Husky 394XP New Project

[rupedoggy]

Explain to me how, in your mind, a little missed aluminum transfer could cause that meltdown.

 

[WolfMann]

Friction from ring traveling over it at 10,000 plus rpm causing excessive heat? Eventually creating a hot spot and causing the ring and piston to seize? I'm shooting in the dark here, I did think the cylinder looked spotless, would trace amounts of transfer not be an issue?

 

[WolfMann]

Missed transfer was the only thing I could think of, the crank seals tested good under pressure/vacuum I believe that would've also revealed any defects in cylinder/intake block. I had the pressure plate mounted to intake block while testing. There was no carbon buildup in exhaust port. Feeling pretty stumped here.

 

[Gord404]

Had and rebuilt a few of them, quite a solid saw and tons of power. Guess I like them also it seems they didn't cut any corners on quality and easy to work on -I use a Meteor piston and rings, seems great quality and a good price IMO, one on the go now and buying a couple of parts saws most likely today for rebuilds or spares, worth the effort.

 

[JimM]

Missed transfer was the only thing I could think of, the crank seals tested good under pressure/vacuum I believe that would've also revealed any defects in cylinder/intake block. I had the pressure plate mounted to intake block while testing. There was no carbon buildup in exhaust port. Feeling pretty stumped here.

I would hazard a guess that your factory carb setting was actually too lean.

 

[WolfMann]

Thanks guys, I mentioned this was a barn find, but I'm finding the con to that is not knowing the saws history. Someone mentioned earlier to check for cracks on intake block. I didn't see any at the time (and still don't) But is it likely, or possible, that there's a crack on intake block or in cylinder, something that opens when hot and causes lean mix? Has anyone heard of that happening, more so with cylinder?

 

[WolfMann]

Can I get some opinions on this cleanup job guys?

 

[WolfMann]

Went over it a few more times.

 

[WolfMann]

Last one, what makes me nervous is when I look very closely I can see a few discolored specks. Is that transfer? Will it cause another failure with new piston. I don't mean to sound neurotic, I just want to make sure it's ok.

 

[JimM]

You will be doing it again. Good practice though.

 

[spyder62]

Nice thread. Hope you get everything worked out

 

[spyder62]

How do the bearings look.

 

[WolfMann]

Thanks spyder, bearings looked ok and didn't have any play to them but I'm starting to think I should replace them just to be safe. Didn't split crankcase the first time, probably a good idea to do it now.

 

[WolfMann]

JimM I'm not sure I understand, are you saying those specks will cause another failure? I'm not done cleaning it but I think part of the problem is my not understanding how trace amounts of transfer would impact piston. Does it melt into groove causing seizure of rings? Sounds like I want to take everything to a consistent shine yeah?

 

[Gord404]

had a rebuild fail a while back, clutch side bearing was gone, felt good when I put the new seals in, bits of cage took out the piston, another lesson learned in my learning curve.

 

[WolfMann]

Thank you Gord, I'm looking at it the same way, this is the first saw I've really gotten into and it has been a steep learning curve. But I know a lot more now than I did a couple weeks ago. And I intend to keep getting better at it.

 

[WolfMann]

And I believe JimM was right about the factory settings being too lean, the one time I pointed a tach at it, it showed idle at 3200 and fast idle just south of 13000. A fair step above the workshop manual recommended 2500, 12500. I think at that point I missed the "trees for the forest" I figured it was running and set to factory so it must be fine. I also spent time running it at half throttle, which I now understand can cause an additional lean state. I should've compensated more for larger filter, and while crank seals tested good during assembly, it would've been wise to test again after running it some.

 

[spyder62]

I put a oem 346 pc on a 350 a few months back. Put it all back together but didn’t start it because it rained. I had posted pictures of everything as I was doing it. Someone posted that one of the bearing cages looked bad. I pulled it apart and sure enough it was toast. Glad I pulled it apart. And glad for the knowledgeable people on here that zoom in and know what they’re looking at.

 

[srcarr52]

Missed transfer was the only thing I could think of, the crank seals tested good under pressure/vacuum I believe that would've also revealed any defects in cylinder/intake block. I had the pressure plate mounted to intake block while testing. There was no carbon buildup in exhaust port. Feeling pretty stumped here.

Did you replace the fuel filter and fuel line?

 

[WolfMann]

I did replace fuel line, fuel filter looked almost new, so I left it alone.