Busted cases

[Quingquad]

Thougt this would amuse you all... I bought a cheap blaster a few months ago. Did some cosmetic work to it and got it running. I barely got it to idle with the choke on, screw all the way in and a 360 main jet (outrageous). Looked at the enegine all over for leaks untill I found a small line crack at the bottom of the engine where oil was bubling out. After getting over the dissapointment I got some energy to open up the bottom end and this is what I found:

What could cause something like this to happen?

 

[yamaha28]

Piston skirt breaking off and dropping down into there, crank made some more room to accommodate. Same thing happened to my engine when I got it. sicivicdude repairs cases specifically for that kinda thing happening. I bet he will drop by tomorrow and let you know what's up

 

[Blaaster]

Thougt this would amuse you all... I bought a cheap blaster a few months ago. ?

I hope you got it real cheap, another example of blow it up, bandaid fix, and re sell.

 

[sicivicdude]

Thougt this would amuse you all... I bought a cheap blaster a few months ago. Did some cosmetic work to it and got it running. I barely got it to idle with the choke on, screw all the way in and a 360 main jet (outrageous). Looked at the enegine all over for leaks untill I found a small line crack at the bottom of the engine where oil was bubling out. After getting over the dissapointment I got some energy to open up the bottom end and this is what I found:

What could cause something like this to happen?

It's exactly as yamaha28 said, generally excessive piston to cylinder clearance from running an engine ragged (long past when it needed freshening up) letting the piston slap around inside there and breaking the skirt off. It falls (as gravity would have it) down into the bottom end and gets caught between the crankshaft and crankcase. Not all that uncommon an occurance unfortunately... and generally preventable with proper maintenance.

The bad news is, you can't run it like that. The other bad news is, most machine/welding shops won't fart with cast aluminum. It's not worth their time and energy to mess with it as it takes a lot more prep work and some special materials to work with. The good news is, that sort of damage IS repairable. If you do happen to know someone locally who does A/C tig welding (heliarc if it's an older person ) they can mess with it long enough to "figure it out" usually.

If not, shoot me a PM. I have case sets already repaired waiting for exchange.

Piston skirt breaking off and dropping down into there, crank made some more room to accommodate. Same thing happened to my engine when I got it. sicivicdude repairs cases specifically for that kinda thing happening. I bet he will drop by tomorrow and let you know what's up

Good job young padawan. You know I "sniff out" all of the "broken case" threads

 

[Prime]

I've had a set of cases like that before. sicivicdude does a great job repairing them.

Here's a before and after.

 

[sicivicdude]

^^^^ And that's not an exchange, that's the same case actually...

I have cases already finished I can "trade out" if need be.

 

[Shawn]

nice fix 15151515

 

[Budget_Blaster]

Damn bro you did a kick ass job!

 

[yamaha28]

It's exactly as yamaha28 said, generally excessive piston to cylinder clearance from running an engine ragged (long past when it needed freshening up) letting the piston slap around inside there and breaking the skirt off. It falls (as gravity would have it) down into the bottom end and gets caught between the crankshaft and crankcase. Not all that uncommon an occurance unfortunately... and generally preventable with proper maintenance.

The bad news is, you can't run it like that. The other bad news is, most machine/welding shops won't fart with cast aluminum. It's not worth their time and energy to mess with it as it takes a lot more prep work and some special materials to work with. The good news is, that sort of damage IS repairable. If you do happen to know someone locally who does A/C tig welding (heliarc if it's an older person ) they can mess with it long enough to "figure it out" usually.

If not, shoot me a PM. I have case sets already repaired waiting for exchange.




Good job young padawan. You know I "sniff out" all of the "broken case" threads

Yessssss masterrrrr haha

 

[Quingquad]

It's exactly as yamaha28 said, generally excessive piston to cylinder clearance from running an engine ragged (long past when it needed freshening up) letting the piston slap around inside there and breaking the skirt off. It falls (as gravity would have it) down into the bottom end and gets caught between the crankshaft and crankcase. Not all that uncommon an occurance unfortunately... and generally preventable with proper maintenance.

This blaster had very good compression before I split the cases. Can that be used to presume the piston to cyclinder clearance was ok? The piston and crank also appeared in good shape during dissasembly... Could the balancing gear be at fault?

 

[sicivicdude]

This blaster had very good compression before I split the cases. Can that be used to presume the piston to cyclinder clearance was ok? The piston and crank also appeared in good shape during dissasembly... Could the balancing gear be at fault?

Generally not the balancer gear as it cannot pass into the center case halves.

You can measure the cylinder to piston clearance once everything is ready to go again.

It could also have been FOD (not related to the piston at all) but you'd generally see damage to the combustion chamber and crankshaft it that were the case...

 

[sicivicdude]

I've had a set of cases like that before. sicivicdude does a great job repairing them.

Here's a before and after.

You did a good job with those pics man. I have a really good camera but always seem to forget to take pictures of the work I'm doing/got done.

 

[best]

This blaster had very good compression before I split the cases. Can that be used to presume the piston to cyclinder clearance was ok? The piston and crank also appeared in good shape during dissasembly... Could the balancing gear be at fault?

No, my guess would be that it swallowed a piston skirt, and then was repaired.
Piston chunk removed, new piston and hone job, disgruntled owner at poor starting and high oil consumption, sold cheap.

Get the case patched up and you will have a buy!