441cm piston stuck in cylinder (again) bearings destroyed

[imagineero]

Few months back I posted this thread about a piston stuck in cylinder

https://www.arboristsite.com/community/threads/441cm-piston-stuck-in-cylinder.317717/

It sat on the shelf for a while till I got to it last week and split the case to try to get at it a little better, where I discovered the flywheel side bearing had not so many bearings in it as it ought to. in light of the time that's lapsed and the new information I figured it would be better to start a new thread.



The missing bearings were not inside the crankcase, so it's a fair bet at least one of them got sucked into the jug. Surprisingly, the jug appears to be in good condition from what I can tell looking through the plug hole. what looks like scratches in the photos is just some shelf muck that's stuck to the oil.

So, the piston appears to slide all the way up to TDC (or at least very close), and slides down about 9/16" where it doesn't want to go any further. I haven't forced it in any way. If you're looking up to the cylinder from the bottom, the piston/crank can be rotated about 1/8 of a turn counterclockwise at TDC, and only a couple degrees clockwise. In the lower position it rotates almost a full quarter turn counter clockwise and again only a degree or two clockwise. It seems to follow the shape of the skirt/window a little as it's rotated, you can feel something.

This pic from below shows the intake port when it's as up as it's going to get. Again, the stuff on the cylinder walls is just dirt.



And this one shows how far down she comes from the exhaust port; lower piston ring comes into sight.



So.... I'm open to any ideas. I'm guessing a bearing or maybe part of a ring caught in the transfers. Could try maybe welding a zerk to a plug and grease gunning it out? Would be nice in fantasy land to imagine that I could salvage the whole lot, but if anything has to be damaged it would hopefully be the piston. Jugs are $$$ in australia (about $800 from memory) and pistons are only $. I could use the crank in another saw, or in the same saw. No idea what other damage is done, maybe piston slammed into top of jug, crank bearings probably shot, maybe crank too.

Open to you guys.

 

[BuckthornBonnie]

Dang... could be any of those ideas blocking travel, yep. Maybe try a few less aggressive methods before punch through the spark plug and decomp hole lol. Piston is sacrificial at this point. Meteors for this series are very good (Meteor piston, that is).

 

[Chainsaw Jim]

None of the bearings escaped. The plastic cage has broken up into little pieces and a chunk of it is stuck in one of the transfers.

 

[Brent Nowell]

Yikes but yes i have heard of plastic nylon bearing cages giving out making it appear that bearings are missing...
I like your idea with the grease use hydraulics to push it out. If that doesnt work a wooden dowel through the spark plug hole and a mallet to force the piston out, seems one of the rings is siezed and caught up. If your lucky a hone and replate might fix the damage to the cylinder after. I wish you luck my friend

 

[JimM]

Yikes but yes i have heard of plastic nylon bearing cages giving out making it appear that bearings are missing...
I like your idea with the grease use hydraulics to push it out. If that doesnt work a wooden dowel through the spark plug hole and a mallet to force the piston out, seems one of the rings is siezed and caught up. If your lucky a hone and replate might fix the damage to the cylinder after. I wish you luck my friend

Lol

 

[BangBang77]

None of the bearings escaped. The plastic cage has broken up into little pieces and a chunk of it is stuck in one of the transfers.

THIS +1

 

[BuckthornBonnie]

If you do break something, please post pics with no shame.

I’ve had a ms390 with stuck rings, a 361 with rope in the ports, and and 036 with locked bearings/crank. All are running now despite some ugliness getting them apart. Makes the normal lean seizures or bearing failures seem easy.

 

[imagineero]

That's about the best news I've had this week.... I think any advice how to fest go about it? Could I remove the decomp etc and put the jug in the oven and maybe melt the plastic?

 

[anymanusa]

How does something like this happen?

 

[L34]

Just fitted a Hyway P/C $190AU to my 441c.Seems OK at the moment but haven't cut much wood.
Seemed to have good ports and bevels to me.

 

[imagineero]

Just fitted a Hyway P/C $190AU to my 441c.Seems OK at the moment but haven't cut much wood.
Seemed to have good ports and bevels to me.

Some of the aftermarket pistons are not bad, especially with OEM rings. The cylinders just don't make the kind of power that OEM jugs do in my experience. Worst of the lot are the generic "big bore" unbranded Chinese stuff.

 

[imagineero]

How does something like this happen?

I try to limit myself to only one "why?" Question per day for my sanity, and this wasn't one of them. If you run a tree service you're gonna go through saws. They're more of a consumable item than an asset. A busy tree company might put more hours on a saw in 2 or 3 days than many home owners would in a year depending on the type of work they do. We average about 10 months for a climbing saw, a year for a smaller ground saw. Mid to large ground saws might get 2 years or 3 if you're lucky.

That was a particularly bad week for us, the boys had managed to put 4 saws out of service in unrelated incidents when this one got broken. Another 441 had the crank snap on the clutch side, second time I've seen that in about 6 years. 661 lean seized, repaired under warranty by Stihl, had one of the earlier faulty coils. Another saw had a broken Phil cord which is no big deal.

This particular 441 had been making a slightly weird "ting ting ting" sound at idle for a while. I took it apart and reassembled the week before but couldn't find anything... checked squish, looked at the flywheel and clutch, nothing obvious. In retrospect I guess the bearing was screwed and the loose bearings were sometimes in the right place and sometimes not. We don't ever have unmixed fuel in the truck so it wasn't that. Not ever seen it happen so I'm not too concerned. It had almost 2 years on it already so it'll just be a parts saw or whatever.

 

[blsnelling]

Yup. No bearings are missing.

I suspect that you have a circlip stuck in a transfer port. I'm not sure how you'll get it off.

 

[CR888]

Pouring a 1/4 cup of 2stroke oil down plug hole couldn't hurt anything. Looks tricky!

 

[imagineero]

Yup. No bearings are missing.

I suspect that you have a circlip stuck in a transfer port. I'm not sure how you'll get it off.

Where’s ant man when you need him?

 

[rupedoggy]

Not what you want to hear but a strong rod through the spark hole and the piston down as far as possible, beat that piston out.

 

[Thommo]

I would try twisting the cylinder as you lift it from the piston to see if it releases something. That ring looks strange through the exhaust port and could be broken and hanging up in a transfer port.

 

[CsClimbr]

I would try twisting the cylinder as you lift it from the piston to see if it releases something. That ring looks strange through the exhaust port and could be broken and hanging up in a transfer port.

I agree, something doesn’t look right with that top ring. If it was me and at all possible to get at that ring, I’d attempt to carefully drill the ring itself in a spot or two and maybe chunk it out to see if that would give things more room to free up. Just a thought, rings be cheap enough

 

[pioneerguy600]

A few things I would try first before beating the thing apart. First turn the saw upside down, turn the crank til the piston is in a loose position, tap on the cylinder head, a couple fast hard rapps, then try turning the crank around. If no results then turn the saw on its side, tap the head again, try to rotate, do both sides if necessary. I have had a lot of experiences on unlocking old vintage saws, many were just rust stuck but a few had broken rings stuck out in ports, one had a wrist pin out in a transfer, a few with foreign bits of bearing cage and big end needle bearings rolling around in the ports.

 

[imagineero]

A few things I would try first before beating the thing apart. First turn the saw upside down, turn the crank til the piston is in a loose position, tap on the cylinder head, a couple fast hard rapps, then try turning the crank around. If no results then turn the saw on its side, tap the head again, try to rotate, do both sides if necessary. I have had a lot of experiences on unlocking old vintage saws, many were just rust stuck but a few had broken rings stuck out in ports, one had a wrist pin out in a transfer, a few with foreign bits of bearing cage and big end needle bearings rolling around in the ports.

All good ideas and will give some a try. I may not have been clear enough in the description, I've already split the case halves so I just have the loose jug/piston/crank to deal with. In which case maybe put the jug in a vice and try working the crank a bit while rapping? There's no urgent hurry with this, so anything that's a possibility and unlikely to do further damage is worth a try.

Worst case is maybe try to drill the piston from below enough that I can get the crank out of it unharmed, which would give enough access to get a dremel/die grinder in there and just slowly work away at it and piece it out without damaging the jug if possible