Freshly assembled XJ550 motor blows up, help w/post mortem

Re: Freshly assembled XJ550 motor blows up, help w/post mort

You sly salesman you! haha.

 

Re: Freshly assembled XJ550 motor blows up, help w/post mort

The other thing I was thinking it would be good to look at, once the motor's torn back down, was the wristpin of the seized piston. If the wristpin was binding or frozen, that would add a lock of rocking action to the piston and could certainly account for causing the seizure.

 

I wonder if the shrapnel was a wristpin circlip?

(BUMP) So did you find out anything more?

 

Re: Freshly assembled XJ550 motor blows up, help w/post mort

I,m with bigfitz on this.I reckon that , judging by the position of the cylinder wall damage,that a circlip has let go.Either not propery seated,or fatigued(recommended not to be re-used) and worn to the point that it could work its way past the piston.Wonder what,s sitting in the sump.

 

Re: Freshly assembled XJ550 motor blows up, help w/post mort

G,day again. Just had a closer look at the pictures again.It would appear that not only has the sleeve moved down, but that the sleeve has actually been torn away from the top retaining lip.Can you imagine the amount of force that would have to be applied to do this?The piston would have to be jammed incredibly solidly,very suddenly to do this.There is no way in the world that ring spacing ,or oil problems could have done this.If oil were a problem,it would have probably shot out the bearings first,not this. It seems to me that anything coming in from the top would have caused more irregular bore scoring, not the regular pattern seen here,anything big,like a nut left in there,would have probably holed the piston before jamming it,and stopped it turning over anyway.given the small amount of clearance at TDC. I can only imagine what the damage below is(iceberg principle), bent crankshaft,conrod,etc. It may be easier to start over ,It,s a real $hit.

Hope you find a solution,best wishes, Murray

 

HCP10307 Aftermarket BOROSCOPE with 18" long non-obedient shaft and with obediant shaft attachment......giving you the best of both worlds. This unit also comes with a replacement light bulb, a mirror attachment on the end of the shaft (to provide 90-degree viewing abilities), and a magnetic tip for parts-retrieval tasks.
$ 229.95[/quote]

DAM I just payed $300 for one of those last week. It was led though, and has "MAC" painted on it. Works awsome for checking cylinder walls, tops of pistons, and valves. Tried checking out the girlfriends undies that didn't work to well :lol:

 

Wrong tool. Flowers usually work much better for this job.

 

Re: Freshly assembled XJ550 motor blows up, help w/post mort

Hate me if you will, but it look like metal fatigue caused the cylinder liner to separate from the upper rim, with disastrous results. I doubt that there is anywhere near enough power inside a ~135cc cylinder to create enough energy to pull the cylinder free from the lip. Looks like the liner failed and caused the damage, not the other way around. Once the lip is off, there is nothing preventing the liner from following the piston up and down if its hot enough. You can sweat out liners in an oven at ~300F-350F, if you invert inside the stove, they will fall right out. It was a junkyard engine after all, who knows what happened to it during its slumber. I've also seen a lot of circlip damage inside cylinders, and it takes the form of a set of vertical grooves along the side of the cylinder, not a catastrophic blow-up like in the photo, especially with so little running. It would also have taken a huge chunk out of the top ring land and piston crown if it had made its way up to the combustion chamber. My 2 cents.

I'd give it a good looking at before I started throwing accusations around.