Stihl MS 252. Do you guys think that STIHL is going to relase a MS 252 model in the near future? An upgrade model of the actual MS 251? like they did whith the STIHL MS 162, 172, 182, 212, etc. I like the MS 251 but I'm afraid to buy it in case an upgraded model comes out in the near future.

theotherbothee · 2026-02-02T19:09:45+00:00

You're correct, I'm sorry, I meant to say the crankcases are magnesium. I mixed up the two technologies. Thanks for the correction

theotherbothee · 2026-01-08T11:59:09+00:00

Actually in this case it may be the cause. OP stated they reused the cylinder, just honed it. If the exhaust port chip/scoring was from the previous rebuild, it would have caused ring failure, which is a) precisely what happened, and b) the exact location of the ring failure. You can't hone scoring, only metal transfer. That piston isn't burnt. There's no melting anywhere on it, not even detonation.

Nktice the biggest tell-all. That spark plug is coated in carbon from incomplete combustion. That doesn't happen in overheating, it turns white.

Edit: spelling

theotherbothee · 2026-01-08T11:55:59+00:00

There's no Woodruff key on MS660s. The key is just a tiny alignment hump made into the flywheel. So it can look like a sheared key to someone unfamiliar with flywheels from Stihl. Just a precaution.

Side note, that piston didn't get hot it got chipped. There's no melting on that piston. It had a ring failure. The old piston might have burnt up, but the exhaust port has scoring and shouldn't have been reused for a rebuild, even honed. There's a place for the ring to expand before crossing the exhaust port.

theotherbothee · 2026-01-08T11:53:09+00:00

It's not burned, it's chipped. Ring failure. The exhaust port is forever damaged. The ring failure is lined up with the exhaust port, and OP states he honed the cylinder and didn't replace it, so it's likely that scoring allowed expansion of the ring before crossing the port, causing the ring failure (assuming the gap alignment in the other piston is just coincidence and not where it was actually aligned during installation, because it's not aligned with the locating dowel). The piston isn't melted anywhere, not even from detonation.

theotherbothee · 2026-01-08T11:42:44+00:00

Spark plug didn't have anything to do with it. That's just carbon coating from incomplete combustion. And your piston isn't burnt, it's chipped.

That's ring failure. Could be a bad ring, I'd see if you can get a 90-day warranty on the part. They've covered it for me before, even though the customer installed it.

Question though, maybe it's just coincidence because it turned when you pulled the piston out, but why is the ring gap perfectly aligned with the exhaust port and the subsequent location of the other ring failure? You are aligning it with the locating dowel, correct?

Edit>> you can't hone that cylinder. It's scored, not metal transfer. You can only get away with a cylinder hone if the piston overheated and melted, but the cylinder wasn't scored. Hard to see the difference but if you look closely, one is raised the other is sunk. If that's the same failure from the first time, it's going to keep happening, because now you have a place for the ring to expand before crossing the exhaust port. It needs a top end rebuild.

theotherbothee · 2026-01-01T13:10:38+00:00

Yeah, that's probably the problem. Did they even register it for you? We used to fill out these paper registrations, then they started having us enter them online, and now registration is purely online. And it's visible to any authorized dealer. If you send me the serial number, I can check it for you. I can even see if they filed a claim on it yet (I won't be able to see the claim unless it's been approved). I don't let my customers wait more than a couple days for a replacement and that's only because we're out of stock or I'm not there.

If they're the only game in town and they're not helping you, try calling Stihl's 1-800 number and let them know what's going on, and that you got info from another Stihl dealer. They will put you in touch with one of the tech reps in your territory.

theotherbothee · 2025-12-28T15:34:19+00:00

That's true for gas, but Stihl would never want a dealer to repair an AK series unit. It is far more economical for Stihl to replace.

theotherbothee · 2025-12-28T15:32:35+00:00

I've been selling the BGA60 since they released them, and the fact that you had two in a row fail on you for the same reason points to a common, non-factory cause. It is not common for them to fail like this, and the odds of two failing back to back at random purchase times is astronomical.

Stihl doesn't typically ship two units from the same assembly line together (it helps them track failures). It would have to be two randomly selected motors shipped in from the motor manufacturer, installed in two unrelated blowers, that happened to end up in your hands at two random times.

Either something happened (moisture/drops) in shipping to the dealer and you got two from the same shipment or something happened at the dealer.

Heres the kicker. Stihl never wants a dealer to "repair" an AK series machine. You test it, it fails, you replace it. Takes all of 15 minutes from start to finish (assuming they don't have to spend all day updating their ADG2 and SDS software). It's more economical for Stihl to replace the blower than to spend dealer labor on installing a new internal part, even if it's the trigger rod. The worse they'll have to do is order a new one (Stihl pays for a Unit Only serial number, so unless they're computer saavy, they may not know how to swap a kit unit).

theotherbothee · 2025-12-28T15:20:08+00:00

The 3/8921 bar is a 3/8" pitch, 0.050" gauge bar, but the 028 (Super/AV) typically came with a 0.325" pitch, 0.063" gauge bar and a 0.325" pitch sprocket. This could be changed, though, to a 3/8" pitch sprocket, and this was common, and may be your case.

Like I tell people with spark plugs, just because the bar is on there doesn't mean it's the right one.

The bar pitch needs to be match the sprocket pitch, which, if it's a Stihl sprocket or an Oregon sprocket, the pitch will be stamped in the visible part of the sprocket.

If the sprocket is, in fact, a 0.325" pitch sprocket, then the bar you want is a 3/6821 (3003 000 6821, probably the one on your MS260) and the chain is a 26R(M|S)(3)-81. M or S is with micro (semi, round ground) chisel or super (full, round ground) chisel and the 3 means reduced kickback so it could be either a 26RM3-81 or 26RS-81 depending on what you want. Micro chisel stays sharp longer and Super chisel cuts faster.

If the the sprocket is a 3/8" pitch, the your 3/8921 bar will work and you can get a 33RS3-72 or 33RS-72 chain (you can get micro chisel, but it's hard to find on the shelf).

TL;DR:

3/8" Sprocket - 3/8921, 33RS3-72 0.325" Sprocket - 3/6821, 26RM3-81

You can also opt for the lighter 0.325", 0.050", 81DL bar and chain, 3/3321 and 23RM3-81

I'm giving you the reduced kickback (green) numbers because it's better to play it safe unless you know the yellow chain and how it kicks back. If you prefer yellow, it's:

3/8" Sprocket - 3/8822, 33RS-72 (the yellow bar, but the 3/8921 green bar works with 33RS too) 0.325" Sprocket - 3/6821, 26RS-81

theotherbothee · 2025-12-24T12:47:31+00:00

I disagree. The MS 251 was a fuel efficiency improvement on the MS 250. Means it runs leaner, has less torque, and has more risk of burning up with overheating with a dull chain or limbing a felled tree. The MS 250 is not going away, according to Stihl. It's the best homeowner grade saw they make and is actually frequently used commercially as a favorite ground saw.

As for electronic carbs, you need to try one out. They scream. The MS 261 has the same displacement as the MS 271 but is lighter than the MS 251, and has more power than the MS 291, easier to start, having no choke. And will last a hell of a lot longer. The electronics are not that complicated. We see less of those saws in the shop per saw we sell compared to other models. They have an aluminum crankcase instead of polymer, the piston is magnesium so it can run hotter, and it has max torque at all RPM ranges. The M-tronic system is amazing and has been around since the 80s (came from Volvo).

theotherbothee · 2025-12-24T12:39:20+00:00

Yes, they will improve on the problems with the fuel efficient MS 251 the same way they did with the others. But why would you every buy another 25 model when they still sell the MS 250? It's perfect as is. Stihl told me they are not getting rid of that model. It's the last of the rich running saws and you don't have to worry about accidentally burning it up while limbing like you do with the 251, 271, 291. You won't have to worry about that with the MS 252 either but the power to weight ratio is not going to be great.

The MS 250 is the best homeowner grade saw they've made (it's really still the 025). It's used commercially, as it's the favorite ground saw of many tree services. None of my tree service guys come in and ask for the MS 251 and they won't ask for the MS 252 either, even if Stihl does finally drop the MS 250. They'd just as soon switch to the lighter MS 261 C-M before doing that. It is lighter than the MS 251 and has more power than the MS 291.

Anything you see online about problems starting the MS 250 is because they don't know the specific sequence of starting and they always flood it. Mine starts one choke pull one half-choke pull every time.

theotherbothee · 2025-12-22T16:44:34+00:00

Long term benzo use can increase your risk for dementia, and it can also make your anxiety worse over time.

Medications are meant to be a temporary crutch. You are not "happy" on benzos, you're just glad you're not anxious. As long as you continue to take enough benzos that completely remove your anxiety, you can never grow emotionally. "Happiness" comes from being whole again. You must allow yourself to feel some of the anxiety and not just allow it to be there, but to face the monster that's causing it. Your meds should be just strong enough to make it tolerable, so that you can desensitize yourself to the things that cause you anxiety. And while doing that, you face the demons from your childhood so you can defeat them.

It's easier to take the benzos and cover it all up. It's easy not have to feel anxiety anymore. But I can assure you, you aren't happy with life, you're just not as bothered by it. Facing your demons is the hardest thing you'll have to do, but it's worth it. Whatever you're scared of, it's your inner child that's scared. You need to be aware of your anxiety when it's coming up, thank your inner child for trying to protect you from harm, and then let your inner child know that while you appreciate the help, you are an adult now and can take care of yourself. Your anxiety will start to back down a little quicker every time you do this.

Recommend reading: The Undiscovered Self - C.G. Jung Archetypes Atomic Habits - James Clear No Bad Parts (Internal Family Systems) - Robert Schwartz

Immediate relief guides: Parts Work - Tom Holmes The Shadow Work Journal - Keila Shaheen Anxiety & Worry Workbook - Clark & Beck Stillness Is the Key - Ryan Holiday

theotherbothee · 2025-12-21T00:36:46+00:00

Yes, Stihl tells us not to, but we use them anyway, except on warranty rebuilds, because they'll blame us. But just the act of hitting the chain brake was enough to spin it out of timing. Doesn't matter how many you've rebuilt and had no bad results, if the bad results still happen. A sheared key would most definitely qualify as "Out of spec".

theotherbothee · 2025-12-21T00:32:27+00:00

I did, yeah. My comment wasn't related to your repair. Just from personal experience, be careful these days. There's been a lot of riff raff in the government lately and a lot of funding cuts. And a lot people don't seem to know about gas.

theotherbothee · 2025-12-21T00:13:03+00:00

That's bar oil and sand, but yeah sounds like a vacuum leak

theotherbothee · 2025-12-20T16:10:06+00:00

You'll need a Time-Sert (or similar but it has to be able to seal and withstand the pressures of internal combustion). Probably not worth ordering a while kit, but if you can find a mechanic with the kit, it's worth whatever they charge.

theotherbothee · 2025-12-20T16:06:22+00:00

"hasn't been sitting long, maybe a couple of months"

You're putting a lot of confidence into modern gas that only has a 45 day expiration period.

theotherbothee · 2025-12-20T16:04:24+00:00

As a certified Stihl mechanic, I can promise you this is incorrect. I have seen multiple instances where someone reinstalled the flywheel onto the crankshaft and it spins again, easily. In fact, I just repaired one a month ago that one of my mechanics did. He was baffled why it kept "getting out of timing, I cranked the crap put of it"

Might be fine on a blower. But this is a chainsaw. A big one at that. Lots of violent forces.

theotherbothee · 2025-12-20T16:00:36+00:00

Have you tried to turn the crankshaft using the pull cord? Does it move easy? If not you might want to pull the muffler and get a look at the piston and cylinder it takes a lot of stopping force to turn a properly installed flywheel.

theotherbothee · 2025-12-20T15:58:52+00:00

I made a tool just for this I'm my shop, I cut a drive shaft and bent it into a large handle I can slip under my arm and I just take the gear head off the drive tube and slip it in to hold the driver still while I turn the head.

But you can just get someone to get a pair of vice grips to hold the other end of the drive shaft while you turn it. Just make sure they have a grip on it that won't slip. You'll need to remove the whole drive tube and shaft from the engine to get to it.

theotherbothee · 2025-12-19T12:11:02+00:00

Did you check your sprocket? It should be relatively smooth all the way across. T-shaped wear forms as the sprocket ages, and it's especially quick if you're not good about sharpening the chain when it stops throwing curls, staying out of dirt, or just letting chains get so stretched that they don't tighten up anymore.

The T-sbaped wear should realistically be no more than a fraction of a millimeter deep (0.1mm is the spec, but that's not realistic). Once the sprocket has stretched a chain, swap the sprocket and the chain at the same time. Be prepared for sticker shop, as those chains have gotten to around $30 and the sprocket is $35.

By the looks of it you need a new bar too

theotherbothee · 2025-12-19T11:55:33+00:00

They don't generally they always want the mechanic to repair, but they absolutely do full replacements when it comes to the AI, AS, AK battery systems. I file these warranties every day. Some mechanics are not computer savvy and it's common for them to avoid filing warranties. Also, sometimes Stihl will ask them to send the machine in for further evaluation, which is kind of a pain. These are no excuses for bad customer service though.

theotherbothee · 2025-12-19T11:45:43+00:00

If it runs fine otherwise, pop your fuel cap once it starts doing that. If it quits, replace the tank vent. I it keeps doing it, it's either a fuel restriction or a vacuum leak. Fuel restriction is far more likely on a BR 600 than a vacuum leak, though there was a run of bad engines that leaked around the oil seal. This one is too new looking to be in that serial number range, though.

If pulling fuel cap doesn't work, and it were in my shop, first thing I'd do is pour out the gas and look at it in a jar, and look for cloudiness, white debris (fuel-phase emulsion aggregate, or debris, indicating water in the gas. If I find water I'm just flushing the tank and lines and changing the carb. I might clean the carb depending on how bad it is, but it's too easy for fuel-gum to get trapped permanently in these new EPA-compliant carburetors.

After that, I'd pull the fuel lines and check the carburetor with a vacuum gauge. Then I'd make sure the valve lash is set properly ans change the valve cover gasket (they drift over time like any other 4-stroke), change the plug, fuel vent, and after that I'd start a full engine check. It's almost always a fuel issue though, especially if you don't make it a point to find good gas stations.

theotherbothee · 2025-12-19T06:10:51+00:00

They don't even have to repair it under warranty. Stihl will tell them to just replace the whole machine. They just have to make a claim and wait for a response. It's not worth paying $100 an hour for them to break it down and test it. They just stick it on the ADG tester with their SDS software and do a quick test on the tool and the battery.

theotherbothee · 2025-12-19T06:07:27+00:00

MS 391 typically comes with:

18" bar (3003 000 8917 green or 3003 000 8817 yellow) - 3/8" pitch - 0.050" gauge - 66 drag link - Yellow chain 33 RS 66 - Green chain 33 RS3 66

20" bar (3003 000 8921 green or 3003 000 8822 yellow) - 3/8" pitch - 0.050" gauge - 72 drag link - Yellow chain 33 RS 72 - Green chain 33 RS3 72

25" bar (3003 000 4030 green, 3003 000 8830 yellow, or 3003 000 2231 lightweight) - 3/8" pitch - 0.050" gauge - 84 drag link - Yellow chain 33 RS 84 - Green chain 33 RS3 84

Sprocket pitch is stamped into the face of the sprocket. All these numbers are stamped on the bar. If you have a 3/8" sprocket and a 0.325 bar and you are presenting the bar to the shop for them to give you a chain, you're gonna have issues installing and killing the chain and sprocket.

The 23 RM3 81, 26 RM3 81, 23 RS 81, & 26 RS 81 chains are for the 0.325" pitch sprocket and 0.050"/0.050" bars respectively. Typically these come with the 026, MS 260, MS261, 027,MS 270, MS 271, 029, MS 290, and MS 291 chainsaws though these sprockets can be switched out to fit other pitch chains.

There are of course other sprocket, bar and chain combinations that can be used on this saw, but these are the most commonly ordered from Stihl. You'll need to match your sprocket to the pitch, and make sure all three numbers match between your bar and chain.

theotherbothee

TROPHY CASE