what could cause this?

[chrisdoc0608]

Long story short, a guy from pwctoady brought me a ski to work on. It had what appeared to be an exhaust leak and the carb was not tuned. I spent days on it and couldnt find the leak so I just pulled the motor and then I found it. Two nickel size holes in the crank case. The guy just bought the ski from some other fourm member, and it actually runs like this. Im shocked and I can't think of anything other than it was existing and was patched then failed. Anyone else have an idea of what could do this and still have a running motor with near perfect compression?

 

[Cannibal]

Maybe foreign object got dropped in and the crank broke the smaller one out then actually managed to push the object out the bigger one??? Notice how the lower one is actually completely round like something was pushed through it?

That's the best I can think of.

 

[SurferSmurf]

maybe a 9mm round??? or 2

 

[cookerq62]

My buddy has an old race 750 from the bud tour days. It has no flame arrestors on it and he had this happen. He fixed it and continues to run the ski with no flame arrestors! It still ran like a champ He only noticed cus he replaced the motor mounts. This looks like job for JB WELD!

 

[chrisdoc0608]

I feel really bad for the guy that bought it. He is a cool guy and this was his first ski... the guy that sold it to him said the smoke that came from the motor ( the holes) was normal.... looks like he got screwed

Im going to tear into the bottom end tomorrow and see if anything is laying around. Hopefully I can get him back on the water soon.
I just thought this was really strange. I have never seen anything like that without some serious damage to the motor, but the thing actually runs.

 

[Cannibal]

Not really anything that would keep it from running. It would just run really lean. However, if someone richened it up a bunch it wouldn't be quite as noticeable. Still has to be really lean at higher RPM though.