Stihl ms194t piston problem

[Fil01]

good afternoon everyone
Today I ran into two blown stihl ms 194.
After disassembling both saw I noticed the same scoring on the pistons but the cylinder are mint.
There is just a few carbon deposit on the exhaust side but not enough to fall into the cylinder.
The groove on the piston is pretty deep
What do you think?
Ps one of the crank has a lot of play in the bottom bearing and both saws are packed with sawdust so they have probably overheated

 

[link]

I have heard "caber" rings all over the place, but if you are a prefect you could search for Meteor pistons as well.
Shouldn't be far from where you're at.

 

[link]

That is a profoundly practical saw you have there.

 

[Fil01]

I have heard "caber" rings all over the place, but if you are a prefect you could search for Meteor pistons as well.
Shouldn't be far from where you're

I’ll probably go oem since it’s not that expensive.
By the way my question wasn’t about buying the piston but why they failed the exact same way

 

[link]

I’ll probably go oem since it’s not that expensive.
By the way my question wasn’t about buying the piston but why they failed the exact same way

It should not happen, but if you go 40 to 1 (2,5% oil) at the fuel /oil, that would probably not have happened.

 

[SteveSr]

good afternoon everyone
Today I ran into two blown stihl ms 194.
After disassembling both saw I noticed the same scoring on the pistons but the cylinder are mint.
There is just a few carbon deposit on the exhaust side but not enough to fall into the cylinder.
The groove on the piston is pretty deep
What do you think?
Ps one of the crank has a lot of play in the bottom bearing and both saws are packed with sawdust so they have probably overheated

That type of damage is caused by a foreign object like a bearing that is disintegrating. You have some more detective work to do before even thinking about replacing the pistons. You also need to take a MUCH closer look at the cylinders as they are likely trashed as well.

 

[Fil01]

That type of damage is caused by a foreign object like a bearing that is disintegrating. You have some more detective work to do before even thinking about replacing the pistons. You also need to take a MUCH closer look at the cylinders as they are likely trashed as well.

Bearings are mint
And the cylinder still has the cross hatch from factory. The only thing I can imagine got in the way could be carbon

 

[cookies]

Bearings are mint
And the cylinder still has the cross hatch from factory. The only thing I can imagine got in the way could be carbon

if its mint then it shouldent be a issue to tear it down to the crank to inspect the bearings and stick new seals in. If that much metal went through my saw engine it would get torn down just to clean the metal fragments out of the crankcase ,bearings and seal lips.

 

[Fil01]

if its mint then it shouldent be a issue to tear it down to the crank to inspect the bearings and stick new seals in. If that much metal went through my saw engine it would get torn down just to clean the metal fragments out of the crankcase ,bearings and seal lips.

It is already tore down. These are clamshell engines and you can’t access the piston if you don’t take out the crank

 

[Oletrapper]

Bearings are mint
And the cylinder still has the cross hatch from factory. The only thing I can imagine got in the way could be carbon

In your opening thread you say one of the cranks has a lot of play in the bottom bearing. Is it the crank bearing or the rod bearing? Here you say the bearings are mint?
Your probably correct in assuming that they overheated. That would conclude that IF both saws were owned by the same person and gassed from the same tank, they may have been using the wrong oil and gas mixture. Carbs adjusted too lean possibly. Clogged with sawdust won't create a lean/hot condition but rather a rich condition from lack of proper air mix and excess fuel. Keep us posted on the rebuild. OT

 

[Fil01]

In your opening thread you say one of the cranks has a lot of play in the bottom bearing. Is it the crank bearing or the rod bearing? Here you say the bearings are mint?
Your probably correct in assuming that they overheated. That would conclude that IF both saws were owned by the same person and gassed from the same tank, they may have been using the wrong oil and gas mixture. Carbs adjusted too lean possibly. Clogged with sawdust won't create a lean/hot condition but rather a rich condition from lack of proper air mix and excess fuel. Keep us posted on the rebuild. OT

You’re right I wasn’t clear enough. Sorry
The crank bearings are good, one of the rod bearing is shot.
Yes both of the saws were owned by the same company and weren’t maintained correctly In my opinion.
Anyway I ordered piston and seals (75€ total)
I’ll update the post when I rebuild the saw

 

[SteveSr]

You’re right I wasn’t clear enough. Sorry
The crank bearings are good, one of the rod bearing is shot.

Which rod bearing? Big end or little end?

The remnants of the foreign object may still be in the muffler, especially if it still has the spark screen. You may want to have a look. Also anything left in the muffler could get sucked back into the engine causing damage to the new parts.

Can you take some good photos of the exhaust port side of the cylinder? There may be damage at the top or bottom of the exhaust port that may have bulged the aluminum into the cylinder and will catch a new ring.

 

[Oletrapper]

Which rod bearing? Big end or little end?

The remnants of the foreign object may still be in the muffler, especially if it still has the spark screen. You may want to have a look. Also anything left in the muffler could get sucked back into the engine causing damage to the new parts.

Can you take some good photos of the exhaust port side of the cylinder? There may be damage at the top or bottom of the exhaust port that may have bulged the aluminum into the cylinder and will catch a new ring.

 

[bwalker]

In your opening thread you say one of the cranks has a lot of play in the bottom bearing. Is it the crank bearing or the rod bearing? Here you say the bearings are mint?
Your probably correct in assuming that they overheated. That would conclude that IF both saws were owned by the same person and gassed from the same tank, they may have been using the wrong oil and gas mixture. Carbs adjusted too lean possibly. Clogged with sawdust won't create a lean/hot condition but rather a rich condition from lack of proper air mix and excess fuel. Keep us posted on the rebuild. OT

The damage shown doesn't indicate running lean or hot. And oil ratio won't cause that either.
It's damage from something like a ring locating pin or a bearing coming unglued.

 

[cookies]

Or the person worked on both saws sticking something incorrect into the cylinder to lock the engine, chipped the piston or left fragments inside the engine then proceeded to run it.

 

[huskihl]

Or the person worked on both saws sticking something incorrect into the cylinder to lock the engine, chipped the piston or left fragments inside the engine then proceeded to run it.

This is the only thing that makes sense to me to have the same exact damage in the same spot.

The only way they both could even do that and score the pistons in the same spot is if they shoved it through the spark plug hole