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Thread: Help Please!

  1. #1
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    Default Help Please!

    I built a hovercraft a couple of years ago. It has a Rotax 2-stroke engine that had to be rebuilt. Stupidly, I didn't start it for 6 months and now it will not fire up. Fuel seems to be getting through but the spark seems intermittent and weak. I am in South Woodham Ferrers, near Chelmsford. Anyone got any ideas or a contact for local mechanic who I could contact to try and sort this out???

    Any help would be appreciated.

    Thanks
    Chris

  2. #2
    Very active > 100 posts Club Member
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    Default Re: Help Please!

    Check the plug gap is correct - from memory the markings on the cowl are in mm not thou - I had hells own trouble with mine after a plug change until I tried gapping to the metric setting - and away it went! Just hope it is that simple!!

    Ross

  3. #3
    gaz
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    Default Re: Help Please!

    at the risk of pointing out the obvious… new fuel, clean carb of all old fuel and that gel that appears when you don’t drain out the fuel prior to storage !!!

  4. #4
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    Default Re: Help Please!

    don't take it to a local mechanic a bike mech would be more suitable.

    is it points or electronic ignition?

    if stood the points, likely need a little clean.

    check the grounding wires, to the kill switch.

    once you get a good spark it would not hurt to clean out the carbs, and ensure the choke plunger fully retracts.

    http://www.ultralightnews.com/enginemaintenance/

    this will help, have a read
    Jon

  5. #5
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    Default Re: Help Please!

    Replacing fuel and cleaning the float bowls goes without saying as previously mentioned.

    If points ignition, then clean the points (as already mentioned),use a bit of acetone on a rag wrapped around a feeler gauge blade.

    If electronic ignition the spark is always weak and difficult to see.

    Try a splash of fuel on the air filters as a starting aid, if no firing occurs, take chokes off and hold throttle fully open and try starting several times, it should cough and splutter before firing up fully.

    I hope that helps, let us know how you get on.

    Regards,

    David Kemp
    If in doubt, go flat out!

  6. #6
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    Default Re: Help Please!

    Cheers all

    Using new Fuel

    is it points or electronic ignition?
    Points I think

    if stood the points, likely need a little clean.
    I'll have to have a look and find these!

    check the grounding wires, to the kill switch.
    Hhmm, not actually fitted the kill switch yet!

    once you get a good spark it would not hurt to clean out the carbs, and ensure the choke plunger fully retracts.
    All seems to be working ok but I'll look at the carb and see how I can take that apart and clean it. Some fuel seems to be getting through to the plug. I think it's the lack of spark causing the problem!

    It's a NGK - R BR8ES plug. Looks like the gap should be .015 of an inch. I'll check that.

    Thanks to you all for your advice. Looks like my weekend is sorted!

  7. #7
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    Default Re: Help Please!

    Quote Originally Posted by cwells2 View Post
    Cheers all

    Using new Fuel dont forget the oil

    is it points or electronic ignition?
    Points I think

    if stood the points, likely need a little clean.
    I'll have to have a look and find these!

    the points are behind the pulley, within the fly wheel. you could really do with a rotax cooling fan holder, which will stop the fly wheel moving against the friction of the pulley to the cooling fan, via the belt.
    Remove the pull starter, if points it will have a box on the front of the pull starter housing. 3 off, m8 cap head screws hold the fan pulley to the fly wheel, under which you can see and clean the points thru the windows in the fly wheel.

    check the grounding wires, to the kill switch.
    Hhmm, not actually fitted the kill switch yet!

    how do you stop it? please don't say turn the fuel off!

    once you get a good spark it would not hurt to clean out the carbs, and ensure the choke plunger fully retracts.
    All seems to be working ok but I'll look at the carb and see how I can take that apart and clean it. Some fuel seems to be getting through to the plug. I think it's the lack of spark causing the problem!

    the carbs and chokes on these engines need to be correct, clean etc etc. but it should at least splutter if getting fuel.

    It's a NGK - R BR8ES plug. Looks like the gap should be .015 of an inch. I'll check that.

    sounds like the correct plug to me.

    Thanks to you all for your advice. Looks like my weekend is sorted!
    jon
    Jon

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