Stihl MS291

[macdven]

Hi Everyone and Merry Christmas.

I have a MS291. Sadly it was run hot by my brother in law and the cylinder/piston are cactus.

I’ve contacted Stihl and was told the throw it away and buy a new one as the repair cost is almost the same as a new unit.

After doing some research online, this seems to be true. With a saw only a few years old and, I am reluctant to turf it away. It’d be such a waste to throw away a nearly new saw; hence I’m posting here in search of some alternatives.

I looked for aftermarket parts on the likes of J&J, but no luck. Am I missing something?

Can I replace the engine with a MS391? They seem to be available.

Thoughts?

Mark (Australia).

 

[singinwoodwackr]

Hi Everyone and Merry Christmas.

I have a MS291. Sadly it was run hot by my brother in law and the cylinder/piston are cactus.

I’ve contacted Stihl and was told the throw it away and buy a new one as the repair cost is almost the same as a new unit.

After doing some research online, this seems to be true. With a saw only a few years old and, I am reluctant to turf it away. It’d be such a waste to throw away a nearly new saw; hence I’m posting here in search of some alternatives.

I looked for aftermarket parts on the likes of J&J, but no luck. Am I missing something?

Can I replace the engine with a MS391? They seem to be available.

Thoughts?

Mark (Australia).

a repair shop will tell you that and they are correct. Cost to have it done isn’t worth it.
you can do it for the parts cost. Get the IPL and manual from the ‘beg for manuals’ thread and have at it. Take your time and have fun.

looking at your pic I don’t see any gouges, just transfer, the cly may clean up fine. Meteor piston kit and be done.
lots of how-to here and YouTube.

 

[macdven]

Yes, same case, different p&c.
a repair shop will tell you that and they are correct. Cost to have it done isn’t worth it.
you can do it for the parts cost. Get the IPL and manual from the ‘beg for manuals’ thread and have at it. Take your time and have fun.

looking at your pic I don’t see any gouges, just transfer, the cly may clean up fine. Meteor piston kit and be done.
lots of how-to here and YouTube.

Thanks for your reply Singinwoodwckr.

Even if I did the work myself, a new Stihl bottom end is 3/4 the cost of a new saw - about AU$850. Seeing as I can’t find any aftermarket MS291 cylinders, I’m thought to look at the MS391 (which is avail aftermarket for way less).

I wasn’t sure if you meant the MS391 could be used. I’m keen to find out if it simply bolts in without any mods … or if it requires changes, including other mods like carby etc.

Ideally, if I could find an aftermarket MS291 cylinder and piston, that’d be the easiest.

 

[cscltd]

Ms391 will not fit- totally different saw even though it looks same. (Bigger zerox copy)
ms271 shares ms291 platform but there are 2 different engine designs with different pistons. The screw on manifold (earlier ) and later clamp on. The later being harder to find in aftermarket as moment.

 

[stihltech]

The question is, what does he crank and bearings look like? If OK, many AM pistons on the internet. Not a fan, but I understand a price restraint. I agree the cylinder looks salvageable.
Depends on your saw repair comfort level.

 

[singinwoodwackr]

Thanks for your reply Singinwoodwckr.

Even if I did the work myself, a new Stihl bottom end is 3/4 the cost of a new saw - about AU$850. Seeing as I can’t find any aftermarket MS291 cylinders, I’m thought to look at the MS391 (which is avail aftermarket for way less).

I wasn’t sure if you meant the MS391 could be used. I’m keen to find out if it simply bolts in without any mods … or if it requires changes, including other mods like carby etc.

Ideally, if I could find an aftermarket MS291 cylinder and piston, that’d be the easiest.

I goofed, sorry…was thinking 290/390, not 91

 

[macdven]

The question is, what does he crank and bearings look like? If OK, many AM pistons on the internet. Not a fan, but I understand a price restraint. I agree the cylinder looks salvageable.
Depends on your saw repair comfort level.

Thanks. The cyl is not salvageable - that’s the issue.

 

[TheJollyLogger]

Thanks. The cyl is not salvageable - that’s the issue.

Is it cracked?

 

[singinwoodwackr]

Thanks. The cyl is not salvageable - that’s the issue.

gouged? cracked? from that pic it looks like just Al transfer.

 

[macdven]

Is it cracked?

Nope, not cracked, just badly scored.

 

[farmhard]

I’ve contacted Stihl and was told the throw it away and buy a new one as the repair cost is almost the same as a new unit

Stihl can't fix Stihl's because they don't stock parts.
There is another option, you could try to sell the saw online and get some of your money back.
If you do go the route of a Meteor piston make sure you wash and blow out the case very well, i always throw in a set of seals at the very least. There was metal inside so if you don't get it ALL out you may damage the new parts. The grit will settle in corners and around bearings.

 

[BeatCJ]

Nope, not cracked, just badly scored.

@macdven, like said above, it doesn't appear your cylinder is scored. It appears that aluminum from the piston has transferred to the cylinder. The cylinder is cast aluminum with a harder coating/plating of "Nikasil". That aluminum transfer is relatively easily removed. Many people use an acid or a caustic to remove it. I have done it using an arbor, emery cloth and cordless drill. I like that method better because I don't have to worry about errant drips or pinholes in the coating causing damage to the cylinder. Then you only need to replace the piston and rings. That also assumes that the bearings and seals are otherwise OK. A quick search turns up piston and rings at varying prices, from $19.95 to $65, for me here in the PNW of the U.S. of course. I also see cylinder kits, but in my opinion for more than the value of the saw.

If you took the saw apart for the photo, you can replace a piston and rings.

But I would ask, do you know how/why the saw overheated? Whatever caused that will need fixed, too.

 

[farmhard]

Personally I'd be looking for on on the interweb needing a coil or starter rope.

 

[TheJollyLogger]

Is it cracked?

Then why do you say it's not salvageable?

 

[irhunter]

There were two versions of the 291. The early style, with bolt-on intake, is way easier to find AM pistons for than the late clamp-on style.

It sort of feels that the OP just really really doesn't want to clean up the cylinder. If that's the case, I would think parting it out/selling would be the way to go.

Roy

 

[HarleyT]

For reference, the ms271 and the ms291 are the same saw except for piston size.

 

[Jeffrey F.]

I don't think lower end is bad. Usually the cylinder is first to go when gas ran. Aluminum has a lower melting point than steel. I would take some Muriatic acid to clean cylinder out. Errant drips won't harm anything just be careful. Neutralize with baking soda water mix or straight baking soda. Meteor makes great parts, piston and rings. In the say 30 seconds it took to cook it, take the time to clean it. My MS290 is my go to saw for all around stuff. just do muffler mod, retune, and Bob's your uncle!

 

[farmhard]

take the time to clean it.

It would likely be far better than anything you can buy a/m. Go bills!

 

[TRTermite]

The saw is yours to do as you wish.
The Advice above is good and free as well. I think if you research Mastermind on UT he has 2 great videos that should help ease your skittish tendencies. What have you got to lose? A Dremel and a split arbor and various grits of emery cloth will clean the aluminum transfer stuck to the nikisil plating. Be careful not to mistake an aluminum buildup for a gouge/score.

 

[Lightning Performance]

If the thing needs bearings and seals your better off selling the parts or as a parts peice.
What cooked it?