compression release Briggs

Discussion in 'Mechanic and Repair' started by hotrodsnapper, Feb 8, 2007.

  1. hotrodsnapper

    hotrodsnapper LawnSite Member
    Messages: 85

    Hello All:
    With advice from khouse, restorob, stumper and a host of others I got that Briggs with the busted rod back together (m/n 28N7071036).

    Now that I have the motor cleaned up, filled with oil and set up on a test stand, I realize that my rather weak battery does no have the juice to crank the engine past the compression stroke. I suspect that the compression release is not operating. I should be able to get it started with the battery out of my car, my question is will the compression release likely free up after running for a while?

    Also, if it will not start working after running, is there a trick to get it to operate without opening the crankcase?
  2. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    A weak or bad battery and/or starter will give the symptoms of a bad compression release. Make sure both are good before you blame the release.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Just a reminder, These valves must be adjusted with the piston 1/4" down the cylinder past top dead center compression stroke. If it wasn't the comp. release will not function properly.
  4. hotrodsnapper

    hotrodsnapper LawnSite Member
    Messages: 85

    I hadn't even considered the valve adjustment. I remember my manual being a little ambiguous about crank location for setting the valves.

    It sounds like I should bring the piston to top dead center, then turn the crank a couple of degrees to move the piston 1/4" past TDC, which begins the power stroke.

    Am I understanding this right?

  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Here is a paste I saved a while back because I got tired of typing it, This should cover it.

    Remove the valve cover then rotate the engine over by hand until you reach top dead center compression stroke, Then remove the spark plug. Once at TDC insert a small screw driver in the plug hole touching the piston and rotate clockwise past TDC until you see the screw driver move down inside the hole 1/4". Now loosen the jam screw in the center of the adjustment nut and adjust to .005-.007" both intake and exhaust. Hold the adjuster nut with your wrench while tightening the jam screw. It may take a couple times to get it right because when tightening the jam screw it could throw the adjustment out so check after tightening.
  6. hotrodsnapper

    hotrodsnapper LawnSite Member
    Messages: 85

    I should have thought to run a search before I asked about the valve adjustment! Thanks as always, will provide update ASAP!
  7. hotrodsnapper

    hotrodsnapper LawnSite Member
    Messages: 85

    Here's an update for anyone with similar issues, although my situation here is pretty unique.

    I adjusted the valves per Restorob's procedure, but noticed that the intake rocker arm did not move at all during the compression stroke. At this point, since the engine was already sitting on my bench, I removed the oil pan and popped the cam out.

    The little weight was stuck in the running position, and the spring could not push it back to the starting postion. After poking at it for a few minutes, I removed the pin that the weight attaches to and rolled it on a flat surface and it became apparent that the pin was bent! The round side of the pin was rubbing against the camshaft hard enough that it could not This is probably due to the rod coming apart.

    Since this was later last night and my dealer was not open, I staigtened the pin with some hammer love. The weight and everything now moves freely and snaps into the start position without any trouble. I sealed the crankcase back up re-adjusted the valves.

    Where before I couldn't turn the engine through the compression stroke at all, now I can without much effort.

    One question though: I doubt that pin will hold together very long after I whaled on it with a hammer--can you buy the compression release assembly by itself or do you have to buy the whole camshaft? The engine numbers are:

  8. lucforce

    lucforce LawnSite Member
    Messages: 223

    Nope, The cam is sold as an assembly.

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