562xp Big End Bearing Seizure

[Crocky28]

Ok guys. Thoughts on this one please. I’ve just had a 562xp come back in after seizing. First thoughts were something jammed as it was stuck solid. Pulled the jug to find that the big end bearing was seized, it’s had some serious heat through it. Signs of detonation on the piston. Light scoring on the exhaust side but nothing major and the jugs ok. This happened after the fuel was swapped from two stroke mix to aspen. A tank of aspen through it then it seized.

The saw is a 2021 which hadn’t seen much work before I ported it. I’ve ported a few of these now all with the same numbers, same machining etc. This one is the first with issues. Has the aspen killed it?

 

[Timjus]

maybe its aspen fuel cleaning carbon build ups loose and it hammered in top of piston

 

[Duce]

Looks like, maybe missing parts of that bearing and went through saw. Can only make out one needle bearing. What side of piston is scored, if any?

 

[cus_deluxe]

IMO, that damage to piston looks like debris damage. Pic of cylinder?

 

[cus_deluxe]

Did u p/v test prior to teardown?

 

[Duane(Pa)]

I’m no expert, but that looks dry AF... Was there any oil in the Aspen?

 

[LouCi4er]

Maybe he messed things up and got the aspen 4 instead of aspen 2?Internal of the saw indeed look dry.

 

[Crocky28]

Yeah the aspen I took out had oil in it. I thought it looked dry inside too.

I’ll get a couple of pics of the cylinder today. It looks pretty clean inside. There was light scoring on the exhaust side of the piston. Nothing like what you would see if it had been straight fuelled.


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[Crocky28]

Pressure and vac tested before tear down, no leaks.


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[huskyboy]

Pics of the chain…

 

[Crocky28]

Pics of the chain…

I’ll get some. What you thinking? I had wondered if it had jumped the sprocket and jammed up but it doesn’t look like it.


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[huskyboy]

I’ll get some. What you thinking? I had wondered if it had jumped the sprocket and jammed up but it doesn’t look like it.


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Might be a case of the ham hands and dull chain. Lol

 

[Duce]

Scoring on exhaust side, air leak. Scoring may be light because auto-tune was trying to compensate. Straight gassed usually gets both sides.

 

[Crocky28]

Scoring on exhaust side, air leak. Straight gassed usually gets both sides.

There’s only light scoring and it has no leaks whatsoever. Pressure and vac tested. I wondered if the auto tune didn’t adjust properly after the change to aspen.


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[Crocky28]

Maybe he messed things up and got the aspen 4 instead of aspen 2?Internal of the saw indeed look dry.

Just checked with the company. They don’t use aspen 4. Only 2.


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[Duce]

Dry bottom end, not enough oil if no air leak? Aspen 2 is 50:1 in your ported saw. Did you put the fuel in saw or did they use wrong fuel?

 

[Crocky28]

They fuelled the saw. I use stihl hp ultra at 50/1 never had a problem. The same company has 2 other saws i’ve ported running aspen with no issues. They are 357s though so no auto tune.


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[Crocky28]

That was my first thought when he called, that it had the wrong fuel. But I have no way to tell as it had aspen in it when I got it. However the piston and cylinder don’t look like straight fuel.


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[kneedeepinsaws]

I’m no expert, but that looks dry AF... Was there any oil in the Aspen?

This

 

[Crocky28]

This

The aspen I took out the saw has oil in it. The company only uses aspen 2. There were two guys cutting that day both using the same fuel and the other saw is fine.


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