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Hot!4P90HUB timing marks

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Orayen
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2019/05/15 23:46:15 (permalink)
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4P90HUB timing marks

I'm changing the pistons rings on a MTD 4P90HUB engine off a Troy-Bilt riding mower. After I got the cam shaft out I noticed that the timing mark on the crank shaft had worn off (I know this isn't a good sign). There should be two timing marks, one on the upper gear and one on the lower gear. The mark on the upper gear is clearly visible. I believe the mark on the lower gear should line up with the upper gear. If you zoom in enough on the picture you can almost make out a mark on the lower gear that lines up with the upper. Can anyone confirm that the two marks line up?

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    Roy
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    Re: 4P90HUB timing marks 2019/05/16 00:03:37 (permalink)
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    What does the second gear drive?
    Orayen
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    Re: 4P90HUB timing marks 2019/05/16 00:13:44 (permalink)
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    The second (bigger and upper) gear drives the balance shaft.
    AVB
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    Re: 4P90HUB timing marks 2019/05/16 07:37:37 (permalink)
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    The following image is from the P90 service manual with the timing marked in red. It appears the cam timing is off by two gear teeth to the right as viewed as in the image. I personally haven't been inside one these P90 yet but I do need to the crankcase cover on one the shop just it is not a primary project at this time. Customers comes first and first is one for a project later.

    Roy
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    Re: 4P90HUB timing marks 2019/05/16 11:48:52 (permalink)
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    Check the cam timing by rotating the crank until the piston is at tdc on the exhaust stroke. The exhaust lifter should be dropping as the intake lifts.
    Orayen
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    Re: 4P90HUB timing marks 2019/05/16 14:29:21 (permalink)
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    Thanks AVB for that picture. I think it's a little difficult to determine position from that picture because of the angle. I put a red dot on where I think the timing mark is and tried to recreate the picture. I think it matches. What do you think?

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    AVB
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    Re: 4P90HUB timing marks 2019/05/17 04:52:41 (permalink)
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    Does look right from here.
    Orayen
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    Re: 4P90HUB timing marks 2019/05/18 17:14:58 (permalink)
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    It runs!!

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    Roy
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    Re: 4P90HUB timing marks 2019/05/18 22:47:03 (permalink)
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