She blowed up :(

[jbuckster07]

Drive almost 2 hours to ride today at Powerline Park in St Clairsville, Ohio. Got the blaster out, started her up, warmed up for a couple min or so. Made a couple runs up and down to she how the ride was. Pulled the clutch in shifted up and then crack and it stalled. Thought I just missed the gear and let the clutch out to fast or something. Tried to kick it over and was seized up.... FML. Here is the carnage. The piston skirt actually broke off!!! Just did a compression test last week along with a leak down and both were good. Had 130 psi and no leaks. Any ideas what might have happened??

 

[hudack]

Any play in thw rod

 

[89blaster89]

I know how you feel, mine blew up also, we drove 6 hours to ride, first ride out it blew, yours looks way worse though

 

[jbuckster07]

Any play in thw rod

A little bit, not enough to make it do that I would think. Plus is it possible that those chucks could have caused the little play in it? Idk lol. The walls dnt look bad I dnt think, let me get a pic of them real quick..

 

[jbuckster07]

Here are some picks of the walls. It's dark out best I could do.

 

[Awk08]

Busted cast piston skirts are usually due to 2 things....
not warmed up enuf or excessive piston to cylinder clearence.

 

[Blaaster]

By the look of the wear markings below the intake ports I would bet that a sloppy piston was at fault.

 

[hudack]

Measure the cylinder Il bet its out of spec

 

[jbuckster07]

Ok I will def measure the cylinder. The piston is a wsm and is .5 over bore. When I had it resized prolly 3 years ago I have them the cylinder and the piston so there wouldn't be any way there was a wrong sizing. He did day that he didn't have to bore it, just a hone since it was only .5 over. Will keep you guys updated. Though thanks for all the info!

 

[JBRoc01blaster]

What was the reason for the new piston and hone job when you last had it done ? I would also think too much piston to cylinder clearance was most likely at fault here. Do yourself a favor and have your cylinder bored and honed this time or face another rebuild in the near future ! ALSO if you have the means, go ahead and replace the bottom end while your at it, when a skirt breaks/shatters like that the amount of shratnel makes it near impossible to just clean out the crank/bearings etc.

 

[jbuckster07]

When I bought it, the guys I bought it from told me he just put in a new piston a rings. Decided not to trust him so I just went .5 over to know that it was done ok. I am def going to split the cases because I can she pieces of metal all over the bottom end. Now I dnt want to go all out and buy the big bore kit. Just can't afford that while trying to pay for a wedding at the same time. Since its .5 over what should I go up to next? There are only 2 more sizes right? .75 and 1mm over? Let me know what should be the best option. Next question, is the cast piston ok or should I but a forged?

 

[Herpderplol]

there are 8 total.

Stock is 66mm

Max is 68mm

.25 is one over, .5 is two over.

You might be able to do .75? Have it measured by a shop, dont trust your own measurements, you probably dont have the tool to check for oval in the center

 

[Blaaster]

As to cast versus forged piston, the choice is yours, they will both serve you well if you heed their needs.