engine exploding?

Discussion in 'General Questions' started by Werdna, Mar 28, 2007.

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  1. Werdna

    Werdna Guest

    With my 70cc engine and the 44th sprocket that comes with dax's kit, with full throtle can I go fast enough on flat ground that the engine would explode or something like that? If not, how far does it have to be pushed for it to explode?


  2. Thejman

    Thejman Guest

    only thing I know that would explode these motors would be NOS.
  3. Werdna

    Werdna Guest

    uhh...what is NOS? :? I'm feeling uneducated!
  4. Guest

    Guest Guest

    That or running too lean.

    NOS is nitrous oxide, a gas that oxigenates the fuel. You need to run a solenoid to allow more fuel to be admitted to the carb if you run NOS.

    It's for race cars, not little bike engines, and not really good for two stroke engines of any kind. Less than scrupulous folks sell "NOS kits" on ebay.

    Run away screaming!

    You shouldn't be able to blow the engine by running it in the stock configuration with the factory supplied sprocket.

    Make sure your intake gasket is in good condition as they tend to leak air after awhile. Leaking intake gaskets (among other things will make the engine run lean....
  5. yea mine does the same too, it seriously screams! i thought i would blow it up too! not to mention that the seat vibrates like crazy! but i hear these 2 strokes like to run like that. i abuse mine like crazy and it hasn't given me any problems!
  6. gone_fishin

    gone_fishin Guest

    it can't hurt itself...as bikeguy sez, optimize the stock configuration and go for it :evil:

    (always be on the lookout for top-end 'surging'...a clear sign of an intake leak & lean conditions, not cool)
  7. rcjunkie

    rcjunkie Guest

    You may damage your engine if your go full throttle downhill. The cheap chinese metal connecting rod may not be able to handle overrevving while downhill. Should not be issue on straight away or up hill.
  8. Guest

    Guest Guest

    True, but you'd almost be asking for a meltdown if that were the case.
  9. rcjunkie

    rcjunkie Guest

    I'm not sorry, but I can't let your statement stand without questioning its basis. A meltdown? What in the world are you talking about?

    The con rod is under tremendous stress from the reciprocating load represented by the piston, actually stretching and relaxing with every rotation, and the load increases rapidly with increasing engine speed. Failure of a connecting rod is one of the most common causes of catastrophic engine failure. It is often considered an engine's "weakest link".

    So, could you repay the favor and explain what you mean by "meltdown". If you were emplying engine seizure, overrevving won't necessarily do that unless it overheats from being run too lean.

  10. Guest

    Guest Guest

    Sorry for any misunderstanding....

    I'll put it another way.

    I one were to run one of these admittedly old-tech engines downhill long enough and fast enough, running at redline or above without a perfect mixture, it would encounter some form of catastrophic failure. Otherwise know here in north east Ahia as a "meltdown". (although not the type experienced by many folks in Holly-weird)

    Could be in the form of a snapped rod, bearing failure, ring or piston skirt breakage, seizure, ect. In other words, you turn your engine into a small pile of inexpensive scrap/tears/swearing/capital loss.

    If one were to run one that hard, they should not be surprised or upset when the whole thing goes "kablooie" :eek: :( (tech term there). :D

    I didn't mean the engine would literally "melt down" that would take a lean run of about 30 seconds at which point the aluminum would turn to clay (once again not literaly) and melt....I've seen it in many two stroke engines.
  11. Guest

    Guest Guest

    You've never seen a piston with a hole melted through it? It only takes a short run with a mixture that is too lean to melt a piston dome.

    No matter how much oil you use in the mixture.

    Ultralight aircraft have an EGT (exhaust gas temp.) gauge to monitor the internal temps. When running WOT at take off, they run somewhere around 950-1000 degree F. At cruise, they run around 1000 1050 degrees. A very short run at 1300 (due to a lean mixture) will result in a holed piston, or at least melted ring lands, which in turn causes high heart rate, loud explatives from the pilot, and most times, other damage to the aircraft.

    What I'm trying to say in laymans terms is-
    "If you run downhill, wide open, engine screaming, long enough, expect the worst."

    ie "asking for a meltdown".
  12. srdavo

    srdavo Active Member

    also...on kinda an opposite thought. you probably shouldn't get off the throttle completely on a long downhill with the clutch engaged. your engine will still be spinning fast with very little fuel/lube running thru it.
    anybody have any thoughts about this?
  13. Guest

    Guest Guest

    You are coorect sir!

    With any two stroke running pre-mix, one should always open the throttle slightly every couple of seconds while on a long downhill run.
  14. rcjunkie

    rcjunkie Guest

    Thanks for the info regarding the term meltdown. I agree that running lean or low on oil can cause this problem. I'm not sure if meltdown will occur at full throttle on a downhill assuming mixture was correctly set in the first place.

    The type about blipping the throttle on a long downhill is pretty good to ensure that the internals are getting enough fuel mixture (which contains the precious lifeblood called 2 stroke oil mixed in with it).

    I run EGT gauges on both of my turbocharged vehicles. My EGT is higher at lower rpms when load is very high and engine is straining to maintain speed or to accelerate. It is a little lower when acclerating hard at high rpms at full throttle and full boost.

    If someone has an infrared temp guage, they should check their cylinder head temp(right next to spark plug). You should strive for a max temp range between 250-275 deg F. Any higher would shortern engine life and lower is usually better.