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Thread: Timing chain trouble on a tare down

  1. #1
    Join Date
    Feb 2022
    Location
    Shakopee MN
    --
    42

    Timing chain trouble on a tare down

    I'm trying to do a tare down of a locked up 85 250es motor I got on a parts bike. I've never done this before, so forgive me if I'm missing something obvious. I need to get the timing chain off and I can't seem to do it. I took the tensioner off, but there's not enough slack to get it off. I also wasn't lucky enough to have the sprocket be in a position where both the retaining bolts are accessible. I was really hoping to do a top end rebuild only on this motor as I'm guessing it's locked up from sitting outside, but the only way forward I can see is to break the chain.

    Anyone have anything else I could try? Also, I watched a video of a 250sx motor tare down, that guy only had to remove the tensioner to get enough slack, is my motor weird or something?

  2. #2
    Join Date
    Feb 2022
    Location
    Shakopee MN
    --
    42
    I've been trying to use the search to find out more on what I can do here, but I'm not very good at using it yet.

    So far I've found a post that says while installing a new chain you have the cam sprocket unbolted to have enough slack in the chain. If my chain is not stretched out, this would explain why I don't have enough slack to take it off. Unfortunately, since I can't access both the sprocket bolts, and have no way of getting the piston to move, it looks like I'll be having to buy a cam chain breaker.

    Sound like I'm on the right track here or is there something else I could try?

  3. #3
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    Did you try turning the crankshaft back and forth at the flywheel ?
    I’ve run into this situation several times , the last one I was able to pick up on the back side of the cam and put it at an angle just enough to pry the chain off without hurting anything .
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
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  4. #4
    Join Date
    Feb 2022
    Location
    Shakopee MN
    --
    42
    I haven't tried that, but it sounds worth trying. I'm not too hopeful though, when I pulled the spark plug I could see the piston is rusty, I'm guessing this thing is locked up hard.

  5. #5
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    Put plenty of penetrating fluid down the plug hole to try and free up the piston
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  6. #6
    Join Date
    Feb 2022
    Location
    Shakopee MN
    --
    42
    Duplicated this post and got more traction on it here:

    http://www.3wheelerworld.com/showthr...e-on-tare-down

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