Post by JerryScript on Nov 14, 2016 15:10:37 GMT -5
My nephew's Icebear suddenly stopped working last week. It made a bad noise from the crankcase, and would only start with lots of throttle and would not keep running.
I tore the top end down first, no issue with the head, jug, or piston, so I had to split the case. As soon as I it apart, I grabbed some oil from the inside on my fingers, and it was silver. I cleaned out at least a 1/4 teaspoon of very fine metal. Pulled the crankshaft, and the outer bearings were fine, though one did have a slight bit of drag. Grabbed the con-rod and found at least 1/8" play up and down. No damage to the rest of the internal parts of the engine, no wear or scrapes of any type. Looks like the con-rod bearing failed, so I'll be heading to Scrappy's tomorrow for a new crankshaft.
This Icebear has a 47mm BBK, which is generally not a big enough upgrade to cause crankshaft failure. My nephew does ride 2-up alot, giving friends rides everywhere, so it could have been stress, but I'm leaning towards a manufacturing flaw that finally failed after a year.
For those curious, it's ok to have a tiny bit of play side to side on the connecting rod, but up and down play is very bad. It can cause the piston to hit the head, and will make it appear as if you've lost compression, since the chamber area is larger with the con-rod able to move further back. Over time, it can shatter the skirt, or end up with catastrophic crankshaft failure, worst case blowing the engine.
I tore the top end down first, no issue with the head, jug, or piston, so I had to split the case. As soon as I it apart, I grabbed some oil from the inside on my fingers, and it was silver. I cleaned out at least a 1/4 teaspoon of very fine metal. Pulled the crankshaft, and the outer bearings were fine, though one did have a slight bit of drag. Grabbed the con-rod and found at least 1/8" play up and down. No damage to the rest of the internal parts of the engine, no wear or scrapes of any type. Looks like the con-rod bearing failed, so I'll be heading to Scrappy's tomorrow for a new crankshaft.
This Icebear has a 47mm BBK, which is generally not a big enough upgrade to cause crankshaft failure. My nephew does ride 2-up alot, giving friends rides everywhere, so it could have been stress, but I'm leaning towards a manufacturing flaw that finally failed after a year.
For those curious, it's ok to have a tiny bit of play side to side on the connecting rod, but up and down play is very bad. It can cause the piston to hit the head, and will make it appear as if you've lost compression, since the chamber area is larger with the con-rod able to move further back. Over time, it can shatter the skirt, or end up with catastrophic crankshaft failure, worst case blowing the engine.
% of the sites out there. Sprocket swap works though.
