Stihl MS361 blown engine... what do you think of an aftermarket one?

[2-StrokeDude]

Hey all I'm new to the fourm, and I just had a friend give me 2 free Stihl chainsaws he had sitting in a barn for years. One of them is an old 041 Av Electronic Quickstop and the other is a newer MS361.

I'm currently working on the 041AV since it is the only saw with a good engine that isn't seized up but the flywheel exploded on it so I'm waiting for some parts to come for that. So while I wait I'm starting work on the 361 and upon inspection the engine is totally locked up. In fact it is garbage. Had a hard seize, piston fused to the cylinder wall and the part of the piston where the wrist pin goes through snapped. Not exactly what I wanted to find out as I was hoping to just throw in a $45 cylinder and piston and hope the bottom end was good, but that's not the case.

I am considering purchasing this aftermarket Farmertec engine on Amazon for about $140:

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Not exactly what I want to throw in there since it is made in china and I'd like a good solid original Stihl saw for personal use but it seems an OEM engine is not available, nor an economical choice. That being said, has anyone had good experiences with this Farmertec engine or their engines? Any bad experiences? Do you think this is a good deal on an engine like this?

 

[Bob Hedgecutter]

Well, I can say I have never personally had an engine seize that well- but I guess- possible.
You say the piston is basically fused to the cylinder? The wrist pin socket on the piston is broken?
So what exactly is wrong with the bottom end?

Had the bearings in the bottom end failed- entirely possible by the sounds as it has been run real lean and real hot- part of the bearing cage did a loop through the transfers and lodged between piston and cylinder- well yes that will stop and lock things pretty damn fast- with ugly results usually.

Clicked your link and it might appear the item you are suggesting is out of stock? You may be able to order the parts direct yourself and save somebodys mark ups.

The Farmertec stuff is cheap- you get what you pay for. It can make a saw run that was not running before- but usually at a lesser power rate and lower longevity or service life- well any experience I have had with them this seems to be the case.
Sometimes the Farmertec stuff fails within the first couple of tanks burned- sometimes it doesnt. But quality varies a whole lot between suppliers to them and batch to batch. I have seen new cylinders from them with missing plating- really ugly porting with no chamfer, but I have also seen cylinders from them that are pretty reasonable.

At the moment on their website- the Farmertec MS361 complete saw kit is only $153:69 plus freight- all the parts you need will be in there as it is a whole saw kit in parts- you just assemble.

 

[2-StrokeDude]

First off, thanks for the response and advice! And upon farther inspection the piston is not fused to the cylinder wall, there was a chunk of piston wedged between it and the cylinder wall that made it seem stuck. With a little bit of pulling I got the piston out pretty easy. I’ll attach some pictures of the carnage, I’ve never seen anything like it ESPECIALLY on a name brand saw, has to be operator error, maybe they put straight gas in it?

Spark plug looks insanely lean, so does the piston face, but somehow the connecting rod is still in place and it’s seems “ok” ish. I may clean it all up and check the bearings for play and then throw an aftermarket cylinder kit on there and see it it works… it was a free saw anyway!

Any thoughts on what happened, and if you think the lower end is savable as is? From what my friend told me the saw made a loud bang and locked up pretty quick… hoping that because it stopped turning so fast none of the metal chucks made it to the bearings…. Surprisingly the small end wrist pin bearing is still in tact as well as the wrist pin!

 

[2-StrokeDude]

First off, thanks for the response and advice! And upon farther inspection the piston is not fused to the cylinder wall, there was a chunk of piston wedged between it and the cylinder wall that made it seem stuck. With a little bit of pulling I got the piston out pretty easy. I’ll attach some pictures of the carnage, I’ve never seen anything like it ESPECIALLY on a name brand saw, has to be operator error, maybe they put straight gas in it?

Spark plug looks insanely lean, so does the piston face, but somehow the connecting rod is still in place and it’s seems “ok” ish. I may clean it all up and check the bearings for play and then throw an aftermarket cylinder kit on there and see it it works… it was a free saw anyway!

Any thoughts on what happened, and if you think the lower end is savable as is? From what my friend told me the saw made a loud bang and locked up pretty quick… hoping that because it stopped turning so fast none of the metal chucks made it to the bearings…. Surprisingly the small end wrist pin bearing is still in tact as well as the wrist pin!

 

[Bob Hedgecutter]

In my opinion- the saw was never straight gassed to cause that kind of failure.
If it had been, the top of the piston and the rings would be welded/fused as one. In your photos it looks like the rings are still free to move in the lands.
Also the large bash mark in the lower transfer looks like something caught there between bottom of piston skirt and cylinder- possibly breaking the first bit of piston and cracking the wrist pin boss.

Looks to be quite a bit of carbon top of piston and combustion chamber of cylinder- chunks of hot carbon can be an issue- but I think you have had a bearing, wrist pin, or piston ring location pin failure- a piece of hard steel floating around the fast moving bits that has not made it past the piston during operational speed.

By the flecks of metal evident in your photos- Id say the bearings in the bottom end are full of debris that will cause failure sooner than later and it may be a part of one of those bearings that caused the whole issue- they need flushed and checked really well.

Personally I would call the cylinder toast- but it needs well cleaned to make that call and before throwing a piston at it and calling it good.
All debris, carbon and transfer need to come out and any nicks, grooves and chips in the plating investigated.

Free saws are usually free saws for a reason.

 

[2-StrokeDude]

In my opinion- the saw was never straight gassed to cause that kind of failure.
If it had been, the top of the piston and the rings would be welded/fused as one. In your photos it looks like the rings are still free to move in the lands.
Also the large bash mark in the lower transfer looks like something caught there between bottom of piston skirt and cylinder- possibly breaking the first bit of piston and cracking the wrist pin boss.

Looks to be quite a bit of carbon top of piston and combustion chamber of cylinder- chunks of hot carbon can be an issue- but I think you have had a bearing, wrist pin, or piston ring location pin failure- a piece of hard steel floating around the fast moving bits that has not made it past the piston during operational speed.

By the flecks of metal evident in your photos- Id say the bearings in the bottom end are full of debris that will cause failure sooner than later and it may be a part of one of those bearings that caused the whole issue- they need flushed and checked really well.

Personally I would call the cylinder toast- but it needs well cleaned to make that call and before throwing a piston at it and calling it good.
All debris, carbon and transfer need to come out and any nicks, grooves and chips in the plating investigated.

Free saws are usually free saws for a reason.

That's what I was thinking, and yeah I didn't have high hopes for this saw, if anything I can always part it out on eBay. I would like to get the 361 going, so I may end up splitting the cases and replacing the crank, bearings, and cylinder and piston. Then I should have a solid saw... any advice on splitting the cases, and how to seal them up after? Is there just a gasket that goes between the cases or is it that RTV gasket maker type stuff?

Also do you think its worth messing with splitting the cases and replacing all that stuff? I mean it was free, granted a piece of junk as is, new OEM crank is around $60-$70 on eBay, bearings probably $20-$30, seals $15-$20, piston cylinder $50-$60? So total maybe $150-$200 in parts...

Personally I would love to have a good Sthil saw, the 361 seems like a really good power to weight ratio and size. However with how expensive Stihl saws are like $800-$900 dollars new for a good mid range one I've never been able to justify it for my uses. I personally repair small engine equipment on the side and restore vintage mopeds and small motorcycles and such so I have a decent amount of mechanical experience. Do you think it is worth it?

 

[Bob Hedgecutter]

Its a balancing act.
There are several ways to go about it, cheap aftermarket, secondhand OEM and new OEM.
You have to balance what is needed versus what can be saved, what the needed costs and your time- all weighed up against current secondhand MS 361 running saw prices.
It does not take real long before throwing parts at a well used saw tips the scales ahead of the latter.

You need to flush, clean and inspect the bottom end real well and make a judgement call. Push the rod big end side to side and see if any bearing cage is missing if it is and that did your piston in- it will do it again to a new top end. Easier to burn money in your fire.
Same with the main crank bearings- rotate the lobes and try to see if any bits are missing on the inner face of the bearings- if the cage is broken or the balls misaligned.
You ideally want to avoid splitting the cases- thats when the serious dollars come in- Stihl bearings and cranks are not cheap.

There is a gasket on the join and RTV has NO place in the saw repair tool list- proper liquid gasket maker, however, does. You do not have to use the liquid stuff with the gasket- but it can help hold things in place during assembly.
Cases can be split with heat and a rubber mallet- or you can buy proper Stihl case splitting tools- or their Asian knock off counterparts.
Bearings go on and cases go back together with the good old cold and heat tricks.
It is not working for NASA nor going to the moon- but it does have some tricks that can make the job easier. You just have to weigh up where the line gets drawn in the sand.