It is called a wrist pin (I don't know why the "W") or gudgeon pin in some countries.
Too long to fit between the clips or doesn't fit the diameter the hole?
I have had this happen, both cases.
Sometimes quality control is not all it should be and I have received a wrong pin for my piston before.
Check, check, check...
If it doesn't push into the hole like the old one came out, that may not be a problem.
They are sized for a close fit, and if you held the pin in your hand for a while, it will heat up and not go.
Drop the pin in the freezer and warm up the piston gently with a propane torch just hot enough you can still hold it.
Get everything ready (one clip in, needle bearing in place, rag around rod and crank) and slide the pin into place.
Remember that the pin will be just as hard to remove once temperatures are balanced, so don't mess up.
Put the other clip on and you are done!
Steve
