MS 261 cylinder and piston replacement

Greenhighlander · May 10, 2020, 07:47:30 AM

I bought this saw 7 years ago and after a couple years of firewood duty it ended up with a badly scored cylinder and piston. Sadly the shop quoted me almost the same cost to fix it as to buy a new one.
My questions are , how difficult is it to replace both myself? am I better off saving up and buying a new one?

Cheers

dougand3 · May 10, 2020, 09:48:47 AM

Hard to say w/o knowing your wrenching ability. If you can pull the carb off, you can replace the topend. Lots of how-to youtube videos. Be a good learning experience for low cost - a new AfterMarket P&C kit is ~$30. If you mess it up, that's low tuition in the school of self taught. If you get it right, you've got a running saw. Will it be as good as OEM or Meteor topend ($200-$400)? Maybe not but could be close.

Also, why did it score? straight gas, rock ingestion, tuned too lean...are fine for just a topend. Crank seal leak is much deeper repair.

Greenhighlander · May 10, 2020, 10:42:18 AM

Quote from: dougand3 on May 10, 2020, 09:48:47 AM
Hard to say w/o knowing your wrenching ability. If you can pull the carb off, you can replace the topend. Lots of how-to youtube videos. Be a good learning experience for low cost - a new AfterMarket P&C kit is ~$30. If you mess it up, that's low tuition in the school of self taught. If you get it right, you've got a running saw. Will it be as good as OEM or Meteor topend ($200-$400)? Maybe not but could be close.

Also, why did it score? straight gas, rock ingestion, tuned too lean...are fine for just a topend. Crank seal leak is much deeper repair.

Thank you for the reply.
My wrenching ability is very limited when it comes to chainsaws. That is exactly how I am looking at it. Would be a good learning experience.
With a lack of good dealership or saw shop support I have figured I midas well learn on my own.
My best guess at why it scored is using regular instead of supreme gas combined with using the regular gas mix that was also a number of months old .
The tune seemed fine right up until just before it went into beast mode and died.
Is there a way to check for the crank seal leak before I try to order the top end parts?

sawguy21 · May 10, 2020, 11:07:15 AM

That should not cause a major failure by itself. Best to have the saw pressure/vacuum tested to check for an air leak before tearing it down and avouid destroying a new top end.

dougand3 · May 10, 2020, 11:09:51 AM

Sounds like it died lean. Your fuel mix answer is kinda iffy. Intake boot is another leak possibility - inspect carefully.
Pressure/vacuum test crankcase - kinda involved. Rubber blocking intake and exhaust ports. Adapt a spark plug to be an air tube. Check youtube.
An easier but less deep crank seal check - Clean and dry seals behind flywheel and clutch. Rotate piston to top. Pour fuel mix in intake port so it's above cylinder-crankcase junction. Look for leakage - no obvious leak, then set saw on clean white towel and look hours later.

Greenhighlander · May 11, 2020, 06:48:00 AM

Thank you for the replies. Gonna take it apart this weekend and see what I find.

Tom King · May 11, 2020, 10:15:48 PM

It's not worth the time to do anything to it without pressure testing it first. If the crankcase can hold pressure, replacing the cylinder, and/or piston is a pretty simple job that requires very few tools even. Without the pressure test, it's just guess work.

Greenhighlander · May 17, 2020, 08:26:32 AM

Quote from: Tom King on May 11, 2020, 10:15:48 PM
It's not worth the time to do anything to it without pressure testing it first. If the crankcase can hold pressure, replacing the cylinder, and/or piston is a pretty simple job that requires very few tools even. Without the pressure test, it's just guess work.

I can't find anyone to do a pressure test for me without also getting them to do all the repairs.I simply can't afford to do that right now. Especially given that the repair costs quoted was pretty close to the cost of a new one.

Tacotodd · May 17, 2020, 04:46:31 PM

This saw does require 89 or BETTER octane fuel, so that part didn't help, non-ethanol gas is best. This is is from my own, and personal, sad experience. Don't ever let anyone else buy your gas for you. You never can be sure what they will get. Start it up, let it come down to idle, take your brake parts cleaner and squirt some at the seal area in question. If it dies, there is a place that needs attention. In not, then questions remain.!?

Tom King · May 18, 2020, 09:22:19 AM

Quote from: Greenhighlander on May 17, 2020, 08:26:32 AM
Quote from: Tom King on May 11, 2020, 10:15:48 PM
It's not worth the time to do anything to it without pressure testing it first. If the crankcase can hold pressure, replacing the cylinder, and/or piston is a pretty simple job that requires very few tools even. Without the pressure test, it's just guess work.
I can't find anyone to do a pressure test for me without also getting them to do all the repairs.I simply can't afford to do that right now. Especially given that the repair costs quoted was pretty close to the cost of a new one.

If you're going to work on saws, one of these is good to have:
https://www.harborfreight.com/mityvac-vacuum-pump-39522.html
You don't have to buy many parts you don't really need before this is paid for.

In need of education? There are always several youtube videos available:
https://www.youtube.com/watch?time_continue=37&v=t4DQSKj4FrM&feature=emb_logo

You will need a few tools, like a flywheel puller, but those cost a few cents over 8 bucks, and you only have to buy it once. They're easy to use.
https://www.hlsproparts.com/small-engine-tools-s/136.htm?searching=Y&sort=2&cat=136&show=36&page=4

Don't buy the seal puller. The best, and fastest seal puller is a cotter pin puller. I have a thread on this forum with pictures.

farmfromkansas · June 03, 2020, 10:48:35 PM

My stihl dealer said the 260's score cylinders more than other models because of the higher speed. Said they have fewer problems with 290's, which are about the same price. He takes trade in's of old saws, parts them out. I had an 026 with scored cylinder, he gave me 100$ against a new 291.

realzed · June 03, 2020, 11:11:47 PM

Sounds like you certainly could have used a new dealer who could have helped you out, instead of firstly helping out himself!

Greenhighlander · June 04, 2020, 06:27:43 AM

Quote from: Tom King on May 18, 2020, 09:22:19 AM
Quote from: Greenhighlander on May 17, 2020, 08:26:32 AM
Quote from: Tom King on May 11, 2020, 10:15:48 PM
It's not worth the time to do anything to it without pressure testing it first. If the crankcase can hold pressure, replacing the cylinder, and/or piston is a pretty simple job that requires very few tools even. Without the pressure test, it's just guess work.
I can't find anyone to do a pressure test for me without also getting them to do all the repairs.I simply can't afford to do that right now. Especially given that the repair costs quoted was pretty close to the cost of a new one.

If you're going to work on saws, one of these is good to have:
https://www.harborfreight.com/mityvac-vacuum-pump-39522.html
You don't have to buy many parts you don't really need before this is paid for.

In need of education? There are always several youtube videos available:
https://www.youtube.com/watch?time_continue=37&v=t4DQSKj4FrM&feature=emb_logo

You will need a few tools, like a flywheel puller, but those cost a few cents over 8 bucks, and you only have to buy it once. They're easy to use.
https://www.hlsproparts.com/small-engine-tools-s/136.htm?searching=Y&sort=2&cat=136&show=36&page=4

Don't buy the seal puller. The best, and fastest seal puller is a cotter pin puller. I have a thread on this forum with pictures.

Thank you. That is some really great information .

Quote from: realzed on June 03, 2020, 11:11:47 PM
Sounds like you certainly could have used a new dealer who could have helped you out, instead of himself!

That doesn't exist here from what I can tell. I bought a brand new 395xp after saving up for years and still can't seem to get service after dropping $2000 at his shop. Took it in after breaking it in he started it up, revved the pith out of it 3-4 times and said yup seems good. Dropped my little 445 off 3 weeks ago now because it wasn't running quite right, was told " I will take a look in a couple days " . Haven't heard a thing since.
Thats why I figure I midas well try to learn myself.

Again thank you all for the great info. I am super busy with other things right now but do plan on trying to do this at some point.

Tom King · June 04, 2020, 08:55:40 AM

That's the reason I've learned to work on stuff myself. I can take my time, do the whole job right, and it still takes less time than finding someone else to try to do it, and then have a high chance of having to get it redone.

sawguy21 · June 04, 2020, 11:12:44 AM

I worked in shops and strived to do it right the first time, I took pride in my work and comebacks cost time and money. Unfortunately not all mechanics or their bosses are conscientous and mistakes are made at the best of times but there is no excuse for ignorance. It sounds like the people some of you are dealing with don't know or just don't care. The local Stihl dealer, our own Paul_H knows his saws has been around loggers all his life and his tech is a whiz on them but it seems shops like that are rare.

Demetrio · June 04, 2020, 05:12:56 PM

Hi Greenhiglander, have you noticed any change in the engine recently? Since you can't pressure test the cranckcase you can alternatively check the spark plug color. You should be able to tell if the tuning was fine before it died (lean --> whitish, ok-->hazel, rich-->black), unless you had a sudden leak (unlikely though). You can also remove the exhaust and visually check inside the cylinder to see if there is any sign of mechanical failure (I had to replace the top end once to my 261 due to a piston pin circlip failure).