Cant maintain TDC for valve job
  • robobob
    Posts: 3
    Joined: Sun Jun 14, 2015 1:56 pm

    Cant maintain TDC for valve job

    by robobob » Tue Feb 06, 2018 11:15 pm

    Hi - long time lurker - first time poster... :)

    I recently finished a successful valve job on a CRF230F and decided to do the other bike (CRF150F) right away because I already had all the right tools and such out. Ha. Well, my surprise is that on my 150 when I use the crankshaft nut to find top dead center, right after I see the "F" for "firing" in the sight hole and I'm ready to turn a little farther to get "T" to "top", the motor wants to slip past the "T" rather than letting it stop at the "T" point. The 230 didn't act this way. It was happy to stop at the "T" for me. On the 150 I found this behavior both on the compression and exhaust strokes. I could have a helper hold it at "T" for me, but I'm wondering if this is a sign of something else. Thoughts?

    [BTW, the reason I"m wondering about other possibilities is that while the 150 runs fine at least when it's warm, I find that when it's near idle and cooler that sometimes I hear it "stutter" when I'm just adding a tiny bit of throttle above idle. The stutter is pretty pronounced and seems like the engine isn't very happy - but as it warms all seems fine.] Dunno if this is a typical kind of behavior or if it might be a sign of a timing chain issue of it being stretched or slipped/skipped and if the above symptom is just another thing pointing to that problem.

    Thanks!
    bob
  • Aussiecrf230
    Posts: 1964
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: Cant maintain TDC for valve job

    by Aussiecrf230 » Fri Feb 09, 2018 3:14 pm

    Hi Bob,
    Have you tried getting it to stay at TDC with the plug out. I see you tried it at TDC on exhaust stroke so it shouldn't be flywheel is out and pushing piston back down.
    You are in neutral?
    You may have to pull the cam cover off to see what is happening with tensioner.
    Also make sure the piston is at TDC when mark is aligned.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas

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