Starting problems with a Howard 400 (sigh)

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  • April 16, 2016 at 6:19 pm #20528
    vhgmcbuddy
    Member

    Hi folks…. a couple of weeks ago I got my rebuilt JAP back (and I heard it running too)…. have now got it bolted back on the front of the Howard and the darn thing won’t start. I’ve got a nice big spark (the best I’ve ever seen that mag produce), if I really wind it up I get an occasional polite cough that goes with the spin. The timing of the spark seems correct, the impulse is triggering just after TDC. There’s fairly fresh fule in it (that my Honda engines seem to run on happily enough).

    All I’ve done to it since it got home is put an air filter on it and sorted out a throttle cable .

    I’ve tried EZ-start, I’ve tried putting a bit of fuel down the plug hole and I’ve even tried putting EZ-start down there too…. nothing has worked so far…. occasional polite cough forwards… I’ve tried it with the plug that went on during the rebuild (a slightly odd looking long-reach thing as well as with a new old-stock Champion L10 (which was specced for the engine). THe Mag had a new condensor fitted as part of the rebuild and, two weeks ago or so, started ridiculously easily once I’d sorted the timing out to have the impulse kick in after TDC…

    I did have to take the carb off to refit the aircleaner (the bracket is clamped by the two pieces of the inlet manifold), is there something drastic I can do to a Zenith 24T2 just by taking it off and on again?…. but then surely the @fuel down the plug hole@ trick would have worked…..any advice welcome

    chrisc

    April 16, 2016 at 6:21 pm #20529
    vhgmcbuddy
    Member

    Engine is a JAP 4/3, mag is a Wipac CJ936..

    April 16, 2016 at 11:16 pm #20538
    stuart
    Participant

    Providing the compression is good and theres fuel in the cylinder and the spark is at the correct time then it should go.Are you 100% certain the ignition timing is correct and the carb is in good order ??
    My 400 with the same JAP 4/3 engine fitted only needs a pull up on the starting handle and she,s away.

    April 17, 2016 at 3:13 am #20541
    vhgmcbuddy
    Member

    Unless something has shaken loose in transporting it home. The timing on the mag hasn’t changed, The spark is easily visible in sunshine, and i havent touched the mag since I started it at the rebuilders place. Weirdly I know way more about how to set the mag up than I do about the carb. That Zenith 24T2 is hard work for me to figure out, and it is only recently i stopped thinking of it as witchcraft. There is good compression, pulling it through you certainly know which cycle is which. I’ll pull the head off and check the timing properly, i’ve got a spare head gasket at home… The carb was cleaned during the rebuild, the engine was running before it, but lacked power, when I started it a couple of weeks ago it sounded crisp, and didnt smoke, unlike previously.

    April 17, 2016 at 8:31 am #20542
    charlie
    Keymaster

    Is there an air leaf where carb bolts on, you say you took it off. My old Trusty had the same carb and to start it I had to hold my hand over the air inlet, with air filter disconnected, this made sure it pulled plenty of fuel through.

    April 17, 2016 at 9:14 am #20546
    stuart
    Participant

    I had to file the manifold gasket surface flush on my Zenith carb as they do tend to “warp” from incorrect tightening / general misuse.Im sure I also fitted a couple of gaskets just to be sure there were no air leaks.My brass throttle spindle needed building up as it was quite worn / sloppy in the upper carb body.I just soldered it and smoothed it round with emery paper strip.Works a treat :).Apart from servicing the magneto and honing the cylinder bore and recutting the valve seats no other work was needed.I haven’t used the 400 for a couple of years as its buried in the back of the shed.They are excellent machines 🙂

    April 17, 2016 at 12:36 pm #20547
    vhgmcbuddy
    Member

    There’s a thick new gasket on the mating surfaces of the inlet manifold and it looked in good order, though I may well try taking off the air-filter stem and bracket and putting the air filter directly on the carb, one less source of airleaks in the inlet tract I guess… I suppose if there’s a leak there then closing the choke actually makes the situation worse as it will pull more through the leak…

    April 18, 2016 at 3:46 pm #20581
    charlie
    Keymaster

    Air leak on air filter side of throttle butterfly should not affect starting it is leaks from butterfly to engine that will be a problem, eg weaken the fuel / air mixture.

    April 18, 2016 at 8:16 pm #20602
    roatavator
    Participant

    Sorry to suggest something so simple, prompted by your description of “polite cough”. Are you sure the throttle is open far enough and operating properly on the carb end?

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