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  1. #41
    Join Date
    Aug 2019
    Posts
    2

    Default Re: Two-stroke conundrum

    Running well. Took home. Fixed leak. Wouldn't start.

    2 strokes are funny things. But concentrate on things that you have changed, in the order you changed them.

    Blockage in carb is high on your list. Something that has run in from the tank. Blockages in small carbs are very hard to find. An airline blow through is better than poking at things.
    Better to try real fuel than highly volatile fluids.
    I often find that heating the plug on a gas ring or with a blowtorch will get a motor going and (hopefully) it's OK after that. Always a a mystery.

  2. #42
    Join Date
    Apr 2005
    Location
    Shropshire
    Posts
    8,903

    Default Re: Two-stroke conundrum

    "2 strokes are funny things. But concentrate on things that you have changed, in the order you changed them." Good advice

  3. #43
    Join Date
    Apr 2011
    Location
    Me: Midlands, Boats: East Coast
    Posts
    370

    Default Re: Two-stroke conundrum

    Thanks for all the input, and apologies for not having been back for a while - for some reason my spam filter thinks YBW notifications are spam......
    The engine still won't start - the woodruff key is fine so timing must be ok I assume. I have had the carb apart again, poked through all the jets, sprayed carb cleaner through all the galleries I can see and blown compressed air up every orifice in sight. When spinning the engine with the drill and the choke on, the plug gets wet and there is no sign of firing.
    I will try heating the plug and putting it in hot before doing anything rash like taking the bottom end of the crankcase off to examine the reed and other shaft seal. Any idea of what sort of temperature? I can put it in an industrial oven at anything from ambient up to 1200C

    Thanks again
    De'il ding a divot auf yer wame wi a flaughter spade

  4. #44
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    20,428

    Default Re: Two-stroke conundrum

    100 degrees will be fine, although I'm not convinced that it will solve your problem. At least, you'll then have a chance of handing it with gloves on.

    If the engine spins easily, I'm not sure how much compression you have. A compression test would be helpful but if it spins at a similar speed with the plug out, then the compression is too low.

    Richard
    Last edited by RichardS; 01-09-19 at 11:22.

  5. #45
    Join Date
    Oct 2013
    Location
    Shropshire - Sundance, Bristol Channel
    Posts
    1,068

    Default Re: Two-stroke conundrum

    You shouldn't have to heat the plug, you're not going to do that every time you want to use it.

    Check the crank seal(s) haven't popped out, if it was me I would also whip the head off and look a bit deeper. I did have a 2.2 that was so salted up it cracked the head.
    Tom, Sundance
    2wheels1keel.com

  6. #46
    Join Date
    Apr 2011
    Location
    Me: Midlands, Boats: East Coast
    Posts
    370

    Default Re: Two-stroke conundrum

    Quote Originally Posted by RichardS View Post
    100 degrees will be fine, although I'm not convinced that it will solve your problem. At least, you'll then have a chance of handing it with gloves on.

    If the engine spins easily, I'm not sure how much compression you have. A compression test would be helpful but if it spins at a similar speed with the plug out, then the compression is too low.

    Richard
    The cheapo gauge I bought said 100psi with the engine spun by a drill
    De'il ding a divot auf yer wame wi a flaughter spade

  7. #47
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    20,428

    Default Re: Two-stroke conundrum

    Quote Originally Posted by Rum Run View Post
    The cheapo gauge I bought said 100psi with the engine spun by a drill
    That seems rather low for a quickly spun engine and would suggest a compression ratio of 7:1 although I would have thought that it would be enough to fire the engine if everything else was OK. However, it could be within the error limits of the gauge.

    I can't remember what else has gone before but if you've tested for a spark with a new plug and that all looks good, and spun the engine and found the plug wet with petrol, and removed and cleaned the carb, then I'm lost for ideas. I assume that you've tried starting with and without any choke as a wet plug will need no choke and some throttle opening to clear it.

    Perhaps try putting a ml of oil in the spark plug hole to temporarily raise the compression and try again. As already said, I would remove the air intake assembly and spray a little fuel directly into the intake to bypass any problem with the carb but I'm not sure whether you feel able to do that.

    Richard

  8. #48
    Join Date
    Oct 2013
    Location
    Shropshire - Sundance, Bristol Channel
    Posts
    1,068

    Default Re: Two-stroke conundrum

    Quote Originally Posted by Rum Run View Post
    When it ran before it seemed noisier than my Seagull Featherweight, which surprised me!
    Reading back, this may be your issue. I'm guessing inadequate oil mixture and it's semi seized in the past, but getting 100psi I would imagine it shout run.

    I notice you're in the Midlands? Where abouts? I'm in the motorcycle game and 2 strokes are my thing, if you're close enough. I always have a look?
    Tom, Sundance
    2wheels1keel.com

  9. #49
    Join Date
    Dec 2010
    Posts
    8,675

    Default Re: Two-stroke conundrum

    Reading this tale of frustration, I'm alarmed at the possibility that your Mariner 5hp is the same as mine (as yet untried).

    Does it look the same as mine, below?

    I'm keen to avoid ever doing what you did, which seems to have put yours to sleep. Where was the fuel leaking from?


  10. #50
    Join Date
    Apr 2005
    Location
    Shropshire
    Posts
    8,903

    Default Re: Two-stroke conundrum

    I've revisited this thread (but have not read every response) and it seems that you've tried all the usual problem areas: plugs (spark when out of the cylinder), fuel (plug gets wet), compression not too bad and the problem must be caused by repairing the original fuel leak. Another possibility is what I had on my BSA Bantam two stroke which was sometimes difficult to start especially if it didn't go first kick. It accumulates unburnt fuel in the crankcase. There is a drain plug and I found that removing it, kicking it over a few times to blow the fuel out and heating the plug allowed it to start and once started it would continue.
    You haven't said where the fuel leak was (unless I missed it) and how it was cured but could that have caused starting difficulties?

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