bit you are likely OK. I had no problem seeing the arrow on my GS with enough light. A flashlight when looking for TDC helped. Here you can see the arrow in the flash of the camera. It looks the same when using a strong flashlight.

    p-20110125-1431-2696.jpg

  4. #4
    Benchwrenching PGlaves's Avatar
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    On Airheads and Oilheads I always just pulled the plug out of the timing hole cover and looked for the TDC mark. Did they omit the timing hole on the Hexhead?

    p.s. After chasing my tail a few times trying to line things up with the rear wheel I also almost always just remove the front cover and turn the crank with a wrench while I watch the flywheel through the timing hole.
    Paul Glaves - "Big Bend", Texas U.S.A
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  5. #5
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    Yup, different system and no rubber plug to accidentally lose down the rabbit hole when putting it back, either (I stick mine on an ice pick when positioning on oilheads).

    Re the TDC on the hexhead, as was noted, all you need to do is get reasonably close. Cam max durations are in the 270-280 degrees range on any gas engine with most all of the lift occurring in the middle half of that spread. The rest of the 90 degrees of the cam is no lift so as long as both valves are loose and you're somewhere generally in the middle of that wide degree range you're fine. No need to obsess about exact TDC just to check a valve clearance- getting it to the nearest degree won't do a darn thing for your valve adjustment one way or the other.

    An old trick for getting closer without depending on those hard to see marks on hexheads is simply to pull a plug and put a plastic straw down the hole to touch the top of the piston. When its at max extension you've found TDC.

    Its easiest to rotate the wheel . motor with the tranny in 6 if that's your choice for turning stuff..

  6. #6
    not so retired henzilla's Avatar
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    No timing hole...the arrows are visible only on one side...there is a plastic fan blade on the right side ( I am 50% sure it's the right anyways) that blocks it now...on some there is a square block on the gear that is in the position of the arrow. I just did Helen's '07 R12R and going by heatstroked brain at moment.

    I remove all four plugs anyways to take a look, so spinning the rear wheel in 6th and peeking for the left arrow has always worked for me
    Steve Henson
    SABMWRA MOA Club#62's Flat Fixer/ current forum moderator
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  7. #7
    Small road corner junkie pffog's Avatar
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    Pull a plug, stick a screwdriver in the hole and feel the piston, while bumping with the rear wheel.
    2010 F800GS Full Ohlins package, '04 R1100S Replika
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  8. #8
    Registered User mpmarty's Avatar
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    I use a 6mm wooden dowel in the horizontal spark plug hole.
    Marty - in the western Oregon mountains.'06RT, (gone '04RT, '86 Venture Royal, '81 Yamaha Virago920, '82Suzuki GS1100GK, '76 Suzuki GT750, Triumph 750 Bonneville, BSA Road Rocket 650, 61" Harley knucklehead)

  9. #9
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    Seeing the mark

    You may wish to try a different paint. There is a type called "ball paint" that is impervious
    to oil. My mentor always called it "junkyard paint" as it's what salvage yards use to mark parks.
    I mark all sorts of timing marks with it on equipment I repair. HF is where I get it, comes in an applicator, but I usually use a Q-tip. It is pretty permanet so be careful.
    Will Stagg Central Coast of Commiefornia
    2012 R1200RT (most awesome unit)
    1978 R100/7 (sidecar tug )
    Yamaha TW200 adventure bikes (3) waay fun units

  10. #10
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    Quote Originally Posted by mpmarty View Post
    I use a 6mm wooden dowel in the horizontal spark plug hole.

    I use a chop stick.
    Marty Hill
    12 GS black/Boxer Cup Replika

    ride till you can't

  11. #11
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    +1 and feeler gauge advice

    Chopsticks and both sets of valves are loose.

    2 more cents. Get the Wurth feeler gauge set from Beemer Boneyard. Using 2 lightweight gauges on the tappets of both valves simultaneously gave much more consistent results than using a single automotive style guage on one valve at a time.
    Eric * Columbia SC
    Piedmont Red 2006 R1200RT

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