Look what I found.

[mlrblaster]

I found a blaster on craigslist the weekend before Thanksgiving. The guy said that it would start with some good fuel. I was only interested in it because it had new tires with aftermarket rims on the front, decent tires on the back, DG aluminum front bumber, new aftermarket coil, Works Performance front shocks, and he was asking $600. After getting there and looking it over and giving it a few kicks I realized that the reason he was unable to get it started was that it had no compression. I ended up paying $420 because itprobably just needed a top end rebuild. I pulled off the head off the weekend of Thanksgiving and you could wiggle the piston back and forth in the cylinder. I figured at that point that it was just run until the rings were completely shot. I pulled the cylinder off today to inspect the cylinder and piston. This is what I found.

I am wondering where that piece of missing ring went. Im sure some of y'all have seen this before. I measured the piston and if I measured correctly it was 66.5 mm. From what I have read on here by many differrent people, I believe that whoever did the bore job did not chamfer the cylinder ports and the top ring caught the exhaust port. All the ports feel quite sharp. I'm not sure if that would be caused from normal wear or not being chamfered. I thought this might be helpful for others to see what happens if my assesment is correct.
Anyone have any ideas of the cause if I'm guessing wrong?

 

[Blaaster]

As the lower ring is intact, the chances are that it was spat out through the exhaust port.

You are possibly correct the ring snagged a port due to no chamfers.

 

[Davo]

This is the exact scenario I was dealing with this summer on a craigslist find. Same look to the piston. My rings shot out the exhaust port. (But don't take my word for it). I know cause the pieces fell out of the expansion pipe and I could account for what was missing. I made sure the machine shop chamfered the ports when they bored a replacement jug. Nice find with some of the mod parts.

 

[Awk08]

I'd be splitting those cases for a thorough inspection "at the least"
with that much damage and amount of material missing, I wouldn't chance everything went out the exhaust and not down into the bottom end to contaminate the crank and rod bearings.

 

[dirtysquared]

I'm with Awk on this one too. To go to all the trouble of getting the top end redone, just to kill it quickly because of something floating around in the crankcase would suck.

Splitting the cases ,cleaning and inspecting everything is necessary here, if for nothing else, just to clear any doubt about the bottom end

 

[Blaaster]

Yup sure thing, split the cases as it is possible that some material has migrated into the bottom end!

Tell tale signs that something has got past the lower ring!

 

[mlrblaster]

I am in agreement about splitting the cases. My plan was to rob all the aftermarket parts then get it running (as cheap as possible) for a quick flip to get my money back out of it. With the state of the top end and what is needed to make sure it is right am I going to end up with more in it than I could get back out of it? I can't put this back together and not do it right, I could not do that to someone. I've unfortunately had that done to me in the past. The chasis has been spray painted black and a terrible job at that. The ones I've bought to flip have all brought around $650-$750. Is this going to be worth what I'll have in it?

 

[Bluesman]

Swap out all the parts you want with stock parts and put it out there for $400 OBO. I bet someone would give $300 for it and build it themselves.

Or save the motor and CDI, and part out the rest.

 

[Davo]

Yep that's why I take my time and rebuild with care. I stand behind what I get rid of. "Tight" says a lot about the care of it. I was lucky with my yellow one. Someone took good care of it. My carcass' were another story. It made me grumpier every sign I found of mis care. I laughed driving away from one dude, "yer YFZ will be in the same shoes as yer Blaster in 6 months"