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 iit 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.