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twiztidpod

engine wont start

twiztidpod
11 years ago

I am working on a briggs and stratton oppossed twin model 402707 the 16hp version. it has been sitting awhile but i have cleaned carb, changed oil, and installed a new battery. currently it cranks over well, gets spark to the plugs, and seems to be getting fuel in the cylinder as well, i have pulled the plugs adjusted gap to .30 and dried them off, then after cranking checked the plugs. they were wet with fuel. Out of frustration i sprayed starting fluid in the carb, still did nothing. When I press my palm over the top of the carburetor and crank it, it feels like it has really good vacuum, so i do not think it is a valve problem. does anyone have any ideas of what to check ??? Thanks in advance.

Comments (8)

  • walt2002
    11 years ago

    I would remove the cooling shroud, flywheel screen, flywheel nut and washer the see if you can look down the flywheel keyway and see if it lines up with the crankshaft keyway.
    Sheared flywheel key if not.

    Walt Conner

  • twiztidpod
    Original Author
    11 years ago

    Ok Walt, I'll check that. i went out to the shop after my last post didn't do anything to it. it started, ran about 10 seconds until i tried to give it some throttle, then it died and i cannot get it to start again, now i am going out to check flywheel key as Walt suggested, i will post an update after that.

  • twiztidpod
    Original Author
    11 years ago

    I removed the shroud to check the flywheel key, it was still aligned and looked good. since I had the shroud off I decided to clean up the coil. I lightly sanded the coil and the flywheel and cleaned up the magnets, which I didn't think needed doing since I had spark to both plugs already. Then I re-adjusted the flywheel gap to 5 thousandths. I put it all back together and it fired right up and runs really good. I didn't really do anything but it runs now. What Happened ??? I already had spark !!!

  • mownie
    11 years ago

    ***" What Happened ??? I already had spark !!!"***
    Naw, you just think you had spark.
    Checking for spark by connecting a spark plug lead to a spark plug and watching that plug for spark OUTSIDE of the combustion chamber is not always a guarantee that the spark will still occur in the combustion chamber under compression.
    Briggs recommends using their spark tester so you can watch for a spark while the plug is installed.
    The spark tester mounts onto the plug and the spark cable connects to the tester. Then you crank the engine and watch the spark tester gap for a spark. This device accounts for the change of resistance due to compression and will not give a false sense of security regarding the ignition coil (magneto). Another plus you get using their tester is that you can run the engine on all cylinders and watch the tester to see if you lose spark during any mis-fire events (if that's what you're chasing).
    With 2 testers you can check both cylinders at once, if using just 1 tester you'll have to swap it to the other cylinder to test it.
    Other than that, the Briggs Opposed Twins Magnetron ignition system is about the only problem they have.

  • twiztidpod
    Original Author
    11 years ago

    WOw thanks Mownie, I was just under the presumption that if i seen spark outside the cylinder then I had spark inside as well, that spark tester sounds like a good tool to have. i'm going to check it out.

  • mownie
    11 years ago

    1,000 words.

  • baymee
    11 years ago

    Isn't .005 coil air gap too small?

  • mownie
    11 years ago

    Yes, .005" is a bit close, but I wasn't the one using the feeler gauge so I don't know if it is actually on .005" or a bit wider :^)
    Briggs specs call for .008" to .012". Typically folks set them about .10", or the thickness of a common business card.
    Used to be called "the thickness of a match book cover" but nobody knows what the heck matches are anymore.

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