2000 40hp 3cy. Piston chipped on both sides in same place

[Chris Cole]

Hello forum,

I took apart my induction manifold to look at my reed assembly, because my carb looked like it was spitting at WOT. In neutral I can get this carb and cylinder to work, but WOT nothing. Anyway, the reeds look good, but when looking inside my crankcase I can see that my piston is chipped on both the left and right side, why is this. (See picture). I guess this is what is causing my problem. Anyone have any recommendation on what I should do next.

 

[Chris Cole]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

Bump... Help anyone??

 

[j_martin]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

It's overhaul time.

Overheated, softened aluminum doesn't hold back hot exploding gasses very well. It almost looks like a torch cut.

Sorry

 

[achris]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

Chris,

What exactly are we looking at here? I can't tell what's in the photo, is it piston skirt?

Chris..................

 

[Chris Cole]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

thanks martin,
achris you are correct this is the inside of the piston, the piston skirt. The image that you see is the edge of the piston touching the crankcase wall. The cut looks like this on both sides of the piston skirt. It looks like there was some kind of torch cut, like martin said.

 

[redjmp]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

I'm sure we are looking at the sleeve not the skirt.

 

[WillyBWright]

Re: 2000 40hp 3cy. Piston chipped on both sides in same place

Did the motor overheat? The sleeve can slip out of place. It can drop in the bore or it can twist in the bore. If it drops, the top piston ring catches and takes the top of the piston right off. If it twists, the ports don't line up anymore. If it twists far enough, the exhaust and intake gases mix. I think we have the latter.

What can you do about it (if that's the case)? You can disassemble the powerhead, put the block in an oven and heat it up. Temp? I dunno, but I'd take it in 25 degree intervals from 300 til it moves. Then twist the sleeve back in place and let it cool on its own. I can't guarantee it won't slip right back out of place the first time it warms up to operating temperature. But operating temp is a whole lot cooler than 300. I would NOT consider this a reliable motor.