Stihl MS 660 questions

[KittycatUsingPowertools]

Is the ring pin stop in the wrong place, or is that an optical delusion ?

This is the exhaust port side, the rings are in the correct position, just broken and stuck, I don't have a picture of the pin side.

Ouch! Did ring catch the ex port? Or did something from down below let loose, crank rod OK?

Piston looks well worn before the carnage.

Measure the piston to tell 650 from 660. Also is P/C OEM Sthil?

Looks like the ring caught the ex port, yeah. Rod looks ok but metal shards had fallen down into the crankcase, so further inspection is needed.

So I don't know how far have you read back about this saw, but it was sold to us as used 660 with OEM parts. Turned out that wasn't true at all, 52mm, cylinder is Hyway and piston unmarked, with a lot more AM parts.

We are going after the guy, but I don't want to further expand on that yet until we get the case closed and done. I don't believe he even knows English (small central EU country), but just to make sure he and us both get what we deserve.

 

[pioneerguy600]

Is the ring pin stop in the wrong place, or is that an optical delusion ?

You would not see the ring ends in the exhaust port normally.

 

[Tobystihl]

Looks like incorrect ring thickness looking at the lands, usually caused by using genuine rings in an aftermarket piston!

 

[KittycatUsingPowertools]

Looks like incorrect ring thickness looking at the lands, usually caused by using genuine rings in an aftermarket piston!

There was one Caber ring and one unmarked ring on the AM piston.

 

[pioneerguy600]

There was one Caber ring and one unmarked ring on the AM piston.

Which one broke, the Caber or unmarked one?

 

[pioneerguy600]

When I see a ring catch and break like this one did I think there was not enough ring end gap, the ring expanded with heat and bulged into the exhaust port. Had that happen on a buddies 394 he put together himself.

 

[pioneerguy600]

Thanks y'all again for the comments and understanding the crappy situation we are in. Sadly, yesterday the saw decided to self destruct. Contacted the seller, after some back and fort he ghosted me. Unlucky for him, we have jurist's and such in our family and friend group and will pursue him that way. We ran the saw on 100 octane rated fuel (we only have 95 and 100 fuel here) and Stihl HP ultra oil 1:40, RPM calibrated to factory settings with tachometer. About used 20 liters of fuel while the saw was with us during this past 2 weeks before loud bang and stalling instantly.

My main question at this point, can anyone identify the machine by the serial number? Last picture attached showing serial. Is there maybe a dedicated thread on the forums to ask for a lookup? I saw there were sites which no longer work. I will call our local Stihl repair shop tomorrow to see if they can identify the saw themselves as well, because our case would be even stronger against him sprinkled with fraud if it turns out the saw was 650 and not a 660 what we were sold.

Also another question, because it has been mentioned before in other threads as well, what is exactly the vacuum and pressure test? How is it done exactly?

I do not think the 9 digit and lower serial numbers can not be decoded any more, the data base has been erased or lost, Stihl could decode 10 digit serial numbers last time I seen posts including them. Measure the cylinder bore, that usually tells the story or post a complete pic of the saws exterior features, both sides top and bottom. When you get the clutch off the oil pump can tell the model between a 064 and a 066 but I think the oil pump on a 066 and / MS660 looks the same as the MS650.

 

[Mad Professor]

When I see a ring catch and break like this one did I think there was not enough ring end gap, the ring expanded with heat and bulged into the exhaust port. Had that happen on a buddies 394 he put together himself.

But a Hyway cylinder catching a ring does not surprise me.

How does chamfer on top of port look? Hard to tell with the damage, but on either side I don't see much.

Also mixing and matching AM parts you better measure EVERYTHING. Good idea even with OEM.

 

[pioneerguy600]

But a Hyway cylinder catching a ring does not surprise me.

How does chamfer on top of port look? Hard to tell with the damage, but on either side I don't see much.

Also mixing and matching AM parts you better measure EVERYTHING. Good idea even with OEM.

Once you go AM most all common things like port shapes, bevels around the port ring size and skirt clearances all go haywire. Squish clearances are all over the place, usually much greater than OEM. The roof of the exhaust port can often be too flat across, not enough arch,not enough bevel to tuck rings back in. Have often seen where the rings have worn away at the upper edge of a ex port due to the fore mentioned but to catch and break a ring lie the ops the ring has to be hanging out a good distance, The engine ran a fair long time,20 liters is close to 5 gallons of fuel so I figure the cylinder was good enough to run for a while before the ring popped out extensively like a heavy heating scenario would cause. Just a guess really as I don`t have the items here in my hands to examine.

 

[pioneerguy600]

But a Hyway cylinder catching a ring does not surprise me.

How does chamfer on top of port look? Hard to tell with the damage, but on either side I don't see much.

Also mixing and matching AM parts you better measure EVERYTHING. Good idea even with OEM.

I went back and took a closer look at the exhaust port, the roof is quite flat but there appears to be a bevel from what I can make out, I only use a .010 bevel on my own saws after porting, that has been sufficient for my personal saws, if I port for others I increase that bevel to more like .015 as the saw may be used for milling or other high heat applications. My port shape would most likely be a bit more arch also.

 

[KittycatUsingPowertools]

Which one broke, the Caber or unmarked one?

The Caber one, which was the bottom ring. But maybe if the unmarked one was the bottom, that would have caught the edge the same way eventually. Hubby saw the moment we got it out the box that the cylinder was new, so he ran through a few liters of gas first, letting it cool in between, basically heat cycling it, because we were unsure about the other parts if they are new or not.

I do not think the 9 digit and lower serial numbers can not be decoded any more, the data base has been erased or lost, Stihl could decode 10 digit serial numbers last time I seen posts including them. Measure the cylinder bore, that usually tells the story or post a complete pic of the saws exterior features, both sides top and bottom. When you get the clutch off the oil pump can tell the model between a 064 and a 066 but I think the oil pump on a 066 and / MS660 looks the same as the MS650.

Our local official Stihl shop could identify the machine as a 660. But I heavily think at this point this thing is a frankensaw. Basically everything that matters inside are all AM, oil pump, clutch, P&C, probably the crankshaft as well, we haven't checked that, and probably won't for a while since opening the case against the seller means we need to hand over the machine to someone who can officially say that we were lied to about the state of the machine.

But it truly looks frankensaw, the crankcase's halves have a different wear and chip marks and discoloration, we found an OEM MS 044 annular buffer in one of the holes, the washer under the clutch was just an simple washer drilled up to size badly, and a myriad of other problems I can't even keep up with. Only good parts have been so far are the rewind, carburetor and throttle, those are OEM and in a fairly good shape.

 

[pioneerguy600]

The Caber one, which was the bottom ring. But maybe if the unmarked one was the bottom, that would have caught the edge the same way eventually. Hubby saw the moment we got it out the box that the cylinder was new, so he ran through a few liters of gas first, letting it cool in between, basically heat cycling it, because we were unsure about the other parts if they are new or not.

Our local official Stihl shop could identify the machine as a 660. But I heavily think at this point this thing is a frankensaw. Basically everything that matters inside are all AM, oil pump, clutch, P&C, probably the crankshaft as well, we haven't checked that, and probably won't for a while since opening the case against the seller means we need to hand over the machine to someone who can officially say that we were lied to about the state of the machine.

But it truly looks frankensaw, the crankcase's halves have a different wear and chip marks and discoloration, we found an OEM MS 044 annular buffer in one of the holes, the washer under the clutch was just an simple washer drilled up to size badly, and a myriad of other problems I can't even keep up with. Only good parts have been so far are the rewind, carburetor and throttle, those are OEM and in a fairly good shape.

Thanks for the answer, your saw has definitely been messed with, very little of it has not been apart and stuck back together with poor quality parts. Usually if the crankcases have been separated one can see the new replacement gasket sticking out between the halves at the front of the chassis, new gaskets usually need to be trimmed flush after assembly. Possibly the original gasket was reused with a dab of sealer applied or not. Definitely too much damage or bad parts to deal with at this point, hope you can get some resolve from this nightmare.

 

[KittycatUsingPowertools]

Thanks for the answer, your saw has definitely been messed with, very little of it has not been apart and stuck back together with poor quality parts. Usually if the crankcases have been separated one can see the new replacement gasket sticking out between the halves at the front of the chassis, new gaskets usually need to be trimmed flush after assembly. Possibly the original gasket was reused with a dab of sealer applied or not. Definitely too much damage or bad parts to deal with at this point, hope you can get some resolve from this nightmare.

Yeah, the gasket is sticking out, AM gasket sets are like 3$ here, so the franken maker might have used a new one, but obviously everything is possible at this point sadly.

If our plan works out, we are going to get a quote on repairs with OEM parts from the official service center and a letter from a lawyer, that if he doesn't pay, we are going to file an official report at the police and go to court.