Engine Trouble Did I wreck my bike already?

Discussion in '2-Stroke Engines' started by Clancy, Jun 22, 2014.

  1. Clancy

    Clancy New Member

    Hey folks,
    Just bought this motorized mountain bike 2 days ago. So excited, runs well and got me to work in minutes today!

    Thing is, I am quite foolish and forgot to close the fuel line when I went into work today. When I came out 4 hours later it was pretty much dry. I then proceeded to ride it home (which I now have been told was a terrible idea), and towards the end of the ride it got pretty weak, sputtering like and giving me no power, like it was running out of gas. Now its only running when the choke is all the way on, but its super choppy, and i feel like I'm not getting all the power it started with.

    Did I f*** this one up bigtime? Someone mentioned a seized engine, don't really know what that means.

    Any help would be really appreciated!

  2. crassius

    crassius Well-Known Member

    could be a lot of things - air leak because carb isn't tight, leaking head gasket, blown crank seal

    none of the above is a serious problem, but you'll need to look around the board here for info on checking & fixing these things - you might also just check with the guy that built it
  3. Redbiker

    Redbiker New Member

    What is your fuel mix ratio? Is everything sealed tight? Is there leaks or cracks on close examination?
  4. HeadSmess

    HeadSmess Well-Known Member

    pretty well much dry...

    so, it was empty when you started?

    of course it ran out of fuel!

    when they do that, unless jetted spot on already, they will tend to get a lil bit faster! then splutter splutter, cough.. one last vroooooom, then...start pedalling :)

    but. if its misbehaving now you have more fuel in it.... right.

    debris in the bowl of the carb/ blocked jet. that would explain why it needs full choke. and of course, seeing as the choke reduces a 16mm hole down to a 3mm hole, it wont make much power with the choke on :wacko:

    so, thats an easy fix. pop the carb, clear the jet, and re tweak the floats so that you dont have to turn the fuel off anyway! cus straight away, if it drains itself when forgotten about, it has an issue. an annoying one. easily fixed, mind you :)

    it turned over nicely despite having drained all the fuel out while standing? where did that fuel go? cus normally, it dives straight into the crankcase, that then blows the crank seals (usually the skinny one behind the magneto) when the owner, unbeknownst, pedals away then dumps the clutch and all that fuel has nowhere to go in a two stroke but out the point of least resistance...the crank seal. :freak:

    just pop the (front) left hand cover and check for oil/fuel in there. none, breath a sigh of relief :)

    a popped seal will prevent it running nicely.

    whoever said the engine is seized (there are more exceptions to the "i" before "e" cept after "c" rule than words that use it)...go up to them tomorrow, and give em a smack round the chops! i dont see any evidence of them being on this forum, so you should be able to smack em :jester:
  5. butre

    butre Well-Known Member

    the fuel evaporates when it's just sitting in the carb, but the oil stays. makes starting a complete ***** when you forget to shut off the fuel.

    My bike is living proof that a blown crank seal isn't a huge deal, you've got something else wrong with yours.

    are you absolutely certain it's not out of gas?
  6. HeadSmess

    HeadSmess Well-Known Member

    and walking 20km home the other day was living proof that one worn crank seal can prevent running. roll down a 25 degree hill, thats 700metres long without even a splutter? and then followed by the 4km downhill through the nasty lil road (goat track) that heads back home.

    but then started first go after replacing it this morn...

    oh, sure they will run...the issue is getting them going in the first place.
  7. butre

    butre Well-Known Member

    mine starts fine, I just have to let the oil out of my magneto side every once in a while. I've got spare parts for when it finally does break, and a couple good friends who own trucks for when I get stranded.

    of course a badly blown crank seal is another matter, but in my experience they don't go like that very often.
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