What caused this 064 to blow up?

[Yotaismygame]

First off, I have never seen a shielded bearing in a saw before. Then the case half blew from the inside out. Something got in the case? Doesn't surprise me if this is the reason, because the guy I got it from I also got a 372 from and that saw had some weird stuff going on with it too. He was a real brainiac....

Nothing obviously wrong with it except that hole

 

[atpchas]

A bit of JB and you'll be good to go...

Seriously, I had a saw where the con rod snapped and the part of the rod still connected to the crank punched a big hole in the bottom of the case.

 

[Yotaismygame]

A bit of JB and you'll be good to go...

Seriously, I had a saw where the con rod snapped and the part of the rod still connected to the crank punched a big hole in the bottom of the case.

Ive seen some gnarly carnage before. Really i'm interested in the shielded bearings.

 

[drf255]

Shielded bearings pretty common in older Stihls. I’ve seen it many times on 036/044/064.

That case is weldable.

 

[L34]

So are there parts missing/damaged elsewhere.

 

[Yotaismygame]

Shielded bearings pretty common in older Stihls. I’ve seen it many times on 036/044/064.

That case is weldable.

That’s interesting. I’ve had plenty of old stihls and haven’t seen that.

 

[ML12]

Shielded bearings were on all large Pioneers and PM saws from the 1950s through to the 1970s. Not the greatest idea as they can lessen the lubrication that the crank seals see, I usually replace them with open caged versions.

 

[huskihl]

People say those shielded bearings won’t last in a saw, yet they survived for 30-40 years with countless cylinder rebuilds.
No idea what caused the hole. Something as small as a circlip or rod roller bearing would do it. Case bearings going bad could also cause it

 

[lone wolf]

Looks like a rod bearing went and allowed the rod to hit the bottom whether it be a side bearing or the rod itself OP which bearing is wrecked?

 

[Yotaismygame]

All bearings are in good shape. I'll have to double check the big end rod bearing to be completely sure.

 

[lone wolf]

All bearings are in good shape. I'll have to double check the big end rod bearing to be completely sure.

I suspect one of the bearings are bad and you aint seeing it. Look ,feel ,listen compare.

 

[Bob Hedgecutter]

I suspect one of the bearings are bad and you aint seeing it. Look ,feel ,listen compare.

Or- is it possible, a bearing failed, got in between the bottom of the rod and the case (or the rod dropped) enough to severely fracture the case half but NOT actually blow the chunk out- previous owner rebuilt the bearings, ran the saw and crank pressure blew the chunk out?
So bearings appear fine- but there is a bloody big hole in the case.

Not that I have ever seen this happen- but just thinking of a possible scenario that would show both of you to be correct.

 

[lone wolf]

Or- is it possible, a bearing failed, got in between the bottom of the rod and the case (or the rod dropped) enough to severely fracture the case half but NOT actually blow the chunk out- previous owner rebuilt the bearings, ran the saw and crank pressure blew the chunk out?
So bearings appear fine- but there is a bloody big hole in the case.

Not that I have ever seen this happen- but just thinking of a possible scenario that would show both of you to be correct.

IDK I highly suspect a bearing is bad and it just seems OK because it seized and now seems tight when cool but isnt good.

 

[lone wolf]

@pioneerguy600

 

[pioneerguy600]

That`s a big hole, air leak I say.

 

[Yotaismygame]

Hard to check the sealed bearings. Once I punch them out ill pull the covers off and have a look. No needle bearings missing. The cylinder was missing a bolt. I suspect the last owner had something to do with this. The 372 I got had been "rebuilt" but on the pto side seal seat there was a big chunk missing. Like someone had knocked it with a punch and hammer. Top end was toasted. I bought it for cheap but majority of the saw ended up being junk. Became a parts saw. I also got a 288 from him with a toasted AM top end. That ended up being a cracked case and was sucking in bar oil. Guarantee you he got the saw with a bad top end, replaced it expecting it to be good.

I'm rebuilding and porting this saw for myself.

 

[Yotaismygame]

There is a slight indent on the lip of the intake skirt. Maybe ingested something?

 

[siouxindian]

First off, I have never seen a shielded bearing in a saw before. Then the case half blew from the inside out. Something got in the case? Doesn't surprise me if this is the reason, because the guy I got it from I also got a 372 from and that saw had some weird stuff going on with it too. He was a real brainiac....

Nothing obviously wrong with it except that hole
View attachment 815866View attachment 815867

well for 1 thing 2 strokes dont have sealed bearings.

 

[Yotaismygame]

Post 4 and 6 said otherwise...

 

[Justsaws]

Mashed up piston parts getting swung under crank weights. Lots of manufacturers tossed sealed bearing in saws at one point in time. Some seemed to work better than others. The lower the rpm the better.