12.5 won't start?

Discussion in 'Mechanic and Repair' started by Shady Brook, Dec 26, 2001.

  1. awm

    awm LawnSite Gold Member
    Posts: 3,354

    i still tink it is just gummed up from letting oil run into everything.
    change the plug. let it set upright a day or so and use starter fluid to crank it. hope something works, good luck now.
     
  2. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Posts: 1,517

    You guys are just super!

    I have the head pulled as I type. There is oil in the cylinder, and on the top of the piston. Pretty messy, I can see how that oil would hinder combustion. Any other observations I should make, actions I should take at this point. Any ideas would be appreciated.

    As far as the timing goes:

    Starting with both valves closed and piston up in cylinder.

    Intake valve opens as piston comes down cylinder.

    Intake closes as piston heads up into the cylinder.

    Both valves are closed as piston comes down cylinder.

    Exhaust valve opens as piston goes up the cylinder, BUT does not close til the piston begins to come down the cylinder again, and simultaneously upon the closeing of the exhaust valve, the intake valve begins to open again, as the piston comes down the cylinder.

    The intake valve is open to it's fullest with the piston all the way down, and begins to close as it goes back up the cylinder again, and closes about half way up.

    The rest of the way up the cylinder, and all the way back out the valves are both closed.

    Does not seem to match with what Richard and cnflawn indicated it should. Help! :)
     
  3. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Posts: 1,517

    Is it possible that my timing has been off for a while? Could the mower start with this senerio, but be a hard starter. Mine has been very hard, sometimes 50 pulls even when it is warm out. I just wonder if that is the case, or if I cobbed it up when I changed the seal? How do I correct this?

    Thanks
    Jay
     
  4. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    It definately sounds like the cam timing is way off. The engine might run with the cam timing like this but if you could get it to start it wouldn't have any power.

    Your next step is to clean out any oil that you can and then head to the dealer and get a new head gasket.

    There should be a mark (like a round punch mark) on the gears of both the crankshaft and the cam. If when you rotate the crankshaft these marks do not line up then you need to line them up. The cam will pull out of the block but you may to push on the lifters a little to get it out.
     
  5. Robert Doubrava

    Robert Doubrava LawnSite Senior Member
    Posts: 342

    That's the mitake we made when we overhauled a 7HP B&S vert. We did not set the timing very well!! It didn't run very well at all.
    Well, good luck on your engine!!:)
     
  6. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Posts: 1,517

    Thanks for the support fellas.

    Seeing how I am going to have to take everything apart again, does anyone know the official torque pattern, and torque numbers I am to apply to these head bolts, and to the part pertaining to the sump area? Should I leave the head off when I go back to change the timing, or does it not matter to much at this point? I am thinking of redraining the oil, and pulling the muffler and carb. Boy this is really not as much fun as I had hoped for. :(

    Thanks
    Jay
     
  7. Robert Doubrava

    Robert Doubrava LawnSite Senior Member
    Posts: 342

    Well, I hope that it gets to be more fun for you. It wasn't fun for me when we overhauled that old Briggs. One thing you don't want to do is put that Lok-Tite grease on the head bolts!!;)
     
  8. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Posts: 1,517

    Thanks to all of you who spent time helping me through this problem!:blob3:

    Special thanks to Richard, and CNFlawn, who walked me through the timing process!

    I set the timing, put everything back together, 3 pulls later, my mower was running! :D :D

    After a million pulls on the rope, it turned out to be a timing problem. Boy is my sholder happy that she is fixed.

    Thanks a ton!

    Jay
     
  9. Robert Doubrava

    Robert Doubrava LawnSite Senior Member
    Posts: 342

    Your welcome. I'm glad to hear that you got it fixed.:) :) :blob3: :blob3:
     
  10. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    I'm glad it worked out for you.
     

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