3120

[motosierra]

Anyone know what could cause a crankshaft-rod bearing to go?..thanks

 

[Lawn Masters]

other than heavy use? lack of lubrication for an extended period of time, or lack of cleaning the air filter, which would also show on the piston because the dirt would wear it down some too, and make the problem apparent.

 

[TimberPig]

Too many revs, inadequate lubrication, a lot of use, lemon bearing, dirt ingestion, are the main ones that come to mind.

 

[Grande Dog]

TimberPig hit it on the head. The only other things that come to mind is excessive carbon, (piston is hitting the cylinder at TDC) or pre-detonation (low octane fuel).

Grande Dog
Master Mechanic
Discount Arborist Equipment and Tree Care Supplies

 

[motosierra]

Thanks for all the knowlegable answers...it failed .without visible or discernable damage to the piston, cylinder, or crank bearings as far as I can tell.

 

[motosierra]

update...upon closer observation of the piston it seems that apparently something (of possible aluminum origin) made its way into the combustion chamber... a small indentation at edge of piston and a small deposit (tip of match size) of a material that appeared to be melted aluminum (embedded in piston) also close to top edge of piston .....corresponding to "side edge" of the exhaust port. Minor scratch at top of cylinder where piston with "object" would have made contact... and minor drag marks (scratching) length of stroke on cylinder below "side edge" ... I hope this description is comprehendible....

 

[shtoink]

Comprehendable, but not pretty...

That sounds like it sucks very much bad, sorry to hear it.

 

[TimberPig]

The damage you describe could also have been made by a piece of the crank bearing as it disintegrated and passed through the transfers, got pinched between the piston and head and then went out the exhaust port.

 

[OR_Native]

I was milling away with my brand new 3120 (like 3 total hours on it) and it just stopped dead. I took it in to the dealer, and had them take a look at it. They determined that it was caused by bad crank bearings. They contacted Husqvarna for warranty repair authorization and go it. The Husqvarna rep admitted to them that Husqvarna had received a bad batch of bearings from their bearing supplier. The rep said that the saw would have been recalled eventually. Husqvarna would not honor my request for a brand new saw. I don't know how old your saw is, but if it is newer, I'd think this would be worth looking into.

 

[Lawn Masters]

I'd say if they got a batch of bad bearings, a recall should be made ASAP to prevent failures from occurring in the first place.

 

[Simonizer]

I have seen electrodes from spark plugs come apart and lodge themselves in piston crowns. Sometimes a piece of the bearing retainer, small or big end. This is a very timely post that underscores my comments in the "Stihl 880 or Husky 3120" thread. I have seen this before with the biggest Husky.