Frustrations Rebuilding a 440

[litefoot]

I posted on a different thread about my problems rebuilding a 440. I had debris still in the crank I had not totally cleaned out which scratched up a brand new OEM piston. I tore down the saw, cleaned out the crankcase (thoroughly, I thought), buffed out the piston scratches and all was fine until today. Tried to start the saw. Rope got stuck. Took off the muffler...more black debris. Here's pic of what was in the muffler. It's not carbon and no the nickel wasn't in there.

And a view looking down into the crank.

This saw had a toasted p&c when I acquired it. What do you think this is? Is there a bearing disintegrating down there. I see more flecks of the black stuff in the crank case. I removed about the same amount of debris the first time. Another question? How much lateral movement should that connecting rod have on the crankshaft bearing? Thanks everyone. I'm tired of tearing down this saw over and over....but realistically, I'm afraid I'm looking at maybe splitting the case to get to the bottom of this.

 

[04ultra]

Split crank case .......

 

[PES+]

It looks like it may be the piston pin bearing cage.

 

[blsnelling]

I recently had a 064 I rebuilt where the cage of one of the crank bearings was totally gone. Maybe yours is coming apart.

 

[Lakeside53]

Yes, the MAIN crank bearing cage.

Tear it all down.. new bearings...

Lateral movement - lots... but "rock" is less... and hard to describe...

 

[troutfisher]

I'd split the cases and see where it's coming from. Let me guess.....it was fed 50:1 mix?

 

[blsnelling]

How's your new P&C? I hope they survived.

 

[Erick]

Yep, pieces of the phenolic bearing cage on one or both of the crank bearings comming apart. Your gonna need to split the case and replace the bearings.


Or you could just sell that old worn out thing to me.

 

[litefoot]

Yes, the MAIN crank bearing cage.

Tear it all down.. new bearings...

Lateral movement - lots... but "rock" is less... and hard to describe...

Andy, is that the bearing you see in the pic (end of connecting rod) or one of the others (clutch/flywheel side)?

How's your new P&C? I hope they survived.

Brad, the piston is scratched up but repairable. The cylinder, somehow, came away relatively unscathed. That Nikasil must be tough stuff.

 

[Lakeside53]

The bearings on the outside ends of the crank... clutch and FW sides.

 

[blsnelling]

The 064 I found this one on showed no play at all in the bearing when I tore it down. It was smooth as well. I even pulled the seals and flushed the case. Unfortunately, you can only see the inner race on the flywheel side, so I didn't catch it. Upon first startup after the rebuild, I noticed a "rattle" on deceleration. I finally found that the flywheel was hitting the coil. What was happening is that the balls would all bunch up on one side and at that point, there was lots of lateral play in the crank. There were no signs of the cage when I flushed it, so it was long gone when I got the saw. Fortunately the owner ran it very little before I went through it.

 

[PES+]

LoL

A nibble.......but I didn't hook him.

:spam:


How bad was the piston beat up?

The non metallic cages usually are not catastrophic after the trip from the case to the muffler but it can get ugly with bad luck

 

[Martinm210]

My 044 case had a similar issue. I replaced the case/crank/bearings, but now considering buying fresh bearings anyhow. Crank bearings always seem to be a bit of a crapshoot if deciding to save them and just do the top end, especially if it's getting of age.

Both bearings area around $50 (30 for one and 20 for the other) from your stihl dealer. You can also buy a gasket set with the seals from Baileys for $10 plus shipping.

Here's Andy's very helpful thread on case splitting 101. I've printed it off and put it in my binder with the IPL and workshop manual. I'm about to go in myself..
http://www.arboristsite.com/showthread.php?t=40590&page=2&highlight=066

 

[Bowtie]

Yep, replace both bearings and dont worry anymore! That 044 is worth it. Good luck on your project! :greenchainsaw:

 

[litefoot]

Thanks for that link Martin. I think that's one of the prized links I save as well. This will be all new territory for me; splitting the case, that is. Now I've just got to find the time.

BTW, what would cause the bearings to fail that way? Particles from the upper end siezure? Overheating from the straight gas? This is a rather low-hour saw.

 

[litefoot]

A nibble.......but I didn't hook him.

:spam:


How bad was the piston beat up?

The non metallic cages usually are not catastrophic after the trip from the case to the muffler but it can get ugly with bad luck

Ahah! That 'splains things a bit. I put a magnet to the little black pieces and it didn't attract. I knew it wasn't magnesium, but I didn't know from whence there would be plastic down there.

 

[Jacob J.]

It would depend on what originally caused your top end to fail (before you got it). Usually when I see that, it's from running lean.

 

[Bowtie]

If it was overheated, the plastic cages can become brittle and break easily. I have seen that on saws, and run into it all the time on the photocells on kerosene and propane space heaters.

 

[Lakeside53]

I'd guess it's combination of heat and fuel additives. You can heat PA (nylon) all day, and it won't get brittle without something else acting on it.

 

[PES+]

Count your blessings

You would be far unhappier if it was a different brand with metal cages that let go.

I'm concerned about Andy though.....he didn't blow his top at my trolling