Anyone ever snapped a wrist pin?

Discussion in '2-Stroke Engines' started by Bzura, Mar 31, 2014.

  1. Bzura

    Bzura Member

    I hammered this out of a brand new (but heavily modified) GT5 66cc's piston.

    The engine ran great for about 5 minutes, and then there was a clunk & it seized. I was just warming it up, and only rode it to get it started. It was idling when it died. I expected to find one of the pin clips came out & jammed in the piston/cylinder, but the cylinder was undamaged & slid right off. A piece of the pin must have fallen down & locked up the crank because that won't budge. I haven't taken the bottom end apart yet to see what's up. I was extremely surprised to find the wrist pin cracked in half like this. There must have been a flaw in it.

    Anyone else ever see this?

  2. HeadSmess

    HeadSmess Well-Known Member

    warranty! just dont let em know you did anything ;)

    shrug, sigh, move on. thats just one of those things that happens and cant be avoided. and you didnt have to push it anywhere. unusual but! congrats!

    NOONE has shown a snapped pin before :)

    i wouldnt bother with the bottom end other than for parts. new crank will cost near as much as the engine anyway...
  3. jaguar

    jaguar Well-Known Member

    yeah that is really unusual
  4. Fabian

    Fabian Well-Known Member

    Crikey, how did you manage to do that?
    That's only ever happened to someone when they accidentally threw their bike into reverse; going 50 mph downhill
  5. HeadSmess

    HeadSmess Well-Known Member

    other than harley and goldwing im hardpressed to think of any bike with a reverse!

    couldnt happen in a goggggggo mobil :) reverse is simply running the (2stroke) engine backwards :)

    g oh, g-g, oh... ja, its the dart... :tt1:

    did it in the new car once when first changed from the old hiace with column shift, to a town ace with auto dashboard shift. hate new cars. cant even tell the engines stopped until you put your foot down and it just keeps getting slower!

    vote1 headsmess. no more luxury cars :) radio, aircon, padding...oh yeah :) gone. meant to be driving...i gotta go start a thread...
  6. desertsteve60

    desertsteve60 New Member

    CAM00013.jpg CAM00013.jpg I never had a wrist pin snap, but I had a titanium wrist pin do this (see pic) after only about 400 mi.
  7. Fabian

    Fabian Well-Known Member

    What was the oil/fuel ratio?
  8. desertsteve60

    desertsteve60 New Member

    Lucasoil semisynthetic @ 32/1
  9. Fabian

    Fabian Well-Known Member

    What is the carburettor main jet size?
  10. desertsteve60

    desertsteve60 New Member

    stock NT carb with original(70?) jet. The plug read a nice med brown. The only reason I even discovered it is that a ring caught on a port and broke and destroyed my CR Machine Stage 1 top end. Bummer.
  11. HeadSmess

    HeadSmess Well-Known Member

    here we learn why i stopped bothering doing anything :) they seem to last longer left alone. disheartening to port for 5 hours, 2 days, whatever, to find simple things like locating pins in the pistons have fallen out... run em and kill em i say :)

    oh. simple titanium test. grind it.

    i always read the spark was meant to be blue sort of colour, but hey...