What's on your bench?

[mdavlee]

One fin won't matter. I'd say it come loose at one time or something like that.

 

[Stihlsmoking]

Thanks. I'll probably have more questions once it's apart.

 

[VinceGU05]

I usually snap off the opposite fin to keep balance as close as possible.

 

[MustangMike]

Here are the pics: What do you guys think?

Would sure appreciate some comments on this. Thanks.

 

[TJ the Chainsaw Mechanic]

Finished the 192 and threw it out the door. Waiting on sprokets for a 460 and 260. Have the 391 torn apart still...everything bottom end and top end looks find(make things harder)....and a Honda 4 stroke weed eater I need to get parts coming for.

 

[Stump Shot]

Would sure appreciate some comments on this. Thanks.

If it were on my bench I would not cut that off and call it good. I would take the time to pull it re-cement it in place so it does not leak. I would then take a centering punch and "stake it in" inside and out, insuring a non-repeat occurrence. No sense in doing a repair job, only to have the same thing happen all over again. Also cutting it off would jeopardize the crank bearings with filings.

 

[VinceGU05]

Would sure appreciate some comments on this. Thanks.

Put the piston back on and see if it goes far enough down to hit it.

I did think of this too.

P.S take closer pics. They are way too far back to see details/tell tales [emoji6]

 

[mdavlee]

Would sure appreciate some comments on this. Thanks.

If it's hitting the impulse nipple I'd see if you could pull it out and install a shorter one. Being soft the shavings shouldn't hurt the bearings but I'd not want to wonder on someone else's saw.

 

[MustangMike]

There is a stop on the nipple to prevent it from going in further, I'm wondering if they all stick through like this, or if the wrong one was installed? Was hoping someone else had encountered something like this before.

The intake side of the piston is longer than the exhaust side, the break is exactly in line with the nipple. Perhaps it only contacted it if the piston got hod or sloppy? I don't see any mark on the nipple, but also can't find any other evidence of what caused the break.

I think the mild piston scoring (not evident on the cylinder, but I will clean it anyway) occurred after the "event" and the locking of the top ring. They still ran this saw after this happened, but complained it had no power! That locked top ring would tilt the piston a bit and cause the scoring (IMO).

The case has to be flushed any way, especially since it still had piston fragments in there. I'm thinking of temporarily removing that saddle, cut off the excess nipple, then run a drill bit through to ensure it is still open.

 

[mdavlee]

Put a shop vac right beside the case as you're filing it down and lay the saw on the tank handle if you can to try to keep more stuff out of the crank bearings.

 

[MustangMike]

Put a shop vac right beside the case as you're filing it down and lay the saw on the tank handle if you can to try to keep more stuff out of the crank bearings.

Great suggestion, thanks.

If I do decide to replace it, do I need to heat the case? What is the procedure? I think Jeremy showed it once, but danged if I can find it.

 

[mdavlee]

I don't remember how the best way to install is.

 

[paragonbuilder]

I can't imagine a brass nipple took a chunk out of the piston without at least tweaking the nipple...


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[MustangMike]

I wish I could see evidence of contact also, but no. However, that nipple is perfectly lined up with the break, I just re checked it, wish I could get a pic, but it would not come out.

High speed & high temps can make strange things happen, and I can not find any other culprit.

I don't understand why the nipple would be designed to protrude through the case (instead of being flush with it).

 

[mdavlee]

With the cylinder on I don't see how it could rock that far to hit it.

 

[MustangMike]

Just putting the loose piston there, and aligning it with the rod hole, I can tell you it is very close. Tough to tell with the piece missing, maybe I should check it with the new piston. Still, I see no harm is removing a bit of that nipple.

It is very tight width wise & height wise, don't know why they would make it so close. Perhaps heat expansion enabled it to contact?

 

[Mastermind]

Mike......my eyes ain't good enough to see them pictures my friend.

 

[Mastermind]

On my bench.......

 

[Stump Shot]

On my bench.......

View attachment 33709

You been making a top secret 5 cylinder saw rig you haven't been telling us about?

 

[Mastermind]

You been making a top secret 5 cylinder saw rig you haven't been telling us about?

Well.........

I can't say.