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

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

Really? This seems hard for me to believe as the old motor had 60k plus miles on it, and I inspected the two motors side by side. The original 60k plus mile motor was in visibly worse condition on virtually all the wearable surfaces, such as the HY-VO chain, bearings, pistons, gearbox, cam chain guides and tensioners, etc.

Btw, which pictures were you able to access?

 

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

My money is on seized, pulled liner down then ring escaped gap at the top.

Cylinders SHOULD not be tapered. They are round when new. The top will wear faster because the pressure causes the rings to bite the cylinder wall harder there.

 

You should measure the ring end gap at the top, middle and bottom of the bore in the ring travel area (this will give you an indication if the bore is worn or "ovaled"). Insert the ring in the bore, then push the piston in to "square" the ring on the bore.

The bore shouldn't be tapered through the ring travel area.

 

Good point, but a used bore WILL be tapered and the motor was built from used parts.
I guess we will see the damage soon, like tomorrow ????

 

On the topic of looking at the head, piston crown etc... any tools out there to look INSIDE without dismantling, via plug hole?

Like a camera on a stick?

I think I could make something like that...

 

Maybe if you're friendly with your local doctor you could take your bike down to him and he can perform an endoscopy..... :lol:

 

HOPEFULLY ON THE BIKE!

lol...

 

They actually make those.............

it46) Aftermarket hi-resolution viewing BOROSCOPE. These amazing devices use a miniature hi-resolution (7200 pixels) camera mounted on the end of a 1/4" diameter flexible (non-obedient) or a 3/8" diameter fixed (obedient) shaft and which allows you to probe all the dark, hidden recesses of things and then display what's "in there" on a full-color screen. Want to see what condition your cylinder walls are in, without pulling the head?: then go in with the magic wand thru the spark plug hole and get a lighted, detailed view. Condition of your primary chain guide? The deep dark recesses of your fuel tank? Just like superglue, these have a 101 uses.....probably more.

A pressure-sensitive, momentary-on, housing-mounted light switch allows you to illuminate objects with a powerful halogen lamp and explore items within 3/4" of an inch away, and within a 40-degree field of view, while an integrated focus ring allows for smooth, continuous focuing precision.

HCP10306 Aftermarket BOROSCOPE with 18" long non-obedient shaft.
$ 154.95

HCP10305 Aftermarket BOROSCOPE with 18" long obedient shaft.
$ 154.95

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

 

Little pricy, think I'll stick with hacking my old PC camera up and a real strong light We'll see.

I knew you had em too

If you think about it, it's really not that bad a price. Just don't have the money to blow on something like that

 

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

It's an INVESTMENT, Doug, not an expense.

BTW, you should think of all the products that I offer in that manner.......

 

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.