Stihl MS 660 questions

[KittycatUsingPowertools]

Hello! This might going to be a long post, but please bear it with me. So, first of all, our story starts at the time my husband wanted to get a big saw finally (he has a 50 something cm³ for firewood cutting), he is a woodworker, he has all sorts of logs laying around in our garden to slice them up. So after contemplating for a while what to get, an used MS 660 or a new chinese clone kit of the MS 660, he went for an used one. Looked at various sites here - a small central european country - and found a good looking one on pictures, sounded nice for our untrained ears on video, so he bought it, it was located at the other side of the country, so we couldn't personally check it out. Fast forward a few days later, it arrived, it was running all nice, only the brake not exactly engaging, but with every used tool we have bought before, he wanted to take it apart anyway to check out everything. Obviously buying used tools always carries the risk of not receiving exactly what you are expecting, and we kinda received what he paid for.

So, he took it apart, and with closer inspection, found a lot of issues. At this point I don't know if we can get back some money or not, but I'm looking into the future rather than being angry at the whole situation.

The main issue is the crankcase, it has several holes stripped, the brake bar stud is on the run (read a lot, and I mean A LOT about MS 660s, I know this is kinda a common issue with Stihl saws) and the clutch side generally looks cooked and damaged. What's still original on the clutch side, it looks like someone run it dry and had a chain breakage, probably that's why the cooked look and chipping paint, making the thing overheat the body and chain. The clutch, oil pump and piston and cylinder are all aftermarket things. And the next big issue is the p&c being only 52 mm, basically being an MS 650 instead of the 660. The cylinder is Hyway, the piston is completely unmarked, probably the same Hyway, but at this point no one knows.

If you have read my post this far, thank you very much, we are at the good part now where I'm actually going to ask the questions!

So, no.1 question, does the aftermarket crankcases are any good? Or are there any "brands" which are compareable with the original somewhat at least? I could find original new Stihl cases locally, being 3 times the price of aftermarket ones, so yeah, I would plan a purchase very carefully and accordingly. I want a good, sturdy case, buying an used original is also an option within Europe, but I'm understandably wary of used parts now.

Question no.2, the compression is pretty terrible currently, being only between 105-110 for some reason. The piston looks fine, the rings on it looks fine, he poured oil on top of the piston to check if the rings are sealing better with oil, compression stayed the same, so they seem to work still. It died a few times after letting go the throttle. The oil seals are allegedly new, but he haven't teared the machine down that far. We might get a new decompression valve, that might be the issue, but if not that, what else to check?

Question no.3, the piston and cylinder set being already aftermarket, what is the next best thing to get after an original set? I have read Meteor, but does it worth it to get the 56 mm kit? Or 54 mm works just fine, and probably has a better timing than the current chinese one, so has a significantly better output?

So yeah, basically I'm Christmas present shopping and I want to get my husband *the good stuff* and make his life easier. I might have more questions to pop up in my head, but currently the crankcase and compression issues are the biggest problems. Thanks again for reading this stupid wall of text <3

 

[ZeroJunk]

My advice would be to go buy your husband a MS661 and be done with it. Many on here can resurrect the dead. But, you really have to have done it for a while. Stripped screw holes are not such a deal, but broken brake studs are something else. Chasing your tail comes to mind. Or, lipstick on a pig.

 

[pioneerguy600]

Question1) The AM crankcases with the bearings already installed have been used by many and I have heard no bad responses about them, I prefer to use OEM myself and will pay the extra costs involved to keep all my saws OEM, just the way I roll.
Question 2) Many times the AM pistons and cylinders have far too much room above the piston at top dead center, that space we call(squish) and it rules compression mostly, too large of a squish clearance and you have lower compression. The OEM piston and cylinders have a tighter squish area and make much more compression.
Question3) The OEM ,P&C will give the best results right out of the box, they will have better port timing, better squish and better upper transfer shapes and sizing, all that almost always makes better power and performance, the Meteor sets are some of the better made sets but not quite as good as OEM any of the rest of the AM sets are hit or miss, I have seen both good and bad sets from the same manufacturer so it is a toss of the dice whether you get a good set or a poor performing set. The 56 mm would make it a real 066.

 

[ZeroJunk]

Well, if he is up to it. What seems simple to some is impossible to others.

But whatever, new crankcase, new cylinder kit, whatever is going on with the brake.

So, you spend several hundred bucks and back in the same boat.

Unless he wants a new hobby, go buy a new saw. Or, piss away a few hundred bucks, and then go buy a new saw.

 

[KittycatUsingPowertools]

Thank you all for the insights, sadly neither of us has the means to buy a new saw. That is why we were contemplating to buy an used MS660 or a new G660, because they are in the same price range at least here, locally. We sadly got unlucky with the used machine path. As I said, we have bought all sort of used tools and machines before, both of us are somewhat in the mechanic field, we can both fiddle in this kind of stuff, locate and recognise problems, fix those problems and make a working machine out of trash. But the fact that we got scammed, and basically the main parts of the machine are all AF... that's a fact I can't sadly change, we gotta live with what we have cooked for ourselves.

All this said, I don't have a lot of choice but to buy some more parts, because we do need this saw to work. Obviously played ourselves into a corner, this our first big loss on a machine we bought used. A 54mm (no one seems to carry 56mm here, best I saw was a 54mm pop-up) Meteor set would cost about 130$, more or less, depends on the dealer, and about 80$ for an AF crankcase. The OEM piston would cost 130$ itself, and I can't find an original cylinder in the country. The machine itself were about 450$, a 661 would be 1200$... so we have a long way to reach the cost of that. These prices doesn't even look that terrible in dollars, but our central european joke of a currency is in a very bad shape, so even for these stuff I have to save up.

 

[cookies]

File a chargeback through your bank or credit card for fraud and return the saw
you can order a new oem piston/cylinder on ebay for around 300usd, being your in europe there should be oem cylinder kits for less than oem prices in the states. There are a few companies that sell oem parts online in europe.

these saws in good shape are fetching 1000-1600 usd currently in the usa
like new are getting 1400-2000
A new kit saw will be about the same power as what your using now without some cylinder work

I had someone do the same crap to me recently, they tried repairing the saws themselves resulting in lean engine damage...sold as cranks and runs good. people are desperate from high costs out there.

 

[MacAttack]

I agree with the previous post that I'd try to return the saw and get your money back if at all possible. From what you described that saw has had a hard life and had been worked on by an incompetent person. Basically a lemon / money pit that you'll end up dumping more money into and still have problems. If it's got stripped holes on the outside you're probably going to find more problems on the inside.
Sorry for your situation!

 

[KittycatUsingPowertools]

I'm unsure about the policies banks have here for chargebacks, it's definitely not as simple as in the US. The saw works, he uses it for milling, he bought it for that, but the saw has it's ups and downs for sure and I don't know how much life it has left in it. Even being in this weakened state, it cuts through 2 years old dry black locust logs (between 30 and 70 cm wide, he uses it with a 90 cm chain and guide) like butter with a sharp chain.

There is one stripped hole under the clutch, one of the 4 screws holding the case together, it has been drilled and tapped deeper by the previous owner (who is actually not the guy we bought it from, he just resells them). So yeah, the case has a lot of problems, broken bits here and there, chain brake spring worn out the case, etc.

I might be searching Ebay the wrong way, but I can't really find OEM c&ps from EU, the one kit I found and actualy genuine is 500$.

 

[pioneerguy600]

It really sucks that saw prices are so high over there, I build chainsaws frequently from my spare parts supply and they cost me very little so that is why I often recommend repair over buying new. Shipping costs for sending parts over to Europe has become horrendous,especially since Covid. If I had the OP`s saw here I could rebuild it completely for less than $500 using all OEM parts , many I have pulled from damaged saws through the years that were determined to be too much damage to repair on a cost basis.Forestry machines running over or dragging a load over a chainsaw, the big machine comes out undamaged. I hope the OP can find enough good parts to get the necessary repairs done up on the budget they have to work with.

 

[ZeroJunk]

All the screws are wrong, which is curious.

Looks like you could make the brake work with a band and the spring.

You can tap 5MM to 12-24 SAE and 6mm to 1/4 -20 SAE. Just don't get carried away cranking down on them.

 

[cookies]

If you cant file a chargeback, cant afford a new saw and cant afford oem then just run it and when it gets weak throw a meteor kit on it and keep going...the hole missing a screw can have a helicoil installed with a new bolt. Find a auto repair shop or a machine shop and have them repair it or order a helicoil kit, the bolt was a m5 but I would assume you would need to go up a size to a M6. Do not cut threads into saw cases and put a bolt into it, the magnesium case is too weak to support the loose threads without a insert.
Sometimes making lemonade from the cow pies we are dealt is all we can do.

 

[ZeroJunk]

the magnesium case is too weak to support the loose threads without a insert.

Bull

 

[guym3]

Funny - I've just finished for the day in my workshop stripping down an abused stihl 066 with a similar story to yours. TBH they are a nightmare where everything you strip down you discover it was botched, rethreaded or a substandard part. I bought this 066 for stripping and porting heavily so I'm not bothered and paid very little for it. If it was my "only" big saw and I needed it to run now, rather than a bit of fun, then I'd take a very different view. I'd certainly echo the advice to return it if at all possible. It wasn't what was advertised so you should be able to do so.

I enjoy buying non-running ancient saws and getting them going, porting them and using them. It's sure a good way to learn about all the problems you can encounter. But if you aren't comfortable vacuum/pressure testing and putting in your own helicoils then it will be a road of pain.

I find Meteor pistons are very good (on Ebay from Italy) but none of the OEM cylinders are that great. Hope this helps and sorry to sound negative. You were talking about finding spare parts. I use L&S engineering in the UK who export to the EU. Look on their website (register to see all the parts diagrams) to see the part numbers you need. They also post really quickly and offer good on-line advice.

 

[stihltech]

OK, the first question, are YOU capable to do this work?
2) Never let a compression tester cause you to immediately down a saw. Piston and cylinder, crank and bearings visual condition are the final word.
3)So many things can cause a saw to not idle. The vacuum and pressure test are a must. Otherwise it is just a guess.
4) And maybe this should be first-used saw -sight unseen- get your money back. We even get caught in the shop occasionally. Salesman takes in a GOOD? saw, only to find major issues on the bench.

 

[ZeroJunk]

As far as tapping up a size. Going from 5mm to 12 is .205 to .216. Going from 6mm to 1/4 is .243 to .25
What is it you are trying to hold ?

I have a MS660 that I have used for years with a 1/4 -20 holding one side of the cylinder on . Does not seem to mind.

I repaired a MS201TC that had rattled the 5 MM muffler screws out with 12-24 a few months ago . Holding up fine with a tree service that could wreck an anvil with a spaghetti noodle.

And, I routinely replace the muffler screws in BR 600's and 700's with 12-24 after they get rattled out.

Hold up as well as what rattled out to start with.

So, use your own judgement. If you don't want to do it that way do it some other way.